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Paramagnetic Spin Seebeck Effect
NASA Astrophysics Data System (ADS)
Wu, Stephen M.; Pearson, John E.; Bhattacharya, Anand
We report the observation of the longitudinal spin Seebeck effect in paramagnetic insulators. By using a microscale on-chip local heater, we generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. Using this technique at low temperatures (<20 K ), we resolve the paramagnetic spin Seebeck effect in the insulating paramagnets Gd3Ga5O12 (gadolinium gallium garnet) and DyScO3 (DSO), using either W or Pt as the spin detector layer. By taking advantage of the strong magnetocrystalline anisotropy of DSO, we eliminate contributions from the Nernst effect in W or Pt, which produces a phenomenologically similar signal.
Paramagnetic spin seebeck effect.
Wu, Stephen M; Pearson, John E; Bhattacharya, Anand
We report the observation of the longitudinal spin Seebeck effect in paramagnetic insulators. By using a microscale on-chip local heater, we generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. Using this technique at low temperatures (<20??K), we resolve the paramagnetic spin Seebeck effect in the insulating paramagnets Gd_{3}Ga_{5}O_{12} (gadolinium gallium garnet) and DyScO_{3} (DSO), using either W or Pt as the spin detector layer. By taking advantage of the strong magnetocrystalline anisotropy of DSO, we eliminate contributions from the Nernst effect in W or Pt, which produces a phenomenologically similar signal. PMID:26001014
Time resolved spin Seebeck effect experiments
Roschewsky, Niklas, E-mail: firstname.lastname@example.com; Schreier, Michael; Schade, Felix; Ganzhorn, Kathrin; Meyer, Sibylle; Geprõgs, Stephan [Walther-Mei▀ner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Kamra, Akashdeep [Walther-Mei▀ner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Huebl, Hans; Goennenwein, Sebastian T. B. [Walther-Mei▀ner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Nanosystems Initiative Munich (NIM), Munich (Germany); Gross, Rudolf [Walther-Mei▀ner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, Technische Universitõt M³nchen, Garching (Germany); Nanosystems Initiative Munich (NIM), Munich (Germany)
In this Letter, we present the results of transient thermopower experiments, performed at room temperature on yttrium iron garnet/platinum bilayers. Upon application of a time-varying thermal gradient, we observe a characteristic low-pass frequency response of the ensuing thermopower voltage with cutoff frequencies of up to 37 MHz. We interpret our results in terms of the spin Seebeck effect, and argue that small wavevector magnons are of minor importance for the spin Seebeck effect in our thin film hybrid structures.
Seebeck effect at the atomic scale.
Lee, Eui-Sup; Cho, Sanghee; Lyeo, Ho-Ki; Kim, Yong-Hyun
The atomic variations of electronic wave functions at the surface and electron scattering near a defect have been detected unprecedentedly by tracing thermoelectric voltages given a temperature bias [Cho et al., Nat. Mater. 12, 913 (2013)]. Because thermoelectricity, or the Seebeck effect, is associated with heat-induced electron diffusion, how the thermoelectric signal is related to the atomic-scale wave functions and what the role of the temperature is at such a length scale remain very unclear. Here we show that coherent electron and heat transport through a pointlike contact produces an atomic Seebeck effect, which is described by the mesoscopic Seebeck coefficient multiplied by an effective temperature drop at the interface. The mesoscopic Seebeck coefficient is approximately proportional to the logarithmic energy derivative of local density of states at the Fermi energy. We deduced that the effective temperature drop at the tip-sample junction could vary at a subangstrom scale depending on atom-to-atom interaction at the interface. A computer-based simulation method of thermoelectric images is proposed, and a point defect in graphene was identified by comparing experiment and the simulation of thermoelectric imaging. PMID:24745445
Large Seebeck effect by charge-mobility engineering.
Sun, Peijie; Wei, Beipei; Zhang, Jiahao; Tomczak, Jan M; Strydom, A M; S°ndergaard, M; Iversen, Bo B; Steglich, Frank
The Seebeck effect describes the generation of an electric potential in a conducting solid exposed to a temperature gradient. In most cases, it is dominated by an energy-dependent electronic density of states at the Fermi level, in line with the prevalent efforts towards superior thermoelectrics through the engineering of electronic structure. Here we demonstrate an alternative source for the Seebeck effect based on charge-carrier relaxation: a charge mobility that changes rapidly with temperature can result in a sizeable addition to the Seebeck coefficient. This new Seebeck source is demonstrated explicitly for Ni-doped CoSb3, where a marked mobility change occurs due to the crossover between two different charge-relaxation regimes. Our findings unveil the origin of pronounced features in the Seebeck coefficient of many other elusive materials characterized by a significant mobility mismatch. When utilized appropriately, this effect can also provide a novel route to the design of improved thermoelectric materials. PMID:26108283
Large Seebeck effect by charge-mobility engineering
Sun, Peijie; Wei, Beipei; Zhang, Jiahao; Tomczak, Jan M.; Strydom, A.M.; S°ndergaard, M.; Iversen, Bo B.; Steglich, Frank
The Seebeck effect describes the generation of an electric potential in a conducting solid exposed to a temperature gradient. In most cases, it is dominated by an energy-dependent electronic density of states at the Fermi level, in line with the prevalent efforts towards superior thermoelectrics through the engineering of electronic structure. Here we demonstrate an alternative source for the Seebeck effect based on charge-carrier relaxation: a charge mobility that changes rapidly with temperature can result in a sizeable addition to the Seebeck coefficient. This new Seebeck source is demonstrated explicitly for Ni-doped CoSb3, where a marked mobility change occurs due to the crossover between two different charge-relaxation regimes. Our findings unveil the origin of pronounced features in the Seebeck coefficient of many other elusive materials characterized by a significant mobility mismatch. When utilized appropriately, this effect can also provide a novel route to the design of improved thermoelectric materials. PMID:26108283
Giant spin Seebeck effect in a non-magnetic material.
Jaworski, C M; Myers, R C; Johnston-Halperin, E; Heremans, J P
The spin Seebeck effect is observed when a thermal gradient applied to a spin-polarized material leads to a spatially varying transverse spin current in an adjacent non-spin-polarized material, where it gets converted into a measurable voltage. It has been previously observed with a magnitude of microvolts per kelvin in magnetically ordered materials, ferromagnetic metals, semiconductors and insulators. Here we describe a signal in a non-magnetic semiconductor (InSb) that has the hallmarks of being produced by the spin Seebeck effect, but is three orders of magnitude larger (millivolts per kelvin). We refer to the phenomenon that produces it as the giant spin Seebeck effect. Quantizing magnetic fields spin-polarize conduction electrons in semiconductors by means of Zeeman splitting, which spin-orbit coupling amplifies by a factor of ?25 in InSb. We propose that the giant spin Seebeck effect is mediated by phonon-electron drag, which changes the electrons' momentum and directly modifies the spin-splitting energy through spin-orbit interactions. Owing to the simultaneously strong phonon-electron drag and spin-orbit coupling in InSb, the magnitude of the giant spin Seebeck voltage is comparable to the largest known classical thermopower values. PMID:22785317
Longitudinal spin Seebeck effect: from fundamentals to applications.
Uchida, K; Ishida, M; Kikkawa, T; Kirihara, A; Murakami, T; Saitoh, E
The spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in ferromagnetic or ferrimagnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin-orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This 'longitudinal spin Seebeck effect' (LSSE) has been observed in various sample systems and exclusively established by separating the spin-current contribution from extrinsic artefacts, such as conventional thermoelectric and magnetic proximity effects. The LSSE in insulators also provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin-Hall effects. In this paper, we review basic experiments on the LSSE and discuss its potential thermoelectric applications with several demonstrations. PMID:25105889
Longitudinal spin Seebeck effect: from fundamentals to applications
NASA Astrophysics Data System (ADS)
Uchida, K.; Ishida, M.; Kikkawa, T.; Kirihara, A.; Murakami, T.; Saitoh, E.
The spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in ferromagnetic or ferrimagnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin-orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This ælongitudinal spin Seebeck effectÆ (LSSE) has been observed in various sample systems and exclusively established by separating the spin-current contribution from extrinsic artefacts, such as conventional thermoelectric and magnetic proximity effects. The LSSE in insulators also provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin-Hall effects. In this paper, we review basic experiments on the LSSE and discuss its potential thermoelectric applications with several demonstrations.
Evaluation of thermal gradients in longitudinal spin Seebeck effect measurements
NASA Astrophysics Data System (ADS)
Sola, A.; Kuepferling, M.; Basso, V.; Pasquale, M.; Kikkawa, T.; Uchida, K.; Saitoh, E.
In the framework of the longitudinal spin Seebeck effect (LSSE), we developed an experimental setup for the characterization of LSSE devices. This class of device consists in a layered structure formed by a substrate, a ferrimagnetic insulator (YIG) where the spin current is thermally generated, and a paramagnetic metal (Pt) for the detection of the spin current via the inverse spin-Hall effect. In this kind of experiments, the evaluation of a thermal gradient through the thin YIG layer is a crucial point. In this work, we perform an indirect determination of the thermal gradient through the measurement of the heat flux. We developed an experimental setup using Peltier cells that allow us to measure the heat flux through a given sample. In order to test the technique, a standard LSSE device produced at Tohoku University was measured. We find a spin Seebeck SSSE coefficient of 2.8 ū 10 - 7 V K-1.
Enhanced thermoelectric performance and anomalous seebeck effects in topological insulators.
Xu, Yong; Gan, Zhongxue; Zhang, Shou-Cheng
Improving the thermoelectric figure of merit zT is one of the greatest challenges in material science. The recent discovery of topological insulators (TIs) offers new promise in this prospect. In this work, we demonstrate theoretically that zT is strongly size dependent in TIs, and the size parameter can be tuned to enhance zT to be significantly greater than 1. Furthermore, we show that the lifetime of the edge states in TIs is strongly energy dependent, leading to large and anomalous Seebeck effects with an opposite sign to the Hall effect. These striking properties make TIs a promising material for thermoelectric science and technology. PMID:24949782
Measuring spin diffusion length using spin Seebeck effect
NASA Astrophysics Data System (ADS)
Kannan, Harsha; Fan, Xin; Xiao, John
Ever since its discovery, spin Seebeck effect (SSE) has attracted plenty of attention. The conversion from thermal gradient to spin current has shown great potential in thermal energy harvesting. SSE can also be utilized as a source to generate pure spin current to unveil new physics. Here we show that it is possible to measure spin diffusion length of a heavy metal Pt by studying the SSE as a function of Pt layer thickness. The SSE signal first increases, peaks, and then decreases with increasing Pt layer thickness. By fitting with a drift-diffusion model, we obtain the spin diffusion length of Pt to be about 2nm, close to that obtained from other techniques. Moreover, we can insert a thin layer of Cu in order to remove the possible proximity effect. Similar spin-diffusion length is obtained from this measurement.
Flexible thermoelectric films using the spin Seebeck effect
NASA Astrophysics Data System (ADS)
Kirihara, Akihiro; Ishida, Masahiko; Someya, Hiroko; Kondo, Koichi; Yamamoto, Naoharu; Uchida, Ken-Ichi; Saitoh, Eiji; Kohmoto, Shigeru; Murakami, Tomoo
Thermoelectric (TE) technologies have been of great interest, since they can directly generate electricity from thermal energy that is available in various places. For making full use of such omnipresent heat, TE devices using the spin Seebeck effect (SSE) potentially open opportunities for large-area TE applications, because of their favorable features such as a simple film structure and convenient scaling capability. In this work, we show a SSE-based flexible TE device, which consists of metallic and magnetic-insulator films on a 25-um-thick polyimide substrate. Novel fabrication processes enabled us to form the magnetic insulator, having a good spin-current-conduction property for the SSE, on the highly flexible organic film. Such flexible TE sheets are readily implementable on various curved or uneven surfaces, leading to versatile energy-harvesting and heat-sensing applications.
Thermoelectric Seebeck effect in oxide-based resistive switching memory
NASA Astrophysics Data System (ADS)
Wang, Ming; Bi, Chong; Li, Ling; Long, Shibing; Liu, Qi; Lv, Hangbing; Lu, Nianduan; Sun, Pengxiao; Liu, Ming
Reversible resistive switching induced by an electric field in oxide-based resistive switching memory shows a promising application in future information storage and processing. It is believed that there are some local conductive filaments formed and ruptured in the resistive switching process. However, as a fundamental question, how electron transports in the formed conductive filament is still under debate due to the difficulty to directly characterize its physical and electrical properties. Here we investigate the intrinsic electronic transport mechanism in such conductive filament by measuring thermoelectric Seebeck effects. We show that the small-polaron hopping model can well describe the electronic transport process for all resistance states, although the corresponding temperature-dependent resistance behaviours are contrary. Moreover, at low resistance states, we observe a clear semiconductor-metal transition around 150?K. These results provide insight in understanding resistive switching process and establish a basic framework for modelling resistive switching behaviour.
Thermoelectric Seebeck effect in oxide-based resistive switching memory.
Wang, Ming; Bi, Chong; Li, Ling; Long, Shibing; Liu, Qi; Lv, Hangbing; Lu, Nianduan; Sun, Pengxiao; Liu, Ming
Reversible resistive switching induced by an electric field in oxide-based resistive switching memory shows a promising application in future information storage and processing. It is believed that there are some local conductive filaments formed and ruptured in the resistive switching process. However, as a fundamental question, how electron transports in the formed conductive filament is still under debate due to the difficulty to directly characterize its physical and electrical properties. Here we investigate the intrinsic electronic transport mechanism in such conductive filament by measuring thermoelectric Seebeck effects. We show that the small-polaron hopping model can well describe the electronic transport process for all resistance states, although the corresponding temperature-dependent resistance behaviours are contrary. Moreover, at low resistance states, we observe a clear semiconductor-metal transition around 150?K. These results provide insight in understanding resistive switching process and establish a basic framework for modelling resistive switching behaviour. PMID:25141267
Thermoelectric Seebeck effect in oxide-based resistive switching memory
Wang, Ming; Bi, Chong; Li, Ling; Long, Shibing; Liu, Qi; Lv, Hangbing; Lu, Nianduan; Sun, Pengxiao; Liu, Ming
Reversible resistive switching induced by an electric field in oxide-based resistive switching memory shows a promising application in future information storage and processing. It is believed that there are some local conductive filaments formed and ruptured in the resistive switching process. However, as a fundamental question, how electron transports in the formed conductive filament is still under debate due to the difficulty to directly characterize its physical and electrical properties. Here we investigate the intrinsic electronic transport mechanism in such conductive filament by measuring thermoelectric Seebeck effects. We show that the small-polaron hopping model can well describe the electronic transport process for all resistance states, although the corresponding temperature-dependent resistance behaviours are contrary. Moreover, at low resistance states, we observe a clear semiconductor¢metal transition around 150?K. These results provide insight in understanding resistive switching process and establish a basic framework for modelling resistive switching behaviour. PMID:25141267
Seebeck effects in a graphene nanoribbon coupled to two ferromagnetic leads
NASA Astrophysics Data System (ADS)
Zhou, Benhu; Zhou, Benliang; Zeng, Yangsu; Zhou, Guanghui; Ouyang, Tao
We theoretically investigate the Seebeck effects for the system of a narrow graphene nanoribbon between two ferromagnetic (FM) electrodes with noncollinear magnetic moments. Both zigzag-edge graphene nanoribbons (ZGNRs) and armchair-edge graphene nanoribbons (AGNRs) have been considered. By using the nonequilibrium Green's function method combining with the tight-binding Hamiltonian, it is demonstrated that, the Seebeck coefficients are sensitive to the chirality and width of the nanoribbon in the absence of magnetic field. Compared with 22-ZGNR and metallic 17-AGNR systems, semiconducting 15-AGNR system is found to posses superior thermoelectric performance, its Seebeck coefficients can be improved by two orders of magnitude. Meanwhile, the Seebeck coefficients for both 22-ZGNR and metallic 17-AGNR systems are the same order as that of graphene system. Furthermore, the Seebeck coefficients are strongly dependent on the magnetization M as well as magnetic configuration of the two FM leads. Particularly, the Seebeck coefficient drastically enhances when the magnetization of the two FM leads is in antiparallel configuration. Interestingly, the Seebeck coefficient for both 22-ZGNR and metallic 17-AGNR systems increases with increasing temperature T, while it decreases with increasing T for semiconducting 15-AGNR system. Moreover, the dependence Seebeck coefficients on magnetic flux ? show an oscillation behavior. The results obtained here may provide a valuable theoretical guidance to experimentally design heat spintronic devices.
Interplay of Peltier and Seebeck effects in nanoscale nonlocal spin valves.
Bakker, F L; Slachter, A; Adam, J-P; van Wees, B J
We have experimentally studied the role of thermoelectric effects in nanoscale nonlocal spin valve devices. A finite element thermoelectric model is developed to calculate the generated Seebeck voltages due to Peltier and Joule heating in the devices. By measuring the first, second, and third harmonic voltage response nonlocally, the model is experimentally examined. The results indicate that the combination of Peltier and Seebeck effects contributes significantly to the nonlocal baseline resistance. Moreover, we found that the second and third harmonic response signals can be attributed to Joule heating and temperature dependencies of both the Seebeck coefficient and resistivity. PMID:21230794
Large spin Seebeck effects in zigzag-edge silicene nanoribbons
NASA Astrophysics Data System (ADS)
Yang, Xi-Feng; Liu, Yu-Shen; Feng, Jin-Fu; Wang, Xue-Feng
Using the first-principles methods, we investigate the thermospin properties of a two-probe model based on zigzag-edge silicene nanoribbons (ZSiNRs). Compared with the odd-width ZSiNRs, the spin Seebeck coefficient of the even-width ZSiNRs is obviously enhanced at room temperature. This fact is attributed to a nearly perfect symmetry of the linear conductance gap with the different spin index with respect to the Fermi level induced by the different parity of the wave functions. More interestingly, the corresponding charge Seebeck coefficient is near zero. Therefore, when a thermal bias is presented in the even-width ZSiNRs, a nearly pure spin current is achieved. Meanwhile, the spin polarization of the current approaches infinite.
Observation of the spin Seebeck effect in epitaxial Fe3O4 thin films
NASA Astrophysics Data System (ADS)
Ramos, R.; Kikkawa, T.; Uchida, K.; Adachi, H.; Lucas, I.; Aguirre, M. H.; Algarabel, P.; Morell¾n, L.; Maekawa, S.; Saitoh, E.; Ibarra, M. R.
We report the experimental observation of the spin Seebeck effect in magnetite thin films. The signal observed at temperatures above the Verwey transition is a contribution from both the anomalous Nernst (ANE) and spin Seebeck (SSE) effects. The contribution from the ANE of the Fe3O4 layer to the SSE is found to be negligible due to the resistivity difference between Fe3O4 and Pt layers. Below the Verwey transition, the SSE is free from the ANE of the ferromagnetic layer and it is also found to dominate over the ANE due to magnetic proximity effect on the Pt layer.
Photo-Seebeck effect in tetragonal PbO single crystals
Mondal, P. S.; Okazaki, R.; Taniguchi, H.; Terasaki, I. [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)
We report the observation of photo-Seebeck effect in tetragonal PbO crystals. The photo-induced carriers contribute to the transport phenomena, and consequently the electrical conductivity increases and the Seebeck coefficient decreases with increasing photon flux density. A parallel-circuit model is used to evaluate the actual contributions of photo-excited carriers from the measured transport data. The photo-induced carrier concentration estimated from the Seebeck coefficient increases almost linearly with increasing photon flux density, indicating a successful photo-doping effect on the thermoelectric property. The mobility decreases by illumination but the reduction rate strongly depends on the illuminated photon energy. Possible mechanisms of such photon-energy-dependent mobility are discussed.
Modelling of Seebeck effect in electron beam deep welding of dissimilar metals
Marek Ziolkowski; Hartmut Brauer
Purpose ¢ The purpose of this paper is to present a 3D model of deep welding of dissimilar metals and to show how to model the electron beam deflection due to thermoelectric fields caused by temperature gradients in some dissimilar metals (Seebeck effect). Design\\/methodology\\/approach ¢ A 3D thermoelectric and heat conduction model is used to estimate the deflection of the
Communication Enhancing the Seebeck effect in carbon fiber-reinforced cement by using
Chung, Deborah D.L.
carbon fibers Sihai Wen, D.D.L. Chung* Composite Materials Research Laboratory, State University of New (Ridgefield, CT). This type of carbon fiber is quite graphitic, thereby allowing intercalation to occurCommunication Enhancing the Seebeck effect in carbon fiber-reinforced cement by using intercalated
Data Acquisition and Virtual Instrumentation system for the study of Peltier and Seebeck effects
Florin SANDU; Venetia SANDU; Stefan NAN; Adrian Iulian DUMITRU
The paper presents the development of a data acquisition system dedicated to the study of Peltier and Seebeck effect and to the performance parameters of a commercial thermoelectric semiconductor element. It was used a National Instruments NI USB-6008 Data Acquisition System (connected to National Semiconductor LM35 temperature sensors) to build a Virtual Instrumentation system programmed in NI LabView. There are
Application of the Seebeck effect for monitoring of neutron embrittlement and low-cycle fatigue in nuclear reactor steel
M. Niffenegger; K. Reichlin; D. Kalkhof
The monitoring of neutron embrittlement and low-cycle fatigue in nuclear reactor steel is an important topic in lifetime extension of nuclear power plants. Among several material parameters that may change due to material degradation are the thermoelectric properties. Therefore, we investigated the application of the Seebeck effect for determining material degradation of common reactor pressure vessel (RPV) steel. The Seebeck
Extracting the effective mass of electrons in transparent conductive oxide thin films using Seebeck coefficient
Wang, Yaqin; Zhu, Junhao; Tang, Wu, E-mail: email@example.com [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)
A method is proposed that combines Seebeck coefficient and carrier concentration to determine the electron effective mass of transparent conductive oxide (TCO) thin films. Experiments were conducted to test the validity of this approach on the transparent conductive Ga-doped ZnO thin films deposited by magnetron sputtering. An evident agreement of the calculated electron effective mass of the films is observed between the proposed approach and the previous studies. Besides, the optical carrier concentration and mobility derived from the calculated electron effective mass and spectroscopic ellipsometry using a complex dielectric function are consistent with those from direct Hall-effect measurement. The agreements suggest that Seebeck coefficient can serve as an alternative tool for extracting the effective mass of electrons in TCO films.
On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect
Boehnke, Alexander; Milnikel, Marius; von der Ehe, Marvin; Franz, Christian; Zbarsky, Vladyslav; Czerner, Michael; Rott, Karsten; Thomas, Andy; Heiliger, Christian; Reiss, G³nter; M³nzenberg, Markus
Thermoelectric effects in magnetic tunnel junctions are promising to serve as the basis for logic devices or memories in a ögreenö information technology. However, up to now the readout contrast achieved with Seebeck effects was magnitudes smaller compared to the well-established tunnel magnetoresistance effect. Here, we resolve this problem by demonstrating that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic ō1ö state and off to ō0ö by simply changing the magnetic state of the CoFeB electrodes. This new functionality is achieved by combining a thermal gradient and an electric field. Our results show that the signal crosses zero and can be adjusted by tuning a bias voltage that is applied between the electrodes of the junction; hence, the name of the effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and energy-dependent transmission of electrons in the junction, the bTMS effect can be configured using the bias voltage with much higher control than the tunnel magnetoresistance and even completely suppressed for only one magnetic configuration. Moreover, our measurements are a step towards the experimental realization of high TMS ratios without additional bias voltage, which are predicted for specific Co-Fe compositions. PMID:25755010
Magnon spin-current theory for the longitudinal spin-Seebeck effect
NASA Astrophysics Data System (ADS)
Rezende, S. M.; RodrĒguez-Sußrez, R. L.; Cunha, R. O.; Rodrigues, A. R.; Machado, F. L. A.; Fonseca Guerra, G. A.; Lopez Ortiz, J. C.; Azevedo, A.
We present a theoretical model for the longitudinal spin-Seebeck effect (LSSE) in bilayers made of a ferromagnetic insulator (FMI), such as yttrium iron garnet (YIG), and a normal metal (NM), such as platinum (Pt), that relies on the bulk magnon spin current created by the temperature gradient across the thickness of the FMI. We show that the spin current pumped into the NM layer by the magnon accumulation in the FMI provides continuity of the spin current at the FMI/NM interface and is essential for the existence of the longitudinal spin-Seebeck effect. The results of the theory are in good agreement with experimental data for the variation of the LSSE with the sample temperature and with the FMI layer thickness in YIG/Pt bilayers.
Model for the Spin Seebeck Effect in InSb in a Magnetic Field
NASA Astrophysics Data System (ADS)
Pike, Nicholas; Stroud, David
The spin Seebeck effect is the generation of a voltage due to spin currents in the presence of a temperature gradient. We have developed a theory for this effect in the semiconductor InSb in a magnetic field. We consider spin- 1 / 2 electrons in the conduction band of InSb with a temperature gradient parallel to the applied magnetic field. A Boltzmann equation approach leads to a spin current parallel to the field and proportional to the temperature gradient. The spin-orbit interaction induces a canting of the electronic spin which produces an electric field perpendicular to the temperature gradient via the inverse spin Hall effect. This effect is measured in experiments as the spin Seebeck coefficient. We find that the spin current exhibits oscillations as a function of magnetic field which arise when the Fermi energy crosses the bottom of a Landau band. These oscillations resemble those seen in measurements of the spin Seebeck coefficient in the semiconductor InSb. This work was supported by the Center for Emerging Materials at The Ohio State University, an NSF MRSEC (Grant No. DMR0820414).
The Third Way of Thermal-Electric Conversion beyond Seebeck and Pyroelectric Effects
Ren, Jie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Thermal-electric conversion is crucial for smart energy control and harvesting, such as thermal sensing and waste heat recovering. So far, people are aware of only two ways of direct thermal-electric conversion, Seebeck and pyroelectric effects, each with distinct working conditions and limitations. Here, we report the third way of thermal-electric conversion beyond Seebeck and pyroelectric effects. In contrast to Seebeck effect that requires spatial temperature difference, the-third-way converts the time-dependent ambient temperature fluctuation into electricity, similar to the behavior of pyroelectricity. However, the-third-way is also distinct from pyroelectric effect in the sense that it does not require polar materials but applies to general conducting systems. We demonstrate that the-third-way results from the temperature-fluctuation-induced dynamical charge redistribution. It is a consequence of the fundamental nonequilibrium thermodynamics and has a deep connection to the topological phase in quantum mechanics. Our findings expand our knowledge and provide new means of thermal-electric energy harvesting.
Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions
NASA Astrophysics Data System (ADS)
Liu, Yu-Shen; Zhang, Xue; Feng, Jin-Fu; Wang, Xue-Feng
We propose a high-efficiency thermospin device constructed by a carbon atomic chain sandwiched between two ferromagnetic (FM) zigzag graphene nanoribbon electrodes. In the low-temperature regime, the magnitude of the spin figure of merit is nearly equal to that of the corresponding charge figure of merit. This is attributed to the appearances of spin-resolved Fano resonances in the linear conductance spectrum resulting from the quantum interference effects between the localized states and the expanded states. The spin-dependent Seebeck effect is obviously enhanced near these Fano resonances with the same spin index; meanwhile, the Seebeck effect of the other spin component has a smaller value due to the smooth changing of the linear conductance with the spin index. Thus, a large spin Seebeck effect is achieved, and the magnitude of the spin figure of merit can reach 1.2 at T = 25 K. Our results indicate that the FM graphene-carbon-chain junctions can be used to design the high-efficiency thermospin devices.
Magneto-Seebeck effect in R FeAsO (R =rare earth) compounds: Probing the magnon drag scenario
NASA Astrophysics Data System (ADS)
Caglieris, F.; Braggio, A.; Pallecchi, I.; Provino, A.; Pani, M.; Lamura, G.; Jost, A.; Zeitler, U.; Galleani D'Agliano, E.; Manfrinetti, P.; Putti, M.
We investigate the Seebeck effect in R FeAsO (R =rare earth) compounds as a function of temperature and magnetic field up to 30 T. The Seebeck curves are characterized by a broad negative bump around 50 K, which is sample dependent and strongly enhanced by the application of a magnetic field. A model for the temperature and field dependence of the magnon drag contribution to the Seebeck effect by antiferromagnetic (AFM) spin fluctuation is developed. It accounts for the magnitude and scaling properties of such bump feature in our experimental data in LaFeAsO. This analysis accounts for the apparent inconsistency of literature Seebeck effect data on these compounds and has the potential to extract precious information on the coupling between electrons and AFM spin fluctuations in these parent compound systems, with implications on the pairing mechanism of the related superconducting compounds.
Effect of phonon transport on the Seebeck coefficient and thermal conductivity of silicon nanowire arrays
NASA Astrophysics Data System (ADS)
Sadhu, Jyothi Swaroop
Thermoelectrics enable solid-state conversion of heat to electricity by the Seebeck effect, but must provide scalable and cost-effective technology for practical waste heat harvesting. This dissertation explores the thermoelectric properties of electrochemically etched silicon nanowires through experiments, complemented by charge and thermal transport theories. Electrolessly etched silicon nanowires show anomalously low thermal conductivity that has been attributed to the increased scattering of heat conducting phonons from the surface disorder introduced by etching. The reduction is below the incoherent limit for phonon scattering at the boundary, the so-called Casimir limit. A new model of partially coherent phonon transport shows that correlated multiple scattering of phonons off resonantly matched rough surfaces can indeed lead to thermal conductivity below the Casimir limit. Using design guidelines from the theory, silicon nanowires of controllable surface roughness are fabricated using metal-assisted chemical etching. Extensive characterization of the nanowire surfaces using transmission electron microscopy provides surface roughness parameters that are important in testing transport theories. The second part of the dissertation focuses on the implications of increased phonon scattering on the Seebeck coefficient, which is a cumulative effect of non-equilibrium amongst charge carriers and phonons. A novel frequency-domain technique enables simultaneous measurements of the Seebeck coefficient and the thermal conductivity of nanowire arrays. The frequency response measurements isolate the parasitic contributions thus improving upon existing techniques for cross-plane thermoelectric measurements. While the thermal conductivity of nanowires reduces significantly with increased roughness, there is also a significant reduction in the Seebeck coefficient over a wide range of doping. Theoretical fitting of the data reveals that such reduction results from the annihilation of phonon drag in nanowires due to phonon boundary scattering. By exploring the effect of surface roughness and employing lattice non-equilibrium theories, the measurements are able to distinguish between long wavelength phonons that contribute to phonon drag and shorter wavelengths that contribute to heat conduction near room temperature. Phonon drag quenching in nanostructures has implications beyond silicon and this thesis paves the way toward spectrally selective phonon scattering for improving nanoscale thermoelectrics.
Spin-dependent Seebeck effect and spin caloritronics in magnetic graphene
NASA Astrophysics Data System (ADS)
Rameshti, Babak Zare; Moghaddam, Ali G.
We investigate the spin-dependent thermoelectric effects in magnetic graphene in both diffusive and ballistic regimes. Employing the Boltzmann and Landauer formalisms we calculate the spin and charge Seebeck coefficients (thermopower) in magnetic graphene varying the spin splitting, temperature, and doping of the junction. It is found that while in normal graphene the temperature gradient drives a charge current, in the case of magnetic graphene a significant spin current is also established. In particular we show that in the undoped magnetic graphene in which different spin carriers belong to conduction and valence bands, a pure spin current is driven by the temperature gradient. In addition it is revealed that profound thermoelectric effects can be achieved at intermediate easily accessible temperatures when the thermal energy is comparable with Fermi energy kBT ?? . By further investigation of the spin-dependent Seebeck effect and a significantly large figure of merit for spin thermopower ZspT , we suggest magnetic graphene as a promising material for spin-caloritronics studies and applications.
Enhanced spin Seebeck effect in a germanene p-n junction
NASA Astrophysics Data System (ADS)
Zheng, Jun; Chi, Feng; Guo, Yong
Spin Seebeck effect in a germanene p-n junction is studied by using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian. We find that the thermal bias ?T can generate spin thermopower when a local exchange field is applied on one edge of the germanene nano-ribbon. The magnitude of the spin thermopower can be modulated by the potential drop across the two terminals of the p-n junction. When the value of the potential drop is smaller than the spin-orbit interaction strength, the spin thermopower is enhanced by two orders of magnitude larger as compared to the case of zero p-n voltage. Optimal temperature corresponding to maximum spin thermopower is insensitive to the potential drop. In the p-n region, maximum spin thermopower can be obtained at relatively higher temperatures. When the value of the potential drop is larger than that of the spin-orbit interaction, however, the spin Seebeck effect decays rapidly with increasing potential drop or temperature. By optimizing the structure parameters, the magnitude of the spin thermopower can be remarkably enhanced due to the coexistence of the exchange field and the potential drop.
Asymmetric and Negative Differential Thermal Spin Effect at Magnetic Interfaces: Towards Spin Seebeck Diodes and Transistors
NASA Astrophysics Data System (ADS)
Ren, Jie; Zhu, Jian-Xin
We study the nonequilibrium thermal-spin transport across metal-magnetic insulator interfaces. The transport is assisted by the exchange interaction between conduction electrons in the metal and localized spins in the magnetic insulator. We predict the rectification and negative differential spin Seebeck effect (SSE), that is, reversing the temperature bias is able to give asymmetric spin currents and increasing temperature bias could give an anomalously decreasing spin current. We resolve their microscopic mechanism as a consequence of the energy-dependent electronic DOS in the metal. The rectification of spin Peltier effect is also discussed. We then study the asymmetric and negative differential magnon tunneling driven by temperature bias. We show that the many-body magnon interaction that makes the magnonic spectrum temperature-dependent is the crucial factor for the emergence of rectification and negative differential SSEs in magnon tunneling junctions. We show that these asymmetric and negative differential SSEs are relevant for building magnon and spin Seebeck diodes and transistors, which could play important roles in controlling information and energy in functional devices. Supported by the National Nuclear Security Administration of the US DOE at LANL under Contract No. DE-AC52-06NA25396.
Investigation of the magnetic properties of insulating thin films using the longitudinal spin Seebeck effect
NASA Astrophysics Data System (ADS)
Kehlberger, A.; Jakob, G.; Onbasli, M. C.; Kim, D. H.; Ross, C. A.; Klõui, M.
The longitudinal spin Seebeck effect is used as a detector for the magnetic properties and switching characteristics of magnetic thin insulating films. We use a 300 nm and a 20 nm thick Yttrium Iron Garnet (YIG, Y3Fe5O12) film prepared by pulsed laser deposition and afterwards coated by platinum for the detection of the thermally excited magnons by the inverse spin Hall effect. The inverse spin Hall signals reveal a magnetic uniaxial anisotropy along the direction of the platinum stripe in the thicker film. For the thin film we find a more isotropic behavior, which is complementarily observed using the magnetoresistance occurring at the platinum/YIG interface. We explain our results on the basis of x-ray diffraction data, which reveal a miscut of the substrate and film surface and an expansion of the YIG lattice. Both findings favor a growth-induced magnetic anisotropy that we observe.
Hot-Carrier Seebeck Effect: Diffusion and Remote Detection of Hot Carriers in Graphene.
Sierra, Juan F; Neumann, Ingmar; Costache, Marius V; Valenzuela, Sergio O
We investigate hot carrier propagation across graphene using an electrical nonlocal injection/detection method. The device consists of a monolayer graphene flake contacted by multiple metal leads. Using two remote leads for electrical heating, we generate a carrier temperature gradient that results in a measurable thermoelectric voltage VNL across the remaining (detector) leads. Due to the nonlocal character of the measurement, VNL is exclusively due to the Seebeck effect. Remarkably, a departure from the ordinary relationship between Joule power P and VNL, VNL ? P, becomes readily apparent at low temperatures, representing a fingerprint of hot-carrier dominated thermoelectricity. By studying VNL as a function of bias, we directly determine the carrier temperature and the characteristic cooling length for hot-carrier propagation, which are key parameters for a variety of new applications that rely on hot-carrier transport. PMID:25950746
Spin Seebeck effect in thin films of the Heusler compound Co2MnSi
NASA Astrophysics Data System (ADS)
Bosu, S.; Sakuraba, Y.; Uchida, K.; Saito, K.; Ota, T.; Saitoh, E.; Takanashi, K.
The recently discovered spin Seebeck effect (SSE) which generates spin voltage due to a temperature gradient in ferromagnets, was systematically studied in half-metallic Heusler compound Co2MnSi (CMS)/Pt thin films to investigate the effect of spin polarization of ferromagnetic layer on SSE. An epitaxial thin film of CMS with an almost perfect B2-ordered structure was prepared directly on a MgO(001) substrate. The measurement was performed at room temperature for various temperature differences, ?T = 0-20 K between higher (300 K+?T) and lower (300 K) temperature ends along the film. The clear sign reversal of the thermally induced spin voltage due to SSE at the higher and lower temperature ends of the CMS film was detected by means of inverse spin-Hall effect in a Pt wire. The SSE was also investigated in a Py thin film deposited on a MgO(001) substrate and compared to that with CMS to verify the effect of spin polarization on SSE. Comparable signals of SSE in CMS and Py thin films suggested that thermal excitation of magnons might have more vital effects in SSE than the degree of spin polarization in ferromagnetic metals.
Spin-dependent Seebeck effect in asymmetric four-terminal systems with Rashba spin-orbit coupling
NASA Astrophysics Data System (ADS)
Zhou, Jun; Wang, Biao; Li, Mengjie; Nakayama, Tsuneyoshi; Li, Baowen
We propose a new type of spin-dependent Seebeck effect (SDSE) emerging from the Rashba spin-orbit coupling in asymmetric four-terminal electron systems. This system generates spin currents or spin voltages along the longitudinal direction parallel to the temperature gradient in the absence of magnetic fields. The remarkable result arises from the breaking of the reflection symmetry along the transverse direction. In the meantime, the SDSE along the transverse direction, the so-called the spin Nernst effect, with spin currents or spin voltages perpendicular to the temperature gradient, can be simultaneously realized in our system. We further find that it is possible to use the temperature differences between four leads to tune the spin-dependent Seebeck coefficients.
Unambiguous separation of the inverse spin Hall and anomalous Nernst effects within a ferromagnetic metal using the spin Seebeck effect
Wu, Stephen M., E-mail: email@example.com; Hoffman, Jason; Pearson, John E.; Bhattacharya, Anand [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
The longitudinal spin Seebeck effect is measured on the ferromagnetic insulator Fe{sub 3}O{sub 4} with the ferromagnetic metal Co{sub 0.2}Fe{sub 0.6}B{sub 0.2} (CoFeB) as the spin detector. By using a non-magnetic spacer material between the two materials (Ti), it is possible to decouple the two ferromagnetic materials and directly observe pure spin flow from Fe{sub 3}O{sub 4} into CoFeB. It is shown that in a single ferromagnetic metal, the inverse spin Hall effect (ISHE) and anomalous Nernst effect (ANE) can occur simultaneously with opposite polarity. Using this and the large difference in the coercive fields between the two magnets, it is possible to unambiguously separate the contributions of the spin Seebeck effect from the ANE and observe the degree to which each effect contributes to the total response. These experiments show conclusively that the ISHE and ANE in CoFeB are separate phenomena with different origins and can coexist in the same material with opposite response to a thermal gradient.
Cahaya, Adam B.; Tretiakov, O. A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Bauer, Gerrit E. W. [Institute for Materials Research and WPI-AIMR, Tohoku University, Sendai 980-8577 (Japan); Kavli Institute of NanoScience, TU Delft Lorentzweg 1, 2628 CJ Delft (Netherlands)
We derive expressions for the efficiency and figure of merit of two spin caloritronic devices based on the spin Seebeck effect (SSE), i.e., the generation of spin currents by a temperature gradient. The inverse spin Hall effect is conventionally used to detect the SSE and offers advantages for large area applications. We also propose a device that converts spin current into electric one by means of a spin-valve detector, which scales favorably to small sizes and approaches a figure of merit of 0.5 at room temperature.
Platinum thickness dependence and annealing effect of the spin-Seebeck voltage in platinum/yttrium iron garnet structures
NASA Astrophysics Data System (ADS)
Saiga, Yuta; Mizunuma, Kotaro; Kono, Yasushi; Ryu, Jeong Chun; Ono, Hiroshi; Kohda, Makoto; Okuno, Eiichi
We investigate the substrate annealing effect of thermoelectric voltage induced by the spin-Seebeck effect in Pt/polycrystalline yttrium iron garnet Y3Fe5O12 (YIG) structures with different Pt thicknesses. The thermoelectric voltage is increased by decreasing the Pt thickness to 1.9 nm as well as by annealing. Annealing at 1073 K for 5 h enhances the thermoelectric voltage up to 7.4 ĄV/K in structures with 1.9 nm Pt thickness.
Uchida, K; Xiao, J; Adachi, H; Ohe, J; Takahashi, S; Ieda, J; Ota, T; Kajiwara, Y; Umezawa, H; Kawai, H; Bauer, G E W; Maekawa, S; Saitoh, E
Thermoelectric generation is an essential function in future energy-saving technologies. However, it has so far been an exclusive feature of electric conductors, a situation which limits its application; conduction electrons are often problematic in the thermal design of devices. Here we report electric voltage generation from heat flowing in an insulator. We reveal that, despite the absence of conduction electrons, the magnetic insulator LaY(2)Fe(5)O(12) can convert a heat flow into a spin voltage. Attached Pt films can then transform this spin voltage into an electric voltage as a result of the inverse spin Hall effect. The experimental results require us to introduce a thermally activated interface spin exchange between LaY(2)Fe(5)O(12) and Pt. Our findings extend the range of potential materials for thermoelectric applications and provide a crucial piece of information for understanding the physics of the spin Seebeck effect. PMID:20871606
Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers.
Lee, Kyeong-Dong; Kim, Dong-Jun; Yeon Lee, Hae; Kim, Seung-Hyun; Lee, Jong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Lee, Ki-Suk; Song, Hyon-Seok; Sohn, Jeong-Woo; Shin, Sung-Chul; Park, Byong-Guk
The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devices. PMID:26020492
Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers
Lee, Kyeong-Dong; Kim, Dong-Jun; Yeon Lee, Hae; Kim, Seung-Hyun; Lee, Jong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Lee, Ki-Suk; Song, Hyon-Seok; Sohn, Jeong-Woo; Shin, Sung-Chul; Park, Byong-Guk
The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devices. PMID:26020492
Half-metallic properties, single-spin negative differential resistance, and large single-spin Seebeck effects induced by chemical doping in zigzag-edged graphene nanoribbons
NASA Astrophysics Data System (ADS)
Yang, Xi-Feng; Zhou, Wen-Qian; Hong, Xue-Kun; Liu, Yu-Shen; Wang, Xue-Feng; Feng, Jin-Fu
Ab initio calculations combining density-functional theory and nonequilibrium Green's function are performed to investigate the effects of either single B atom or single N atom dopant in zigzag-edged graphene nanoribbons (ZGNRs) with the ferromagnetic state on the spin-dependent transport properties and thermospin performances. A spin-up (spin-down) localized state near the Fermi level can be induced by these dopants, resulting in a half-metallic property with 100% negative (positive) spin polarization at the Fermi level due to the destructive quantum interference effects. In addition, the highly spin-polarized electric current in the low bias-voltage regime and single-spin negative differential resistance in the high bias-voltage regime are also observed in these doped ZGNRs. Moreover, the large spin-up (spin-down) Seebeck coefficient and the very weak spin-down (spin-up) Seebeck effect of the B(N)-doped ZGNRs near the Fermi level are simultaneously achieved, indicating that the spin Seebeck effect is comparable to the corresponding charge Seebeck effect.
Thermal properties of magnons and the spin Seebeck effect in yttrium iron garnet/normal metal hybrid structures
NASA Astrophysics Data System (ADS)
Rezende, S. M.; RodrĒguez-Sußrez, R. L.; Lopez Ortiz, J. C.; Azevedo, A.
In the study of the spin Seebeck effect (SSE) in structures with a ferromagnetic insulator (FMI) in contact with a normal metal it is important to know the distributions of the temperatures of the magnon, phonon, and electron systems. Studies of the SSE in yttrium iron garnet (YIG) have relied on the thermal properties of magnons in YIG calculated with expressions valid for low temperatures. Here we present a calculation of the magnon specific heat and thermal conductivity in YIG and show that the values at room temperature are very discrepant from numbers used in the literature. With our values we calculate the temperature profiles of the magnon and phonon systems in a FMI subject to a temperature gradient in the configurations used to study the transverse and longitudinal SSE. In both cases the results are quite different from those obtained in previous studies.
High temperature Seebeck coefficient metrology
Martin, J. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Tritt, T. [Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 (United States); Uher, C. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)
We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectric measurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.
High temperature Seebeck coefficient metrology
Martin, J.; Tritt, T.; Uher, Ctirad
We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential propertymeasurement for evaluating the potential performance of novel thermoelectricmaterials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectricmeasurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.
Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction.
Boehnke, Alexander; Walter, Marvin; Roschewsky, Niklas; Eggebrecht, Tim; Drewello, Volker; Rott, Karsten; M³nzenberg, Markus; Thomas, Andy; Reiss, G³nter
Recently, several groups have reported spin-dependent thermoelectric effects in magnetic tunnel junctions. In this paper, we present a setup for time-resolved measurements of thermovoltages and thermocurrents of a single micro- to nanometer-scaled tunnel junction. An electrically modulated diode laser is used to create a temperature gradient across the tunnel junction layer stack. This laser modulation technique enables the recording of time-dependent thermovoltage signals with a temporal resolution only limited by the preamplifier for the thermovoltage. So far, time-dependent thermovoltage could not be interpreted. Now, with the setup presented in this paper, it is possible to distinguish different Seebeck voltage contributions to the overall measured voltage signal in the ?s time regime. A model circuit is developed that explains those voltage contributions on different sample types. Further, it will be shown that a voltage signal arising from the magnetic tunnel junction can only be observed when the laser spot is directly centered on top of the magnetic tunnel junction, which allows a lateral separation of the effects. PMID:23822355
Spin-dependent Seebeck Effect, Thermal Colossal Magnetoresistance and Negative Differential Thermoelectric Resistance in Zigzag Silicene Nanoribbon Heterojunciton.
Fu, Hua-Hua; Wu, Dan-Dan; Zhang, Zu-Quan; Gu, Lei
Spin-dependent Seebeck effect (SDSE) is one of hot topics in spin caloritronics, which examine the relationships between spin and heat transport in materials. Meanwhile, it is still a huge challenge to obtain thermally induced spin current nearly without thermal electron current. Here, we construct a hydrogen-terminated zigzag silicene nanoribbon heterojunction, and find that by applying a temperature difference between the source and the drain, spin-up and spin-down currents are generated and flow in opposite directions with nearly equal magnitudes, indicating that the thermal spin current dominates the carrier transport while the thermal electron current is much suppressed. By modulating the temperature, a pure thermal spin current can be achieved. Moreover, a thermoelectric rectifier and a negative differential thermoelectric resistance can be obtained in the thermal electron current. Through the analysis of the spin-dependent transport characteristics, a phase diagram containing various spin caloritronic phenomena is provided. In addition, a thermal magnetoresistance, which can reach infinity, is also obtained. Our results put forward an effective route to obtain a spin caloritronic material which can be applied in future low-power-consumption technology. PMID:26000658
Effect of Magnetic Doping on Electrical and Thermal Conductivities and Seebeck Coefficient of Suspended Bismuth Telluride Nanoplates
NASA Astrophysics Data System (ADS)
Jo, Insun; Thompson Pettes, Michael; Yao, Zhen; Shi, Li
Bismuth telluride has been investigated intensively as a model system for topological insulators. In this work, we have studied electrical and thermal transport properties of suspended bismuth telluride nanoplates grown by the vapor-solid method. The thin crystals were transferred onto micro-fabricated suspended structures with built-in electrodes and thermometers, which allowed us to measure electrical (?) and thermal (?) conductivities as well as the Seebeck coefficient (S) . The through-etched hole in the devices enabled us to evaporate Cr layers on both surfaces of the crystal. After H2 annealing at 500 K, we measured enhanced ?, ?, and S values by 40, 10, and 20%, respectively. In comparison, H2 annealing without Cr evaporation resulted in 10, 10, and -8% changes of ?, ?, and S values, respectively. The effect of magnetic doping by Cr will be discussed. Additionally, magneto-transport measurements were performed on the samples to resolve the transport properties of the surface states. We observed a pronounced weak anti-localization feature in undoped samples. Changes in this feature after Cr doping will be presented.
Nanoscale Spin Seebeck Rectifier: Controlling Thermal Spin Transport across Insulating Magnetic Junctions with Localized Spin
NASA Astrophysics Data System (ADS)
Ren, Jie; Fransson, Jonas; Zhu, Jian-Xin
The spin Seebeck effect is studied across a charge insulating magnetic junction, in which thermal-spin conjugate transport is assisted by the exchange interactions between the localized spin in the center and electrons in metallic leads. We show that, in contrast with bulk spin Seebeck effect, the figure of merit of such nanoscale thermal-spin conversion can be infinite, leading to the ideal Carnot efficiency in the linear response regime. We also find that in the nonlinear spin Seebeck transport regime the device possesses the asymmetric and negative differential spin Seebeck effects. In the last, the situations with leaking electron tunneling are also discussed. This nanoscale thermal spin rectifier, by tuning the junction parameters, can act as a spin Seebeck diode, spin Seebeck transistor, and spin Seebeck switch, which could have substantial implications for flexible thermal and information control in molecular spin caloritronics.
The Seebeck coefficient of iodine
Perez-Fernandez, Domingo Miguel
THE SEEBECK COEFFICIENT OF IODINE A Thesis By DOMINGO M. PEREZ-F~EZ Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE January 1968 Major Subject...; Physics THE SEEBECK COEFFICIENT OF IODINE A Thesis By DOMINGO M. PEREZ-FERNANDEZ Approved as to style and content by: ( airman of Co ittee) (Member) (Head of Depa ment) (Member) ( ember) (Member) (Member) January 1968 ACKNONLEDGEMENTS...
Uncertainty analysis for common Seebeck and electrical resistivity measurement systems.
Mackey, Jon; Dynys, Frederick; Sehirlioglu, Alp
This work establishes the level of uncertainty for electrical measurements commonly made on thermoelectric samples. The analysis targets measurement systems based on the four probe method. Sources of uncertainty for both electrical resistivity and Seebeck coefficient were identified and evaluated. Included are reasonable estimates on the magnitude of each source, and cumulative propagation of error. Uncertainty for the Seebeck coefficient includes the cold-finger effect which has been quantified with thermal finite element analysis. The cold-finger effect, which is a result of parasitic heat transfer down the thermocouple probes, leads to an asymmetric over-estimation of the Seebeck coefficient. A silicon germanium thermoelectric sample has been characterized to provide an understanding of the total measurement uncertainty. The electrical resistivity was determined to contain uncertainty of ▒7.0% across any measurement temperature. The Seebeck coefficient of the system is +1.0%/-13.1% at high temperature and ▒1.0% near room temperature. The power factor has a combined uncertainty of +7.3%/-27.0% at high temperature and ▒7.5% near room temperature. These ranges are calculated to be typical values for a general four probe Seebeck and resistivity measurement configuration. PMID:25173324
Spin Seebeck devices using local on-chip heating
NASA Astrophysics Data System (ADS)
Wu, Stephen M.; Fradin, Frank Y.; Hoffman, Jason; Hoffmann, Axel; Bhattacharya, Anand
A micro-patterned spin Seebeck device is fabricated using an on-chip heater. Current is driven through a Au heater layer electrically isolated from a bilayer consisting of Fe3O4 (insulating ferrimagnet) and a spin detector layer. It is shown that through this method it is possible to measure the longitudinal spin Seebeck effect (SSE) for small area magnetic devices, equivalent to traditional macroscopic SSE experiments. Using a lock-in detection technique, it is possible to more sensitively characterize both the SSE and the anomalous Nernst effect (ANE), as well as the inverse spin Hall effect in various spin detector materials. By using the spin detector layer as a thermometer, we can obtain a value for the temperature gradient across the device. These results are well matched to values obtained through electromagnetic/thermal modeling of the device structure and with large area spin Seebeck measurements.
Thermal and transport properties of the Heusler-type Fe2VAl1-xGex(0?x?0.20) alloys: Effect of doping on lattice thermal conductivity, electrical resistivity, and Seebeck coefficient
NASA Astrophysics Data System (ADS)
Nishino, Y.; Deguchi, S.; Mizutani, U.
We report on the thermoelectric properties of the Heusler-type Fe2VAl1-xGex alloys with compositions 0?x?0.20 . While Fe2VAl(x=0) exhibits a semiconductorlike behavior in electrical resistivity, a slight substitution of Ge for Al causes a significant decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient, reaching -130?V/K for x=0.05 at around room temperature. Comparison with the Fe2VAl1-xSix system demonstrates that the compositional variation of the Seebeck coefficient falls on a universal curve irrespective of the doping elements (Ge and Si), both of which are isoelectronic elements. The net effect of doping is most likely to cause a rigid-bandlike shift of the Fermi level from the central region in the pseudogap. In spite of a similar decrease in the electrical resistivity with composition of Ge and Si, the thermal conductivity decreases more rapidly for the Ge substitution. It is concluded that doping of heavier atoms such as Ge reduces more effectively the lattice thermal conductivity while retaining the low electrical resistivity as well as the large Seebeck coefficient.
Data analysis for Seebeck coefficient measurements.
de Boor, J; M³ller, E
The Seebeck coefficient is one of the key quantities of thermoelectric materials and routinely measured in various laboratories. There are, however, several ways to calculate the Seebeck coefficient from the raw measurement data. We compare these different ways to extract the Seebeck coefficient, evaluate the accuracy of the results, and show methods to increase this accuracy. We furthermore point out experimental and data analysis parameters that can be used to evaluate the trustworthiness of the obtained result. The shown analysis can be used to find and minimize errors in the Seebeck coefficient measurement and therefore increase the reliability of the measured material properties. PMID:23822373
The Seebeck coefficient of superionic conductors
NASA Astrophysics Data System (ADS)
Mahan, G. D.
We present a theory of the anomalous Seebeck coefficient found in the superionic conductor Cu2Se. It has a phase transition at T = 400 K where the cations disorder but the anions do not. This disorder gives a temperature-dependent width to the electronic states in the conduction band. This width provides the anomalous Seebeck contribution.
Optimum design of a nanoscale spin-Seebeck power device
NASA Astrophysics Data System (ADS)
Liao, Tianjun; Lin, Jian; Su, Guozhen; Lin, Bihong; Chen, Jincan
A theoretical model of a nanoscale spin-Seebeck power device (SSPD) is proposed based on the longitudinal spin-Seebeck effect in bilayers made of a ferromagnetic insulator and a normal metal. Expressions for the power output and thermal efficiency of the SSPD are derived analytically. The performance characteristics of the nanoscale SSPD are analyzed using numerical simulation. The maximum power output density and efficiency are calculated numerically. The effect of the spin Hall angle on the performance characteristics of the SSPD is analyzed. The choice of materials and the structure of the device are discussed. The optimum criteria of some key parameters of the SSPD, such as the power output density, efficiency, thickness of the normal metal, and the load resistance, are given. The results obtained here could provide a theoretical basis for the optimal design and operation of nanoscale SSPDs.
Seebeck coefficient of nanostructured phosphorus-alloyed bismuth telluride thick films
J. Zhou; S. Li; H. M. A. Soliman; M. S. Toprak; M. Muhammed; D. Platzek; E. M³ller
Nanostructured phosphorous-alloyed Bi2Te3 thick films have been prepared by electrochemical deposition. The average grain size of the films was calculated to be 14¢26nm based on Scherrer's equation. The effect of P on the Seebeck coefficient of the Bi2Te3 thick film was investigated. The results show that P-alloyed thick film has n-type conductivity with the Seebeck coefficient of ?35?V\\/K. The correlation
Apparatus Measures Seebeck Coefficient And Resistivity
NASA Technical Reports Server (NTRS)
Zoltan, Leslie D.; Wood, Charles; Fleurial, Jean-Pierre; Liu, Yixin
Electrical measurements made by four point probes, two of which double as temperature probes. Laboratory apparatus measures both Seebeck coefficients and electrical resistivities of candidate thermoelectric materials at temperatures from ambient to 1,300 K. Apparatus makes possible to take both measurements alternately and in rapid succession during same heating cycle, thereby reducing distortion.
Seebeck coefficient of nanowires interconnected into large area networks.
Pennelli, Giovanni; Totaro, Massimo; Piotto, Massimo; Bruschi, Paolo
We measured the macroscopic Seebeck coefficient of silicon nanowires (SiNWs), organized in a highly interconnected networks on large areas (order of mm(2)). The fabricated networks are very reliable with respect to random nanowire failure and are electrically and thermally equivalent to many SiNWs placed in parallel between the electrical contacts. The equivalent SiNWs have a macroscopic length of the order of millimeters and are very narrow (width smaller than 100 nm) so that they can be used to exploit thermoelectric properties at nanoscale for macroscopic electrical power generation and/or cooling. The measurement of the Seebeck coefficient S, facilitated by the macroscopic dimensions of the network, gives an insight into two questions, nanowire effective doping and carrier mobility, which are widely discussed in the literature. We found that the measured value of S is compatible with an effective doping that is higher than that of the original wafer. This higher doping is consistent with the value estimated from the measured electrical conductivity of the SiNWs with the assumption that the electron mobility inside the nanowire is equal to that of bulk silicon. PMID:23668777
Combination of PVA with Graphene to Improve the Seebeck Coefficient for Thermoelectric Generator Applications
NASA Astrophysics Data System (ADS)
Mahmoud, L.; Abdul Samad, Y.; Alhawari, M.; Mohammad, B.; Liao, K.; Ismail, M.
Ultrasensitive thermoelectric (TE) materials are essential for the next generation of self-powered electronic devices. In this work, a graphene-based TE generator was fabricated. For 50 to 1000 graphene layers the average Seebeck coefficient was 90 ?V/K. We also report improvement of the Seebeck coefficient by use of a hybrid material containing 10% poly(vinyl alcohol) (PVA) and 90% graphene oxide prepared and tested under the same conditions. The results show that the Seebeck coefficient is improved by an average of 30% compared with graphene alone. Because the fabrication process is facile, scalable, and cost effective, it could also be applicable to other fields of science and engineering.
Description of a Sensitive Seebeck Calorimeter Used for Cold Fusion Studies
NASA Astrophysics Data System (ADS)
Storms, Edmund
A sensitive and stable Seebeck calorimeter is described and used to determine the heat of formation of PdD. This determination can be used to show that such calorimeters are sufficiently accurate to measure the LENR effect and give support to the claims.
System to Measure Thermal Conductivity and Seebeck Coefficient for Thermoelectrics
NASA Technical Reports Server (NTRS)
Kim, Hyun-Jung; Skuza, Jonathan R.; Park, Yeonjoon; King, Glen C.; Choi, Sang H.; Nagavalli, Anita
The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at elevated temperatures. This has led to the implementation of nonstandardized practices that have further complicated the confirmation of reported high ZT materials. The major objective of the procedure described is for the simultaneous measurement of the Seebeck coefficient and thermal diffusivity within a given temperature range. These thermoelectric measurements must be precise, accurate, and reproducible to ensure meaningful interlaboratory comparison of data. The custom-built thermal characterization system described in this NASA-TM is specifically designed to measure the inplane thermal diffusivity, and the Seebeck coefficient for materials in the ranging from 73 K through 373 K.
Seebeck and Peltier coefficients of hydrogen electrodes related to the
Kjelstrup, Signe
Seebeck and Peltier coefficients of hydrogen electrodes related to the PEMFC Papy Zefaniya Chemical. Abstract The coefficient of Thermoelectric power of hydrogen electrode as function of partial pressure has
Simultaneous measurements of Seebeck coefficient and thermal conductivity across superlattice
NASA Astrophysics Data System (ADS)
Yang, B.; Liu, J. L.; Wang, K. L.; Chen, G.
A method is developed to simultaneously measure the Seebeck coefficient and thermal conductivity in the cross-plane direction of thin films and applied to an n-type Si/Ge quantum-dot superlattice. In this method, an Au/Cr pattern serves as both a heater and a thermometer, and a microprobe is prepared between the heater and the thin film to extract the Seebeck voltage. Using a differential measurement between the thin films with different thickness, the temperature and voltage drops across the thin film are determined to deduce its cross-plane thermal conductivity and Seebeck coefficient. At room temperature, the cross-plane Seebeck coefficient and thermal conductivity are 312 ?V/K and 2.92 W/mK, respectively, for the n-type Si(75 ┼)/Ge(15 ┼) quantum-dot superlattice doped to 8.7ū1019 cm-3.
The impact of commonly used approximations on the computation of the Seebeck coefficient and mobility of polar semiconductors
NASA Astrophysics Data System (ADS)
Ramu, Ashok T.; Bowers, John E.
Seebeck coefficient modeling and measurement has important applications in direct thermal to electrical energy conversion and solid-state physics. The computations of the Seebeck coefficient and mobility of polar semiconductors in the literature often employ certain approximations, notably the relaxation time approximation (RTA) and the truncation of the Boltzmann transport equation. We study the accuracy of these approximations as a function of the effective mass, temperature, and carrier concentration using a recently developed technique for rigorous solution of the Boltzmann transport equation. We find that the approximations give rise to considerable error in the computed Seebeck coefficients of heavily doped semiconductors with a low effective mass, and that the RTA is entirely inapplicable for the accurate computation of the mobility of several important materials.
Calculation of Phonon Conductivity and Seebeck Coefficient in Cu-Ni Alloy
NASA Astrophysics Data System (ADS)
Konishi, Yusuke; Asai, Yoshihiro
In recent years, thermoelectric materials have been attracting a lot of attention because they are expected to be applied for utilization of waste heat. Many kinds of materials are studied for this purpose; semiconductors, alloys, organic materials, etc. In 2010, a giant Peltier effect was observed in a Cu-Ni/Au junction. It is considered that this giant Peltier effect is caused by nano-scale phase separation formed in the sputtering process. Although this material is a great candidate for a thermoelectric material, we need to find the condition for a large thermoelectric coefficient that requires a large Seebeck coefficient, large electric conductivity, and small phonon conductivity. We calculated phonon conductivity in Cu-Ni alloy by using nonequilibrium molecular dynamics simulation and calculated Seebeck coefficients via ab-initio methods.
Nanoscale Thermoelectrics: A Study of the Absolute Seebeck Coefficient of Thin Films
NASA Astrophysics Data System (ADS)
Mason, Sarah J.
The worlds demand for energy is ever increasing. Likewise, the environmental impact of climate change due generating that energy through combustion of fossil fuels is increasingly alarming. Due to these factors new sources of renewable energies are constantly being sought out. Thermoelectric devices have the ability to generate clean, renewable, energy out of waste heat. However promising that is, their inefficiency severely inhibits applicability and practical use. The usefulness of a thermoelectric material increases with the dimensionless quantity, ZT, which depends on the Seebeck coefficient and electrical and thermal conductivity. These characteristic material parameters have interdependent energy transport contributions that classically prohibit the optimization of one with out the detriment of another. Encouraging advancements of ZT have occurred in the past ten years due to the decoupling of the thermal and electrical conductivity. Further advancements are necessary in order to produce applicable devices. One auspicious way of decoupling or tuning energy transport properties, is through size reduction to the nanoscale. However, with reduced dimensions come complications in measuring material properties. Measurements of properties such as the Seebeck coefficient, S, are primarily contingent upon the measurement apparatus. The Seebeck coefficient is defined as the amount of voltage generated by a thermal gradient. Measuring a thermally generated voltage by traditional methods gives, the voltage measured as a linear function of the Seebeck coefficient of the leads and of the material being tested divided by the applied thermal gradient. If accurate values of the Seebeck coefficients of the leads are available, simple subtraction provides the answer. This is rarely the case in nanoscale measurement devices with leads exclusively made from thin film materials that do not have well known bulk-like thermopower values. We have developed a technique to directly measure, S, as a function of temperature using a micro-machined thermal isolation platform consisting of a suspended, patterned SiN membrane. By measuring a series of thicknesses of metallic films up to the infinitely thin film limit, in which the electrical resistivity is no longer decreasing with increasing film thickness, but still not at bulk values, along with the effective electron mean free path, we are able to show the contribution of the leads needed to measure this property. Having a comprehensive understanding of the background contribution we are able to determine the absolute Seebeck coefficient of a wide variety of thin films. The nature of the design of the SiN membrane also allows the ability to accurately and directly measure thermal and electrical transport of the thin films yielding a comprehensive measurement of the three quantities that characterize a material's efficiency. This can serve to further the development of thermoelectric materials through precise measurements of the material properties that dictate efficiency.
Seebeck Coefficient Metrology: Do Contemporary Protocols Measure Up?
NASA Astrophysics Data System (ADS)
Martin, Joshua; Wong-Ng, Winnie; Green, Martin L.
Comparative measurements of the Seebeck coefficient are challenging due to the diversity of instrumentation and measurement protocols. With the implementation of standardized measurement protocols and the use of Standard Reference Materials (SRMs«), for example, the recently certified National Institute of Standards and Technology (NIST) SRM« 3451 ``Low Temperature Seebeck Coefficient Standard (10-390 K)'', researchers can reliably analyze and compare data, both intra- and inter-laboratory, thereby accelerating the development of more efficient thermoelectric materials and devices. We present a comparative overview of commonly adopted Seebeck coefficient measurement practices. First, we examine the influence of asynchronous temporal and spatial measurement of electric potential and temperature. Temporal asynchronicity introduces error in the absolute Seebeck coefficient of the order of ?10%, whereas spatial asynchronicity introduces error of the order of a few percent. Second, we examine the influence of poor thermal contact between the measurement probes and the sample. This is especially critical at high temperature, wherein the prevalent mode of measuring surface temperature is facilitated by pressure contact. Each topic will include the comparison of data measured using different measurement techniques and using different probe arrangements. We demonstrate that the probe arrangement is the primary limit to high accuracy, wherein the Seebeck coefficients measured by the 2-probe arrangement and those measured by the 4-probe arrangement diverge with the increase in temperature, approaching ?14% at 900 K. Using these analyses, we provide recommended measurement protocols to guide members of the thermoelectric materials community in performing more accurate measurements and in evaluating more comprehensive uncertainty limits.
Seebeck coefficient measurements on Li, Sn, Ta, Mo, and W
NASA Astrophysics Data System (ADS)
Fiflis, P.; Kirsch, L.; Andruczyk, D.; Curreli, D.; Ruzic, D. N.
The thermopower of W, Mo, Ta, Li and Sn has been measured relative to stainless steel, and the Seebeck coefficient of each of these materials has then been calculated. These are materials that are currently relevant to fusion research and form the backbone for different possible liquid limiter concepts including TEMHD concepts such as LiMIT. For molybdenum the Seebeck coefficient has a linear rise with temperature from SMo = 3.9 ?V K-1 at 30 ░C to 7.5 ?V K-1 at 275 ░C, while tungsten has a linear rise from SW = 1.0 ?V K-1 at 30 ░C to 6.4 ?V K-1 at 275 ░C, and tantalum has the lowest Seebeck coefficient of the solid metals studied with STa = -2.4 ?V K-1 at 30 ░C to -3.3 ?V K-1 at 275 ░C. The two liquid metals, Li and Sn have also been measured. The Seebeck coefficient for Li has been re-measured and agrees with past measurements. As seen with Li there are two distinct phases in Sn also corresponding to the solid and liquid phases of the metal. In its solid phase the SSn-solid = -1.5 ?V K-1 at 30 ░C and -2.5 ?V K-1 near the melting temperature of 231 ░C. There is a distinct increase in the Seebeck coefficient around the melting temperature as the Sn melts and stays relatively constant over the rest of the measured temperatures, SSn-melt = -1.4 ?V K-1 from 235 ░C to 275 ░C.
Exploration of thermal conductivity, Seebeck coefficient, and Lorenz number deviations in Ni-Fe alloy films
NASA Astrophysics Data System (ADS)
Zink, B. L.; Avery, A. D.; Sultan, R.; Bassett, D.; Cotteril, G.
As electronic and spintronic systems continue to shrink, exploration of the fundamental physics affecting thermal transport in prospective materials becomes increasingly essential. For example, the potential use of spin-torque driven domain wall motion in ferromagnetic nanowires as a memory element requires application of large current densities to these tiny structures. The resulting heating could have both helpful and harmful effects, and is in general not yet well-understood. This is partly due to a gap in the fundamental knowledge of thermal properties of nanoscale systems that is due to the challenging nature of the necessary measurements. We have recently developed a micromachined thermal isolation platform that allows measurement of thermal conductivity, electrical conductivity, and thermopower (or Seebeck effect) in thin film systems. In this talk we present our recent data on thermal conductivity, resistivity, and Seebeck coefficient, for Ni-Fe alloy films with thicknesses varying from 25-100 nm. We compare our results to the predictions of the Wiedemann-Franz law and discuss variations represented by deviations from the Sommerfeld value of the Lorenz number, and conclude with our plans to extend the technique to yet smaller structures. We thank the NRI-WIN and the NSF CAREER program for support.
Simultaneous Enhancement of the Electrical Conductivity and Seebeck Coefficient of PEDOT-block-PEG/SWCNTs Nanocomposites
NASA Astrophysics Data System (ADS)
Jiang, Qinglin; Liu, Congcong; Zhu, Danhua; Song, Haijun; Xu, Jingkun; Shi, Hui; Mo, Daize; Wang, Zhipeng; Zhu, Zhengyou
In this study, the thermoelectric (TE) performance of poly(3,4-ethylenedioxythiophene)-block-poly(ethylene glycol) (PEDOT-block-PEG), one of the most important poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, was studied. To improve its TE performance, different mass fractions of single-walled carbon nanotubes (SWCNTs) were incorporated by physical mixing. Blending with SWCNTs resulted in simultaneous enhancement of the electrical conductivity and Seebeck coefficient of the PEDOT-block-PEG/SWCNTs nanocomposites. At 300 K, the maximum electrical conductivity was increased from 0.51 to 78.6 S/cm, and the Seebeck coefficient was increased from 5.1 to 46.3 ?V/K. The thermal conductivity of the composite films was low (0.24-0.34 W/m/K). The maximum ZT of PEDOT-block-PEG/SWCNTs nanocomposites was 1.24 ū 10-2 when the SWCNTs content was 66.7 wt.%. This study suggests that constructing PEDOT-block-PEG/SWCNTs nanocomposites might be an effective way of improving the TE properties of PEDOT-block-PEG.
A microprobe technique for simultaneously measuring thermal conductivity and Seebeck coefficient of thin films
NASA Astrophysics Data System (ADS)
Zhang, Yanliang; Hapenciuc, Claudiu L.; Castillo, Eduardo E.; Borca-Tasciuc, Theodorian; Mehta, Rutvik J.; Karthik, Chinnathambi; Ramanath, Ganpati
We demonstrate a microprobe technique that can simultaneously measure thermal conductivity ? and Seebeck coefficient ? of thin films. In this technique, an alternative current joule-heated V-shaped microwire that serves as heater, thermometer and voltage electrode, locally heats the thin film when contacted with the surface. The ? is extracted from the thermal resistance of the microprobe and ? from the Seebeck voltage measured between the probe and unheated regions of the film by modeling heat transfer in the probe, sample and their contact area, and by calibrations with standard reference samples. Application of the technique on sulfur-doped porous Bi2Te3 and Bi2Se3 films reveals ? =-105.4 and 1.96 ?V/K, respectively, which are within 2% of the values obtained by independent measurements carried out using microfabricated test structures. The respective ? values are 0.36 and 0.52 W/mK, which are significantly lower than the bulk values due to film porosity, and are consistent with effective media theory. The dominance of air conduction at the probe-sample contact area determines the microscale spatial resolution of the technique and allows probing samples with rough surfaces.
High Temperature Seebeck Coefficient and Electrical Resistivity of Ge2Sb2Te5 Thin Films
NASA Astrophysics Data System (ADS)
Adnane, Lhacene; Dirisaglik, Faruk; Akbulut, Mustafa; Zhu, Yu; Lam, Chung; Gokirmak, Ali; Silva, Helena
Phase-change memory (PCM) is a promising memory technology in which a small volume of a chalcogenide material can be reversibly and rapidly switched between amorphous and crystalline phases by an electrical pulse that brings it above crystallization (ś 150-200 C) or melting (ś 700 C) temperature. The large temperature levels involved and small dimensions of PCM devices give rise to very large temperature gradients (ś 10 K/nm and higher) which result in strong thermoelectric effects. High-temperature characterization of the temperature-dependent thermoelectric properties of these materials is therefore critical to understand for the operation of these devices but to date there is only limited experimental data available. We have performed simultaneous measurements of Seebeck coefficient and electrical resistance of thin films of GST with different thicknesses, deposited on silicon dioxide, from room temperature to ś 600 C, under small temperature gradients. Two-point current-voltage (I-V) measurements were performed using a semiconductor parameter analyzer. The resistance of the material and the Seebeck voltage (open-circuit voltage) are calculated from the slope and intercept of the I-V characteristics. The details of the measurements and S(T) and R(T) results for the GST thin film samples will be presented and discussed.
Thermoelectric measurement equipments This instrument is designed for simultaneous measurement of Seebeck coefficient and
Taya, Minoru
electromotive force. Ę Employment of an infrared gold image heating furnace that excels in temperature method Seebeck coefficient : Static dc method Electric resistance : Four-terminal method Atmosphere Low
Thermocyclic stability of candidate Seebeck coefficient standard reference materials at high temperature
NASA Astrophysics Data System (ADS)
Martin, Joshua; Wong-Ng, Winnie; Caillat, Thierry; Yonenaga, I.; Green, Martin L.
The Seebeck coefficient is the most widely measured property specific to thermoelectric materials. There is currently no consensus on measurement protocols, and researchers employ a variety of techniques to measure the Seebeck coefficient. The implementation of standardized measurement protocols and the use of reliable Seebeck Coefficient Standard Reference Materials (SRMs«) will allow the accurate interlaboratory comparison and validation of materials data, thereby accelerating the development and commercialization of more efficient thermoelectric materials and devices. To enable members of the thermoelectric materials community the means to calibrate Seebeck coefficient measurement equipment, NIST certified SRM« 3451 "Low Temperature Seebeck Coefficient Standard (10 K to 390 K)". Due to different practical requirements in instrumentation, sample contact methodology, and thermal stability, a complementary SRM« is required for the high temperature regime (300 K to 900 K). The principal requirement of a SRM« for the Seebeck coefficient at high temperature is thermocyclic stability. We therefore characterized the thermocyclic behavior of the Seebeck coefficient for a series of candidate materials: constantan, p-type single crystal SiGe, and p-type polycrystalline SiGe, by measuring the temperature dependence of the Seebeck coefficient as a function of 10 sequential thermal cycles, between 300 K and 900 K. We employed multiple regression analysis to interpolate and analyze the thermocyclic variability in the measurement curves.
Seebeck rectification enabled by intrinsic thermoelectrical coupling in magnetic tunneling junctions.
Zhang, Z H; Gui, Y S; Fu, L; Fan, X L; Cao, J W; Xue, D S; Freitas, P P; Houssameddine, D; Hemour, S; Wu, K; Hu, C-M
An intrinsic thermoelectric coupling effect in the linear response regime of magnetic tunneling junctions (MTJ) is reported. In the dc response, it leads to a nonlinear correction to Ohm's law. Dynamically, it enables a novel Seebeck rectification and second harmonic generation, which apply for a broad frequency range and can be magnetically controlled. A phenomenological model on the footing of the Onsager reciprocal relation and the principle of energy conservation explains very well the experimental results obtained from both dc and frequency-dependent transport measurements performed up to GHz frequencies. Our work refines previous understanding of magnetotransport and microwave rectification in MTJs. It forms a new foundation for utilizing spin caloritronics in high-frequency applications. PMID:22861893
Colossal positive Seebeck coefficient and low thermal conductivity in reduced TiO2
NASA Astrophysics Data System (ADS)
Tang, Jinke; Wang, Wendong; Zhao, Guang-Lin; Li, Qiang
Reduced (oxygen deficient) single crystal TiO2 exhibits a very large positive Seebeck coefficient S at low temperature. S as large as 60 000 ĄV K-1 was observed near 10 K for the least reduced sample, which gives a thermoelectric power factor of 170 ĄW K-2 cm-1. This value is about four times higher than the power factor of Bi2Te3-based materials near room temperature. As the temperature increases the Seebeck coefficient becomes negative. The magnitude of the room temperature Seebeck coefficient, thermal conductivity and electrical resistivity decrease with the reduction of the samples. The thermal conductivity is as low as 0.83 W K-1 m-1 for the heavily reduced sample at 390 K due to phonon scattering by defect planes. The colossal Seebeck coefficient found in the materials is discussed in terms of the phonon drag of the holes.
Multifunctional probes for high-throughput measurement of Seebeck coefficient and electrical conductivity at room temperature.
GarcĒa-Ca±adas, Jorge; Min, Gao
An apparatus capable of rapid measurement of the Seebeck coefficient and electrical resistivity at room temperature is reported. The novel aspect of this apparatus is the use of 4 multifunctional probes that comprise a junction of two conductors at the tip and serve as both thermocouples and electrical contacts. In addition, one of the probes has a built-in heater that can establish a temperature gradient in the sample for the Seebeck measurement. The technique does not require special sample geometries or preparation of contacts and is suitable for bulk and thin film materials. Together with automated sample stage and data acquisition, the equipment is able to measure both the Seebeck coefficient and electrical resistivity in less than 20 s with good accuracy. Less than 5% and 4% relative errors were found for the measurement of the Seebeck coefficient and electrical resistivity, respectively. This makes the apparatus especially useful for high throughput evaluation of thermoelectric materials. PMID:24784625
Communication Seebeck effect in steel fiber reinforced cement
Chung, Deborah D.L.
Abstract Cement pastes containing short steel fibers, which contribute to electron conduction, exhibit with temperature difference (up to 65░C). In contrast, cement pastes containing short carbon fibers, which power. D 2000 Elsevier Science Ltd. All rights reserved. Keywords: Fiber reinforcement; Cement Paste
Profiling the Local Seebeck Coefficient with Nanometer Resolution Using Scanning Thermoelectric Microscopy (SThEM)
NASA Astrophysics Data System (ADS)
Lin, Yen-Hsiang; Walrath, Jenna; Goldman, Rachel
Thermoelectric (TE) devices offer a method of recovering waste heat through solid state conversion of heat to electricity. Nanostructured thermoelectric materials may provide the key to increased efficiencies, which are sensitive to the Seebeck coefficients (S) However, traditional bulk measurement techniques can only provide a spatially averaged measurement of S over the whole sample, which can hardly investigate the effects of nanostructures on S on the nanoscale. A novel technique known as scanning thermoelectric microscopy (SThEM) has recently been developed to measure induced thermal voltages with nanometer resolution In SThEM, an unheated scanning tunneling microscopy tip acts as a high-resolution voltmeter probe to measure the thermally-induced voltage, V, in a heated sample. Here we present a local S measurement using SThEM across an InGaAs P-N junction. The thermovoltage shows an abrupt change of sign within 10 nanometers, which reveals nanometer spatial resolution. We will discuss local S measurements of AlAs/GaAs superlattices (SLs) with various SL periods and compare the local S with scanning tunneling spectroscopy measurements, which will reveal how local electronic states influence thermoelectric properties. Thermoelectric (TE) devices offer a method of recovering waste heat through solid state conversion of heat to electricity. Nanostructured thermoelectric materials may provide the key to increased efficiencies, which are sensitive to the Seebeck coefficients (S) However, traditional bulk measurement techniques can only provide a spatially averaged measurement of S over the whole sample, which can hardly investigate the effects of nanostructures on S on the nanoscale. A novel technique known as scanning thermoelectric microscopy (SThEM) has recently been developed to measure induced thermal voltages with nanometer resolution In SThEM, an unheated scanning tunneling microscopy tip acts as a high-resolution voltmeter probe to measure the thermally-induced voltage, V, in a heated sample. Here we present a local S measurement using SThEM across an InGaAs P-N junction. The thermovoltage shows an abrupt change of sign within 10 nanometers, which reveals nanometer spatial resolution. We will discuss local S measurements of AlAs/GaAs superlattices (SLs) with various SL periods and compare the local S with scanning tunneling spectroscopy measurements, which will reveal how local electronic states influence thermoelectric properties. This material is based upon work primarily supported by DOE under grant No. DE-FG02-06 and ER46339 the Department of Energy under Award Number DE-PI0000012.
Extreme Seebeck anisotropy in the quasi-one-dimensional metal, Li0.9Mo6O17
NASA Astrophysics Data System (ADS)
Cohn, Joshua; Moshfeghyeganeh, Saeed; Dos Santos, Carlos A. M.; Neumeier, John J.
We present resistivity and thermopower measurements in the range 300 K <= T <= 500 K on single crystals of the quasi-one-dimensional (q1D) metal, Li0.9Mo6O17 (LiPB) transverse to the q1D metallic chains. Direct electron transfer between the chains of this material is sufficiently weak that inter-chain transport above 400 K is predominated by thermal activation of valence-band states (~ 0 . 14 eV below EF), yielding a large, p-type inter-chain Seebeck coefficient that coexists with n-type metallic behavior confined along the q1D chains. A significant Seebeck anisotropy, ?S ~= 200 ? V/K, along mutually perpendicular directions gives LiPB potential as a transverse thermoelectric. This anisotropy along with a relatively low inter-chain thermal conductivity (? ~= 2 W/mK) results in a substantial transverse Peltier effect. Work supported by the U.S. Department of Energy Office of Basic Energy Sciences (DE-FG02-12ER46888, Univ. Miami), the National Science Foundation (DMR-0907036, Mont. St. Univ.), and in Lorena by the CNPq (301334/2007-2) and FAPESP (2009/14524-6).
Dependence of Seebeck coefficient on a load resistance and energy conversion efficiency in a thermoelectric composite
Yamashita, Osamu [Materials Science Co. Ltd., 5-5-44 Minamikasugaoka, Ibaraki, Osaka 567-0046 (Japan)], E-mail: firstname.lastname@example.com; Odahara, Hirotaka [Advanced Materials Co. Ltd., 4-6-10 Kizuri, Higashiosaka, Osaka 577-0827 (Japan); Ochi, Takahiro; Satou, Kouji [Faculty of Engineering, Ehime University, Bunkyocho, Matsuyama 790-8577 (Japan)
The thermo-emf {delta}V and current {delta}I generated by imposing the alternating temperature gradients (ATG) at a period of T and the steady temperature gradient (STG) on a thermoelectric (TE) composite were measured as a function of t, where t is the lapsed time and T was varied from 60 to or {infinity} s. The STG and ATG were produced by imposing steadily and alternatively a source voltage V in the range from 1.0 to 4.0 V on two Peltier modules sandwiching a composite. {delta}T, {delta}V, {delta}I and V{sub P} oscillate at a period T and their waveforms vary significantly with a change of T, where {delta}V and V{sub P} are the voltage drops in a load resistance R{sub L} and in resistance R{sub P} of two modules. The resultant Seebeck coefficient |{alpha}| = |{delta}V|/{delta}T of a composite under the STG was found to be expressed as |{alpha}| = |{alpha}{sub 0}|(1 - R{sub comp}/R{sub T}), where R{sub T} is the total resistance of a circuit for measuring the output signals and R{sub comp} is the resistance of a composite. The effective generating power {delta}W{sub eff} has a local maximum at T = 960 s for the p-type composite and at T = 480 s for the n-type one. The maximum energy conversion efficiency {eta} of the p- and n-type composites under the ATG produced by imposing a voltage of 4.0 V at an optimum period were 0.22 and 0.23% at {delta}T{sub eff} = 50 K, respectively, which are 42 and 43% higher than those at {delta}T = 42 K under the STG. These maximum {eta} for a TE composite sandwiched between two Peltier modules, were found to be expressed theoretically in terms of R{sub P}, R{sub T}, R{sub L}, {alpha}{sub P} and {alpha}, where {alpha}{sub P} and {alpha} are the resultant Seebeck coefficients of Peltier modules and a TE composite.
A Study of the Measurement of Seebeck Coefficient of SiGe
NASA Technical Reports Server (NTRS)
Heung, King Yi
In 1821 German Physicist Thomas J. Seebeck discovered that heat could be converted into electricity when a temperature difference was applied across two points on a material. Theoretically, the generated voltage has a directly proportional relationship with the temperature difference. This relationship is the Seebeck coefficient that scientists always referred to when determining the efficiency of a thermoelectricity convention. In our experiments, however, hysteresis loops appeared when we plotted voltage against temperature difference, and the measured Seebeck appeared differently when the measurements were run under vacuum, air, and helium gas. Measurements were done by using a low-frequency AC measuring method. By simulating the experimental setup into a; thermal circuit, we found that the loop and inconsistency in measuring Seebeck coefficient could be explained by studying the behaviors of a RC circuit in a thermal sense. Under vacuum, the gap of the hysteresis loop can be largely eliminated if the time period of the temperature difference increased up to 4800s. The trend of the variations in measuring Seebeck coefficients in different environments can also be predicted by using different thermal circuit models.
In situ measurement of electrical resistivity and Seebeck coefficient simultaneously at high temperature and high pressure.
Yuan, Bao; Tao, Qiang; Zhao, Xueping; Cao, Ke; Cui, Tian; Wang, Xin; Zhu, Pinwen
A method for performing simultaneous measurements of the electrical resistivity and the Seebeck coefficient at high pressure and high temperature (HPHT) in cubic multi-anvil apparatus is described. For high pressure and high temperature measurements, a four-probe arrangement is used to measure the electrical resistivity and two pairs of chromel-alumel type thermocouples are employed to determine the Seebeck coefficient, respectively. Results of an expected temperature-induced phase transition, pressure-induced metallization and enhancement of the thermoelectric properties were obtained in Ag2Te. This method can provide the necessary data of thermoelectric materials at HPHT. PMID:24517779
The Characteristics of Seebeck Coefficient in Silicon Nanowires Manufactured by CMOS Compatible Process
Silicon nanowires are patterned down to 30 nm using complementary metal-oxide-semiconductor (CMOS) compatible process. The electrical conductivities of n-/p-leg nanowires are extracted with the variation of width. Using this structure, Seebeck coefficients are measured. The obtained maximum Seebeck coefficient values are 122 ?V/K for p-leg and ?94 ?V/K for n-leg. The maximum attainable power factor is 0.74 mW/m K2 at room temperature. PMID:21076666
Measurement system of the Seebeck coefficient or of the electrical resistivity at high temperature
NASA Astrophysics Data System (ADS)
Rouleau, O.; Alleno, E.
A high temperature Seebeck coefficient or electrical resistivity apparatus has been designed and fabricated to measure sample with typical size ś10 ū 1 ū 1 mm3. It can measure both transport properties from 300 K to 1000 K in argon atmosphere. The sample lies transversely on top of two metallic half-cylinders, which contain heating cartridges and allow temperature and thermal gradient control and reversal. The temperature gradient is measured by two type N thermocouples pressed against the upper surface of the sample. The key feature of this apparatus is the disk-shaped junction of each type N thermocouple which strongly improves the thermal contact with the sample. The Seebeck coefficient is obtained by averaging over two measured values with opposite thermal gradient directions (ś▒2 K). For the resistivity measurements, the temperature is stabilized and the temperature gradient is actively reduced below 0.2 K to make negligible any spurious thermal voltage. Uncertainties of ś3% for the Seebeck coefficient and 1% for the resistivity were obtained on Ni samples. The Seebeck coefficient and resistivity have also been measured on a skutterudite sample as small as ś7 ū 1.5 ū 0.5 mm3 with very good agreement with literature.
Cross-plane Seebeck coefficient and thermal conductivity of CuFeSe2 thin film
NASA Astrophysics Data System (ADS)
Lee, P. C.; Ou, M. N.; Luo, J. Y.; Wu, M. K.; Chen, Y. Y.
The CuFeSe2 is a member of the I-III-VI2 semiconductors, whereas it shows different physical properties from the chalcopyrite family, include the tetragonal structure, the small band gap ś0.16 eV and the weak magnetic behavior. Only a few articles focused on this material in recent years. The measurements of the Seebeck coefficient and thermal conductivity of the high quality CuFeSe2 thin film could provide valuable information for its thermal application. In this report, a CuFeSe2 thin film with thickness ś200 nm on SiO2/Si substrate was prepared by pulse laser deposition (PLD). The highly crystallized film shows a preferred orientation (h 0 0) normal to the film surface. Two pairs of heater/sensor Au strips were thermally deposited on the thin film and substrate separately for thermal conductivity measurement using differential 3? method. The Seebeck coefficient across the film plane was directly measured by two additional EMF probes below and above the film with temperature gradient generated by heater/sensor at frequency 2?. The temperature dependence of thermal conductivity and Seebeck coefficient were measured in a wide temperature range from 150 to 300 K. The room-temperature thermal conductivity and Seebeck coefficient are obtained to be 3.5 W/m-K and -108 ?V/K respectively.
Thin Film Thermoelectric Metal-Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity.
Erickson, Kristopher J; Lķonard, Franńois; Stavila, Vitalie; Foster, Michael E; Spataru, Catalin D; Jones, Reese E; Foley, Brian M; Hopkins, Patrick E; Allendorf, Mark D; Talin, A Alec
A new thermoelectric material with high Seebeck coefficient and low thermal conductivity is demonstrated based on an electrically conducting metal-organic framework (MOF) using the guest@MOF concept. This demonstration opens a new avenue for the future development of thermoelectric materials. PMID:25925161
Measurement system of the Seebeck coefficient or of the electrical resistivity at high temperature.
Rouleau, O; Alleno, E
A high temperature Seebeck coefficient or electrical resistivity apparatus has been designed and fabricated to measure sample with typical size ~10 ū 1 ū 1 mm(3). It can measure both transport properties from 300 K to 1000 K in argon atmosphere. The sample lies transversely on top of two metallic half-cylinders, which contain heating cartridges and allow temperature and thermal gradient control and reversal. The temperature gradient is measured by two type N thermocouples pressed against the upper surface of the sample. The key feature of this apparatus is the disk-shaped junction of each type N thermocouple which strongly improves the thermal contact with the sample. The Seebeck coefficient is obtained by averaging over two measured values with opposite thermal gradient directions (~▒2 K). For the resistivity measurements, the temperature is stabilized and the temperature gradient is actively reduced below 0.2 K to make negligible any spurious thermal voltage. Uncertainties of ~3% for the Seebeck coefficient and 1% for the resistivity were obtained on Ni samples. The Seebeck coefficient and resistivity have also been measured on a skutterudite sample as small as ~7 ū 1.5 ū 0.5 mm(3) with very good agreement with literature. PMID:24182159
High temperature Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin disk geometry.
B÷ttger, P H Michael; Flage-Larsen, E; Karlsen, O B; Finstad, Terje G
A versatile apparatus to measure the cross-plane Seebeck coefficient and the resistivity of bulk samples shaped as disks or thin plates, over a temperature range of 300 K-620 K with possible extension to higher temperatures, is presented. It is constructed from readily available equipment and instrumentation with parts that are easily manufactured. The Seebeck coefficient is measured over an average region of the sample under steady-state conditions. The sample resistance is measured using a four-point alternating current method and scaled to room temperature measurements with known geometry to calculate resistivity. A variety of sample shapes are supported. Most importantly, the support of the thin disk geometry allows for the very same samples to be used in a laser flash instrument. The design allows for rough vacuum, high vacuum, or purging with inert gases in the sample chamber. Measurements on thermoelectric ZnSb and a Ni reference material are presented. PMID:22380119
Simultaneous measurement of the Seebeck coefficient and thermal conductivity in the cross-sectional direction of thermoelectric thick film
NASA Astrophysics Data System (ADS)
Jin Kim, Sun; Hyung We, Ju; Soo Kim, Gyung; Jin Cho, Byung
The measurement of the thermoelectric properties of thin film thermoelectric materials has been an issue due to the difficulty and inaccuracy. In this work, we present a new model to simultaneously extract the Seebeck coefficient and thermal conductivity in the cross-sectional direction of thin film thermoelectric material. The proposed method uses a sandwich structure composed of a metal electrode/TE film/metal electrode and measures the external Seebeck coefficient at two different intervals on the metal electrode. A theoretical model enables us to extract the Seebeck coefficient and thermal conductivity of the thermoelectric material from the two external Seebeck coefficient measurement values. The proposed method is applied to screen-printed ZnSb film with copper electrodes and the measurement results were found to lie in a reasonable range. Given that this method is simple to use, it will contribute to the development of thin film thermoelectric devices.
Development of A Seebeck Coefficient Prediction Simulator Using Tight-Binding Quantum Chemical Molecular Dynamics
NASA Astrophysics Data System (ADS)
Tsuboi, Hideyuki; Ogiya, Kei; Chutia, Arunabhiram; Zhu, Zhigang; Lv, Chen; Suzuki, Ai; Sahnoun, Riadh; Koyama, Michihisa; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Del Carpio, Carlos A.; Miyamoto, Akira
Technologies oriented to the development of thermoelectric materials are of great interest because they can assist in directly tapping the vast reserves of currently underused thermal energy. To improve the rational design of high-performance thermoelectric materials, a new numerical procedure for prediction of Seebeck coefficient based on the electronic information from tight-binding quantum chemical molecular dynamics method, has been developed. The newly developed simulator can evaluate Seebeck coefficient theoretically. The simulator is used for the prediction of the Seebeck coefficients for Pt and Si that are the representative materials for metals and semiconductors, respectively. The results show that both coefficients are in quantitative agreement with experimental data, i.e. in the case of Pt metal the predicted value is 5.62 ĄV/K while the experimental is -4.45 ĄV/K. Similarly, in the case of Si semiconductor the predicted value is -324.48 ĄV/K while the experimental is 300-400 ĄV/K. This new developed simulator can be used to guide the rational design of high performance thermoelectric materials.
Simultaneous increase in electrical conductivity and Seebeck coefficient in highly boron-doped nanocrystalline Si.
Neophytou, Neophytos; Zianni, Xanthippi; Kosina, Hans; Frabboni, Stefano; Lorenzi, Bruno; Narducci, Dario
A large thermoelectric power factor in heavily boron-doped p-type nanograined Si with grain sizes ?30Ānm and grain boundary regions of ?2Ānm is reported. The reported power factor is ?5 times higher than in bulk Si. It originates from the surprising observation that for a specific range of carrier concentrations, the electrical conductivity and Seebeck coefficient increase simultaneously. The two essential ingredients for this observation are nanocrystallinity and extremely high boron doping levels. This experimental finding is interpreted within a theoretical model that considers both electron and phonon transport within the semiclassical Boltzmann approach. It is shown that transport takes place through two phases so that high conductivity is achieved in the grains, and high Seebeck coefficient by the grain boundaries. This together with the drastic reduction in the thermal conductivity due to boundary scattering could lead to a significant increase of the figure of merit ZT. This is one of the rare observations of a simultaneous increase in the electrical conductivity and Seebeck coefficient, resulting in enhanced thermoelectric power factor. PMID:23598565
Simultaneous increase in electrical conductivity and Seebeck coefficient in highly boron-doped nanocrystalline Si
NASA Astrophysics Data System (ADS)
Neophytou, Neophytos; Zianni, Xanthippi; Kosina, Hans; Frabboni, Stefano; Lorenzi, Bruno; Narducci, Dario
A large thermoelectric power factor in heavily boron-doped p-type nanograined Si with grain sizes ?30 nm and grain boundary regions of ?2 nm is reported. The reported power factor is ?5 times higher than in bulk Si. It originates from the surprising observation that for a specific range of carrier concentrations, the electrical conductivity and Seebeck coefficient increase simultaneously. The two essential ingredients for this observation are nanocrystallinity and extremely high boron doping levels. This experimental finding is interpreted within a theoretical model that considers both electron and phonon transport within the semiclassical Boltzmann approach. It is shown that transport takes place through two phases so that high conductivity is achieved in the grains, and high Seebeck coefficient by the grain boundaries. This together with the drastic reduction in the thermal conductivity due to boundary scattering could lead to a significant increase of the figure of merit ZT. This is one of the rare observations of a simultaneous increase in the electrical conductivity and Seebeck coefficient, resulting in enhanced thermoelectric power factor.
Uncertainty Analysis of Seebeck Coefficient and Electrical Resistivity Characterization
NASA Technical Reports Server (NTRS)
Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred
In order to provide a complete description of a materials thermoelectric power factor, in addition to the measured nominal value, an uncertainty interval is required. The uncertainty may contain sources of measurement error including systematic bias error and precision error of a statistical nature. The work focuses specifically on the popular ZEM-3 (Ulvac Technologies) measurement system, but the methods apply to any measurement system. The analysis accounts for sources of systematic error including sample preparation tolerance, measurement probe placement, thermocouple cold-finger effect, and measurement parameters; in addition to including uncertainty of a statistical nature. Complete uncertainty analysis of a measurement system allows for more reliable comparison of measurement data between laboratories.
Economical Route to Produce High Seebeck Coefficient Calcium Cobaltate for Bulk Thermoelectric Applications
Selig, Jiri [Lamar University; Lin, Sidney [Lamar University; Lin, Hua-Tay [ORNL; Johnson, D Ray [ORNL; Wang, Hsin [ORNL
Phase pure calcium cobaltate (Ca1.24Co1.62O3.86) was prepared by Self-propagating High-temperature Synthesis (SHS) followed by a short post heat treatment. Prepared powders were characterized by XRD for phase purity, and SEM for particle size and distribution. Temperature histories at the center and on the surface of reaction pellet during the SHS process were monitored and recorded. Particles size of synthesized powders was reduced using a planetary mill to increase its specific surface area. Electrical conductivity, thermal conductivity and Seebeck coefficient of the prepared power were measured and figure of merit was reported.
Round-robin measurements of two candidate materials for a Seebeck coefficient Standard Reference MaterialÖ
NASA Astrophysics Data System (ADS)
Lowhorn, N. D.; Wong-Ng, W.; Zhang, W.; Lu, Z. Q.; Otani, M.; Thomas, E.; Green, M.; Tran, T. N.; Dilley, N.; Ghamaty, S.; Elsner, N.; Hogan, T.; Downey, A. D.; Jie, Q.; Li, Q.; Obara, H.; Sharp, J.; Caylor, C.; Venkatasubramanian, R.; Willigan, R.; Yang, J.; Martin, J.; Nolas, G.; Edwards, B.; Tritt, T.
A Standard Reference Material (SRMÖ) for the Seebeck coefficient is critical for inter-laboratory data comparison and for instrument calibration. To develop this SRMÖ, we have conducted an international round-robin measurement survey of two candidate materialsŚundoped Bi2Te3 and constantan (55% Cu and 45% Ni alloy). Measurements were performed in two rounds by twelve laboratories involved in active thermoelectric research using a number of commercial and custom-built measurement systems and techniques. We report the results of these measurements and the statistical analysis performed. Based on this extensive study, we have selected Bi2Te3 as the prototype standard material.
Laser Synthesis of Nanometric Iron Oxide Films with High Seebeck Coefficient and High Thermoelectric Figure of Merit
NASA Astrophysics Data System (ADS)
Mulenko, S. A.; Gorbachuk, N. T.; Stefan, N.
Radiation of a KrF-laser ( ? = 248 nm) was used for the synthesis by reactive pulsed laser deposition (RPLD) of nanometric iron oxide [Fe2O3-X (0?ū?1)] films with variable thickness, stoichiometry and electrical properties. Film deposition was carried out on <100>Si at its temperature to have being increased from 293 to 800 K. XRD analysis showed that films deposited on Si substrate had polycrystalline structure. Films demonstrated semiconductor temperature trend with variable band gap Eg about 1.0 eV or less depending on oxygen pressure, the number of laser pulses and substrate temperature. Film thickness (13-60 nm) depended on oxygen pressure, substrate temperature and number of laser pulses. The higher substrate temperature, the more crystallinity of the deposited iron oxides' films was resulting in increasing of thermo electromotive force coefficient (Seebeck coefficient, S). It was found out the optimum oxygen pressure in the reactor, substrate temperature and film thickness when the S coefficient was high as 12-4 mV/K in the range 240-330 K. The thermoelectric figure of merit (ZT) was high as 1-6 in the range 280-330 K. This makes nanometric Fe2O3-X films, synthesized by UV photons using RPLD method, an exceptionally strong candidate for effective thermo sensors and thermo converters operating at moderate temperature.
Profiling the Local Seebeck Coefficient of InAs-GaAs Quantum Dots Using Scanning Thermoelectric Microscopy
NASA Astrophysics Data System (ADS)
Lin, Yen-Hsiang; Walrath, Jenna; Huang, Simon; Goldman, Rachel
Thermoelectric (TE) devices offer a method of recovering waste heat through solid state conversion of heat to electricity. However, the typical efficiencies of TE devices are 5-10% which constitutes a barrier to wide spread use. There have recently been a number of reports of an increase in the bulk thermopower due to nanostructuring. In addition to our recent report of enhanced thermopower for GaAs embedded with indium nanocrystals, a theoretical study by Mahan and Sofo suggested that the best thermoelectric materials have a delta function density of states. Quantum dots fit ideally into such a picture. To date, the influence of nanostructuring on the electronic LDOS and thermopower has been studied using spatially averaged measurements; a nanoscale investigation of the effects of nanostructures on thermopower has yet to be presented. To investigate the link between dimensionality and TE properties, we are examining structures ranging from QDs to bulk-like layers, comparing SThEM measurements of the local Seebeck coefficient, S, with STS measurements of the local density of states (LDOS). STM, STS, and SThEM performed on InAs quantum dots (QDs) grown on GaAs. SThEM reveals enhanced S-values near the QD edge; STS reveals band-bending at the QD/GaAs interface, suggesting that the S enhancement is due to interfacial charge accumulation.
Intermediate Valence Tuning and Seebeck Coefficient Optimization in Yb-based Low-Temperature Thermoelectric Materials
NASA Astrophysics Data System (ADS)
Lehr, Gloria; Morelli, Donald; Jin, Hyungyu; Heremans, Joseph
Several Yb-based intermediate valence compounds have unique thermoelectric properties at low temperatures. These materials are interesting to study for niche applications such as cryogenic Peltier cooling of infrared sensors on satellites. Elements of different sizes, which form isostructural compounds, are used to form solid solutions creating a chemical pressure (smaller atoms - Sc) or relaxation (larger atoms - La) to alter the volume of the unit cell and thereby manipulate the average Yb valence. Magnetic susceptibility measurements show a strong correlation between the Seebeck coefficient and the ratio of trivalent to divalent Yb in these compounds. Two different Yb-based solid solution systems, Yb1-xScxAl2 and Yb1-xLaxCu2Si2, demonstrate that the concentration of Yb can be used to tune both the magnitude of the Seebeck coefficient as well as the temperature at which its absolute maximum occurs. This work is supported by Michigan State University and AFOSR-MURI ``Cryogenic Peltier Cooling'' Contract #FA9550-10-1-0533.
Large Closed-Circuit Seebeck Current in Quaternary (Ti,Zr)NiSn Heusler Alloys
NASA Astrophysics Data System (ADS)
Wunderlich, Wilfried; Motoyama, Yuichiro; Sugisawa, Yuta; Matsumura, Yoshihiro
In the (Ti x ,Zr y )Ni w Sn z quaternary system with a composition near ( x + y): w: z = 1:1:1 the existence of the half-Heusler (HH) phase has been confirmed, where Ti and Zr occupy one of the three lattice positions substitutionally. The goal of this study is to characterize the thermoelectric (TE) properties of such materials. TE properties were measured at large temperature differences up to ? T = 800 K, exhibiting Seebeck voltages of about ▒50 mV corresponding to Seebeck coefficients above 0.07 mV/K, with the highest value measured for the (Ti0.4Zr0.6)Ni0.9Sn1.1 composition. Fe and Mn doping could not improve these values further. Measurements under closed-circuit conditions showed very high currents of 0.4 mA for specimens at this particular composition. According to the composition, interfaces between full-Heusler and HH phases are responsible for an electron pull-out phenomenon due to the electric field at their interfaces. First-principle calculations of the electronic band structure confirm this explanation for why (TiZr)NiSn and CrNiSn are p-type TEs whereas NbNiSn is an n-type TE. These considerations will be useful in the search for other such systems.
An experimental apparatus for simultaneously measuring Seebeck coefficient and electrical resistivity from 100 K to 600 K.
Guan, Aiqiang; Wang, Hanfu; Jin, Hao; Chu, Weiguo; Guo, Yanjun; Lu, Guiwu
In this paper, we report a fully automated experimental apparatus for measuring Seebeck coefficient and electrical resistivity of a sample simultaneously in a temperature range of 100-600 K. The Seebeck coefficient is measured using a quasi-steady temperature differential method in which two ceramic heaters are employed to alternately heat the sample. The sample holder is designed to reduce temperature disturbance on its base during a measurement cycle. To demonstrate the accuracy and reliability of the experimental setup, we have performed tests on reference materials including constantan and platinum. PMID:23635205
Apparatus for measuring Seebeck coefficient and electrical resistivity of small dimension samples using infrared microscope as temperature sensor.
Jaafar, W M N Wan; Snyder, J E; Min, Gao
An apparatus for measuring the Seebeck coefficient (?) and electrical resistivity (?) was designed to operate under an infrared microscope. A unique feature of this apparatus is its capability of measuring ? and ? of small-dimension (sub-millimeter) samples without the need for microfabrication. An essential part of this apparatus is a four-probe assembly that has one heated probe, which combines the hot probe technique with the Van der Pauw method for "simultaneous" measurements of the Seebeck coefficient and electrical resistivity. The repeatability of the apparatus was investigated over a temperature range of 40 ░C-100 ░C using a nickel plate as a standard reference. The results show that the apparatus has an uncertainty of ▒4.9% for Seebeck coefficient and ▒5.0% for electrical resistivity. The standard deviation of the apparatus against a nickel reference sample is -2.43 ?VK(-1) (-12.5%) for the Seebeck coefficient and -0.4 ?? cm (-4.6%) for the electrical resistivity, respectively. PMID:23742579
Thermal conductivity and Seebeck coefficients of icosahedral boron arsenide films on silicon carbide
NASA Astrophysics Data System (ADS)
Gong, Y.; Zhang, Y.; Dudley, M.; Zhang, Y.; Edgar, J. H.; Heard, P. J.; Kuball, M.
The thermal conductivity of icosahedral boron arsenide (B12As2) films grown on (0001) 6H-SiC substrates by chemical vapor deposition was studied by the 3? technique. The room temperature thermal conductivity decreased from 27.0 to 15.3 W/m K as the growth temperature was decreased from 1450 to 1275 ░C. This is mainly attributed to the differences in the impurity concentration and microstructure, determined from secondary ion mass spectrometry and high resolution transmission electron microscopy, respectively. Callaway's theory was applied to calculate the temperature-dependent thermal conductivity, and the results are in good agreement with the experimental data. Seebeck coefficients were determined as 107 ?V/K and 136 ?V/K for samples grown at 1350 ░C with AsH3/B2H6 flow ratio equals to 1:1 and 3:5, respectively.
Measurement setup for the simultaneous determination of diffusivity and Seebeck coefficient in a multi-anvil apparatus.
Jacobsen, M K; Liu, W; Li, B
In this paper, a high pressure setup is presented for performing simultaneous measurements of Seebeck coefficient and thermal diffusivity in multianvil apparatus for the purpose of enhancing the study of transport phenomena. Procedures for the derivation of Seebeck coefficient and thermal diffusivity/conductivity, as well as their associated sources of errors, are presented in detail, using results obtained on the filled skutterudite, Ce(0.8)Fe(3)CoSb(12,) up to 12 GPa at ambient temperature. Together with recent resistivity and sound velocity measurements in the same apparatus, these developments not only provide the necessary data for a self-consistent and complete characterization of the figure of merit of thermoelectric materials under pressure, but also serve as an important tool for furthering our knowledge of the dynamics and interplay between these transport phenomena. PMID:23020390
Giant thermoelectric Seebeck coefficient of a two-dimensional electron gas in SrTiO3
Hiromichi Ohta; Sungwng Kim; Yoriko Mune; Teruyasu Mizoguchi; Kenji Nomura; Shingo Ohta; Takashi Nomura; Yuki Nakanishi; Yuichi Ikuhara; Masahiro Hirano; Hideo Hosono; Kunihito Koumoto
Enhancement of the Seebeck coefficient (S) without reducing the electrical conductivity (sigma) is essential to realize practical thermoelectric materials exhibiting a dimensionless figure of merit (ZT=S2.sigma.T.kappa-1) exceeding 2, where T is the absolute temperature and kappa is the thermal conductivity. Here, we demonstrate that a high-density two-dimensional electron gas (2DEG) confined within a unit cell layer thickness in SrTiO3 yields
Measurements of the Thermal Conductivity and Seebeck Coefficient of Natural Nanolaminate Materials
NASA Astrophysics Data System (ADS)
Palma, J.; Lofland, S.; Finkel, P.; Hettinger, J.; Seaman, B.; Gupta, S.; Barsoum, M.
We report thermal transport measurements of materials in the general family M_nAX_n-1, where M is an early transition metal, A is an A-group element (mostly IIIA and IVA) and X is C and/or N and n = 1 to 3. We have measured Ti_3AlC_2, Ti_3SiC_2, and materials with Ge substituted for some of the Si. The results of these measurements suggest that materials in the ┬"312┬" family, have a value of thermal conductivity near room temperature of roughly 40W/Km, with the primary mechanism for heat transport attributed to the entropy of free charge carriers. However, as temperature decreases, the phonon contribution and impurity scattering become more important and differences emerge. These differences with be discussed, as well as differences observed in the thermal transport of Ti_4AlN3 and V_2AlC. We also present Seebeck Coefficient measurements on the same materials and discuss the implications of these results.
Thermal conductivity and Seebeck coefficients of icosahedral boron arsenide films on silicon carbide
Gong, Y.; Kuball, M. [H.H. Wills Physics Laboratory, Centre for Device Thermography and Reliability (CDTR), University of Bristol, Bristol BS8 1TL (United Kingdom); Zhang, Y.; Dudley, M. [Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York 11794-2275 (United States); Zhang, Y.; Edgar, J. H. [Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506 (United States); Heard, P. J. [Interface Analysis Centre, University of Bristol, Bristol BS2 8BS (United Kingdom)
The thermal conductivity of icosahedral boron arsenide (B{sub 12}As{sub 2}) films grown on (0001) 6H-SiC substrates by chemical vapor deposition was studied by the 3{omega} technique. The room temperature thermal conductivity decreased from 27.0 to 15.3 W/m K as the growth temperature was decreased from 1450 to 1275 deg. C. This is mainly attributed to the differences in the impurity concentration and microstructure, determined from secondary ion mass spectrometry and high resolution transmission electron microscopy, respectively. Callaway's theory was applied to calculate the temperature-dependent thermal conductivity, and the results are in good agreement with the experimental data. Seebeck coefficients were determined as 107 {mu}V/K and 136 {mu}V/K for samples grown at 1350 deg. C with AsH{sub 3}/B{sub 2}H{sub 6} flow ratio equals to 1:1 and 3:5, respectively.
Vacancy filling effect in thermoelectric NbO.
Music, Denis; Geyer, Richard W; Bliem, Pascal; Hans, Marcus; Primetzhofer, Daniel
Using density functional theory, we have systematically explored the 1a and 1b vacancy filling in NbO (space group Pm-3m) with Nb and N, respectively, to design compounds with large Seebeck coefficients. The most dominating effect was identified for filling of 1b Wyckoff sites with N giving rise to a fivefold increase in the Seebeck coefficient. This may be understood based on the electronic structure. Nb d-nonmetal p hybridization induces quantum confinement and hence enables the enhancement of the Seebeck coefficient. This was validated by measuring the Seebeck coefficient of reactively sputtered thin films. At 800Ā░C these electrically conductive oxynitrides exhibit the Seebeck coefficient of -70ĀĄVĀK(-1), which is the largest absolute value ever reported for these compounds. PMID:25730353
Vacancy filling effect in thermoelectric NbO
NASA Astrophysics Data System (ADS)
Music, Denis; Geyer, Richard W.; Bliem, Pascal; Hans, Marcus; Primetzhofer, Daniel
Using density functional theory, we have systematically explored the 1a and 1b vacancy filling in NbO (space group Pm-3m) with Nb and N, respectively, to design compounds with large Seebeck coefficients. The most dominating effect was identified for filling of 1b Wyckoff sites with N giving rise to a fivefold increase in the Seebeck coefficient. This may be understood based on the electronic structure. Nb dŚnonmetal p hybridization induces quantum confinement and hence enables the enhancement of the Seebeck coefficient. This was validated by measuring the Seebeck coefficient of reactively sputtered thin films. At 800 ░C these electrically conductive oxynitrides exhibit the Seebeck coefficient of ?70 ĄV K?1, which is the largest absolute value ever reported for these compounds.
Spin seebeck effect and thermal colossal magnetoresistance in graphene nanoribbon heterojunction.
Ni, Yun; Yao, Kailun; Fu, Huahua; Gao, Guoying; Zhu, Sicong; Wang, Shuling
Spin caloritronics devices are very important for future development of low-power-consumption technology. We propose a new spin caloritronics device based on zigzag graphene nanoribbon (ZGNR), which is a heterojunction consisting of single-hydrogen-terminated ZGNR (ZGNR-H) and double-hydrogen-terminated ZGNR (ZGNR-H2). We predict that spin-up and spin-down currents flowing in opposite directions can be induced by temperature difference instead of external electrical bias. The thermal spin-up current is considerably large and greatly improved compared with previous work in graphene. Moreover, the thermal colossal magnetoresistance is obtained in our research, which could be used to fabricate highly-efficient spin caloritronics MR devices. PMID:23459307
Spin Seebeck Effect and Thermal Colossal Magnetoresistance in Graphene Nanoribbon Heterojunction
Ni, Yun; Yao, Kailun; Fu, Huahua; Gao, Guoying; Zhu, Sicong; Wang, Shuling
Spin caloritronics devices are very important for future development of low-power-consumption technology. We propose a new spin caloritronics device based on zigzag graphene nanoribbon (ZGNR), which is a heterojunction consisting of single-hydrogen-terminated ZGNR (ZGNR-H) and double-hydrogen-terminated ZGNR (ZGNR-H2). We predict that spin-up and spin-down currents flowing in opposite directions can be induced by temperature difference instead of external electrical bias. The thermal spin-up current is considerably large and greatly improved compared with previous work in graphene. Moreover, the thermal colossal magnetoresistance is obtained in our research, which could be used to fabricate highly-efficient spin caloritronics MR devices. PMID:23459307
Thermal conductivities, electrical resistivities, and Seebeck coefficients of YBa2Cu3O(7-x) superconductors from 80 to 300 K
NASA Astrophysics Data System (ADS)
Yarbrough, D. W.; Williams, R. K.; Shockley, D. R.
Thermal conductivities, electrical resistivities, and Seebeck coefficients of three polycrystalline YBa2Cu3O(7-x) specimens have been measured over the temperature range 80 to 300 K in a longitudinal-heat-flow apparatus. Smoothed values for thermal conductivity, and electrical resistivity have been obtained for temperatures above the superconducting transition temperature of 90 K. The thermal conductivity values decreased as the temperature was increased, a trend which is inconsistent with the results of some other investigators. The thermal conductivities were less than previously published values and it is suggested that these differences are due to radiative heat loss in the published values. This effect is especially important for linear heat flow measurements on low thermal conductivity materials. The electrical and thermal conductivities of the specimens varied with Ba content and this variation was used to separate the thermal conductivity into lattice and electronic components are significant. The phonon component exhibits the expected temperature variation and an analysis indicates that the electron-phonon interaction is unusually strong.
Influence of Doping Concentration and Ambient Temperature on the Cross-Plane Seebeck Coefficient of InGaAs/InAlAs superlattices
, ZT. With this improvement, InGaAs/InAlAs superlattice microcooler become a promising candidate for on in bulk material -- the Seebeck coefficient did not decrease monotonically with doping concentration devices. Intensive studies looking for monolithically grown micro-coolers based on III-V materials
Seebeck and figure of merit enhancement in nanostructured antimony telluride by antisite defect suppression through sulfur doping.
Mehta, Rutvik J; Zhang, Yanliang; Zhu, Hong; Parker, David S; Belley, Matthew; Singh, David J; Ramprasad, Ramamurthy; Borca-Tasciuc, Theodorian; Ramanath, Ganpati
Antimony telluride has a low thermoelectric figure of merit (ZT < ?0.3) because of a low Seebeck coefficient ? arising from high degenerate hole concentrations generated by antimony antisite defects. Here, we mitigate this key problem by suppressing antisite defect formation using subatomic percent sulfur doping. The resultant 10-25% higher ? in bulk nanocrystalline antimony telluride leads to ZT ? 0.95 at 423 K, which is superior to the best non-nanostructured antimony telluride alloys. Density functional theory calculations indicate that sulfur increases the antisite formation activation energy and presage further improvements leading to ZT ? 2 through optimized doping. Our findings are promising for designing novel thermoelectric materials for refrigeration, waste heat recovery, and solar thermal applications. PMID:22891784
Observations of Co4+ in a Higher Spin State and the Increase in the Seebeck Coefficient of Thermoelectric Ca3Co4O9
Klie, Robert F [University of Illinois, Chicago; Qiao, Q. [University of Illinois, Chicago; Paulauskas, T. [University of Illinois, Chicago; Gulec, A. [University of Illinois, Chicago; Rebola, A. [University of Illinois, Chicago; Ogut, Serdar [University of Illinois, Chicago; Prange, Micah P [Vanderbilt University; Idrobo Tapia, Juan C [ORNL; Pantelides, Sokrates T. [Vanderbilt University; Kolesnik, S. [Northern Illinois University; Dabrowski, B. [Argonne National Laboratory (ANL); Ozdemir, M. [University of Alabama, Tuscaloosa; Boyraz, C. [University of Alabama, Tuscaloosa; Mazumdar, Dipanjan [University of Alabama, Tuscaloosa; Gupta, Dr. Arunava [University of Alabama, Tuscaloosa
Ca{sub 3}Co{sub 4}O{sub 9} has a unique structure that leads to exceptionally high thermoelectric transport. Here we report the achievement of a 27% increase in the room-temperature in-plane Seebeck coefficient of Ca{sub 3}Co{sub 4}O{sub 9} thin films. We combine aberration-corrected Z-contrast imaging, atomic-column resolved electron energy-loss spectroscopy, and density-functional calculations to show that the increase is caused by stacking faults with Co4+-ions in a higher spin state compared to that of bulk Ca{sub 3}Co{sub 4}O{sub 9}. The higher Seebeck coefficient makes the Ca{sub 3}Co{sub 4}O{sub 9} system suitable for many high temperature waste-heat-recovery applications.
Observations of Co4+ in a higher spin state and the increase in the Seebeck coefficient of thermoelectric Ca3Co4O9.
Klie, R F; Qiao, Q; Paulauskas, T; Gulec, A; Rebola, A; ų?³t, S; Prange, M P; Idrobo, J C; Pantelides, S T; Kolesnik, S; Dabrowski, B; Ozdemir, M; Boyraz, C; Mazumdar, D; Gupta, A
Ca3Co4O9 has a unique structure that leads to exceptionally high thermoelectric transport. Here we report the achievement of a 27% increase in the room-temperature in-plane Seebeck coefficient of Ca3Co4O9 thin films. We combine aberration-corrected Z-contrast imaging, atomic-column resolved electron energy-loss spectroscopy, and density-functional calculations to show that the increase is caused by stacking faults with Co4+-ions in a higher spin state compared to that of bulk Ca3Co4O9. The higher Seebeck coefficient makes the Ca3Co4O9 system suitable for many high temperature waste-heat-recovery applications. PMID:23003068
Effect of off-stoichiometry on the transport properties of the Heusler-type Fe2VAl compound
NASA Astrophysics Data System (ADS)
Nishino, Y.; Kato, H.; Kato, M.; Mizutani, U.
We report on the effect of off-stoichiometry on the temperature dependence of electrical resistivity, the Seebeck coefficient, and the Hall coefficient in the Heusler-type Fe2VAl compound. While the stoichiometric Fe2VAl exhibits a semiconductorlike resistivity behavior, a small deviation of the Al content from stoichiometry causes a significant decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient. Substantial enhancements for the Seebeck coefficient are in reasonable accord with changes in the Hall coefficient and can be explained on the basis of the electronic structure, where the Fermi level shifts slightly from the center of a pseudogap due to off stoichiometry.
Thermal conductivity and Seebeck coefficient of 12CaO?7Al2O3 electride with a cage structure
NASA Astrophysics Data System (ADS)
Kim, Sung Wng; Tarumi, Ryuichi; Iwasaki, Hideo; Ohta, Hiromichi; Hirano, Masahiro; Hosono, Hideo
Thermal conductivity (?) and Seebeck coefficient (?) of electron-doped light-metal oxide 12CaO?7Al2O3 (C12A7 electride) with a subnanometer-sized cage structure are reported on single crystals with various electron concentrations (Ne) . The semiconducting C12A7 electride exhibits n -type conduction with the highest ? value of -100?VK-1 at 300 K. The ? exhibits an amorphouslike T2 dependence at low temperatures and varies between 2.3 and 4.5Wm-1K-1 at 300 K. This is an order-of-magnitude lower than that of the constituents, CaO (15Wm-1K-1) and Al2O3 (30Wm-1K-1) . These properties are attributed to the cage structure, suggesting that the semiconducting electride should be regarded as a phonon glass and electron crystal material. The thermoelectric performance of electrides evaluated by a dimensionless figure of merit (ZT) shows an optimized value of 2ū10-3 at 300 K for the semiconducting electride with Ne of 5ū1020cm-3 .
Transport Properties of Bulk Thermoelectrics An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity
Wang, Hsin [ORNL; Porter, Wallace D [ORNL; Bottner, Harold [Fraunhofer-Institute, Freiburg, Germany; Konig, Jan [Fraunhofer-Institute, Freiburg, Germany; Chen, Lidong [Chinese Academy of Sciences; Bai, Shengqiang [Chinese Academy of Sciences; Tritt, Terry M. [Clemson University; Mayolett, Alex [Corning, Inc; Senawiratne, Jayantha [Corning, Inc; Smith, Charlene [Corning, Inc; Harris, Fred [ZT-Plus; Gilbert, Partricia [Marlow Industries, Inc; Sharp, Jeff [Marlow Industries, Inc; Lo, Jason [CANMET - Materials Technology Laboratory, Natural Resources of Canada; Keinke, Holger [University of Waterloo, Canada; Kiss, Laszlo I. [University of Quebec at Chicoutimi
Recent research and development of high temperature thermoelectric materials has demonstrated great potential of converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as an important area for improving energy efficiency. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is Part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main focuses in Part I are on two electronic transport properties: Seebeck coefficient and electrical resistivity.
Transport Properties of Bulk ThermoelectricsŚAn International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity
NASA Astrophysics Data System (ADS)
Wang, Hsin; Porter, Wallace D.; B÷ttner, Harald; K÷nig, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff W.; Lo, Jason; Kleinke, Holger; Kiss, Laszlo
Recent research and development of high-temperature thermoelectric materials has demonstrated great potential for converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air-conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The dimensionless figure of merit, ZT, still needs to be improved from the current value of 1.0 to 1.5 to above 2.0 to be competitive with other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods, and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as a key component for improving energy efficiency. The International Energy Agency (IEA) group under the Implementing Agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main foci in part I are the measurement of two electronic transport properties: Seebeck coefficient and electrical resistivity.
A view of pseudogap formation and the HTSC mechanism from the perspective of Seebeck results on HgBa2CuO4+?
NASA Astrophysics Data System (ADS)
Wilson, J. A.; Farbod, M.
Seebeck data provide invaluable information on HTSC materials over a wide range of doping content. Seebeck thermoelectric results from Hg-1201 have been examined closely with a view to understanding the normal state pseudogap behaviour and the approach to superconductivity. The nature of the generality in the Seebeck data between all HTSC systems is discussed at some length. The pseudogap treatment of such data from Hildebrand et al is expanded to embrace the details developed earlier relating to stripe phase behaviour and a principally electronic negative-U perception of HTSC. The input from recent ARPES and tunnelling results is woven into an appraisal of the pseudogap situation compatible with such a viewpoint. This emphasizes that the role with regard to superconductivity of RVB-based spin coupling above Tc is one of preparing and not pre-pairing. The paper further defines the essential input into cuprate HTSC of the two-dimensionality, the square-planar geometry and the action of the saddle points, the two-subsystem mixed-valent organization and above all the resonant shell-filling-driven negative-U fluctuations.
Application of the Transverse Thermoelectric Effects
H. J. Goldsmid
Most thermoelectric applications make use of the longitudinal Seebeck and Peltier effects. However, it is possible to produce thermoelectric effects in which the electrical and thermal flows are perpendicular to one another. This has certain practical advantages; for example, it makes possible the realization of an infinite-staged cascade refrigerator using a single piece of material. The benefits of separating the
Ratchet effects in graphene and quantum wells with lateral superlattice
Golub, L. E.; Nalitov, A. V.; Ivchenko, E. L. [Ioffe Physical-Technical Institute of the Russian Academy of Sciences, St. Petersburg (Russian Federation); Olbrich, P.; Kamann, J.; Eroms, J.; Weiss, D.; Ganichev, S. D. [Terahertz Center, University of Regensburg, Regensburg (Germany)
Theoretical and experimental studies on the ratchet effects in graphene and in quantum wells with a lateral superlattice excited by alternating electric fields of terahertz frequency range are presented. We discuss the Seebeck ratchet effect and helicity driven photocurrents and show that the photocurrent generation is based on the combined action of a spatially periodic in-plane potential and a spatially modulated light.
Thermoelectric Effect across the Metal-Insulator Domain Walls in VO2
Wu, Junqiao
Thermoelectric Effect across the Metal-Insulator Domain Walls in VO2 Microbeams J. Cao,,, W. Fan-performance thermoelectric materials are currently one of the focuses in materials research for energy conversion technologies.1-4 A good thermoelectric material should have a relatively high thermopower (Seebeck coefficient
Piezoresistive and thermoelectric effects of CNT thin film patterned by EB lithography
Van Thanh Dau; T. Yamada; Dzung Viet Dao; Bui Thanh Tung; K. Hata; S. Sugiyama
The paper reports on characterization of piezoresistive coefficients and Seebeck effect of aligned single wall carbon nanotube (SWNT) forest film. The film was synthesized by water-assisted chemical vapour deposition (CVD), a process known as ┐super growth┐. CNT film was condensed, manually maneuvered and conveniently patterned by EB lithography to form desirable shapes. The piezoresistive coefficient was found to be two
The Seebeck coefficient of iodineĀ
Perez-Fernandez, Domingo Miguel
. Polycrystalline Data 0 (mv/'K) T ('K) QT (mv) 0. 15 302 45. 3 0. 15 296 0. 272 295 80. 2 0. 233 292 68 0. 495 270 133. 7 0. 59 250 147. 5 14 Table 2. Single Crystal Data Q (mv/'K) T ('&) QT (mv) 0. 44 276 115 0. 42 283 118. 9 0. 417 284 118. 4... that region. A simplified version of the above argument is depicted in Figures (B-la) and (B-lb). Figure (B-la) is the case in which all regions have the same mobility. In that case, if the carrier moves to the right (the dot), an amount of a cms...
Application of the Transverse Thermoelectric Effects
H. J. Goldsmid
Most thermoelectric applications make use of the longitudinal Seebeck and Peltier effects. However, it is possible to produce\\u000a thermoelectric effects in which the electrical and thermal flows are perpendicular to one another. This has certain practical\\u000a advantages; for example, it makes possible the realization of an infinite-staged cascade refrigerator using a single piece\\u000a of material. The benefits of separating the
Analysis of Residual Acceleration Effects on Transport and Segregation During Directional Solidification of Tin-Bismuth in the MEPHISTO Furnace Facility
NASA Technical Reports Server (NTRS)
Alexander J. Iwan D. (Principal Investigator)
The objective of this work is to approach the problem of determining the transport conditions (and effects of residual acceleration) during the plane-front directional solidification of a tin-bismuth alloy under low gravity conditions. The work involves using a combination of 2- and 3-D numerical models, scaling analyses, ID models and the results of ground-based and low-gravity experiments. The latter are to be conducted during the MEPHISTO experiment scheduled for USMP-3 in early 1996. The models will be used to predict the response of the transport conditions and consequent solute segregation in directionally solidifying tin-bismuth melt. Real-time Seebeck voltage variations across a Sn-Bi melt during directional solidification in MEPHISTO on USMP-1 show a distinct variation which can be correlated with thruster firings. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-solid interface. This allows a direct comparison of numerical simulations with the Seebeck signals obtained on USMP-1. The effects of such accelerations on composition for a directionally solidifying Sn-Bi alloy have been simulated numerically. USMP-1 acceleration data was used to assist in our choice of acceleration magnitude and orientation. The results show good agreement with experimental observations. The USMP-3 experiments took place earlier this year (February 22 through March 6). There were several differences between the USMP-3 experiments as compared to USMP-1. Firstly a more concentrated alloy was solidified and, secondly, Primary Reaction Control System thruster burns were requested at particular times during four separate growth runs. This allowed us to monitor the response Seebeck response under well-characterized growth conditions. In addition, we carried out simulations during the experiment in order to interpret the Seebeck signal. Preliminary results are described here.
Effects of yttrium doping on the thermoelectric properties of Hf0.6Zr0.4NiSn0.98Sb0.02 half-Heusler alloys
NASA Astrophysics Data System (ADS)
Zhu, T. J.; Xiao, K.; Yu, C.; Shen, J. J.; Yang, S. H.; Zhou, A. J.; Zhao, X. B.; He, J.
The (Y,Sb) codoped (Hf0.6Zr0.4)1-xYxNiSn0.98Sb0.02 (x=0, 0.01, 0.015, 0.02, and 0.025) half-Heusler alloys were prepared by levitation melting and spark plasma sintering. The effects of Y doping on the electrical conductivity, the Seebeck coefficient, and the thermal conductivity have been investigated in the temperature range of 300-900 K. It was found that the Y doping decreased the carrier concentration and electrical conductivity due to the introduction of hole carriers. The thermal conductivity was also reduced upon Y doping, mainly due to the reduced carrier thermal conductivity. The Y-doping substantially increased the Seebeck coefficient because of the decrease in carrier concentration. Pisarenko plot showed that the measured room temperature Seebeck coefficients agrees well with the predicted single parabolic band behavior as a function of the carrier concentration, suggesting that no additional mechanisms cause the extra enhancement of Seebeck coefficient in the Y-Sb codoped half-Heusler alloys. The figure of merit ZT of 1% Y-doped sample was increased by a factor of about 25% than that of the undoped sample.
Doping effects on thermoelectric properties of the off-stoichiometric Heusler compounds Fe{sub 2?x}V{sub 1+x}Al
Nishino, Y., E-mail: firstname.lastname@example.com; Tamada, Y. [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)
The thermoelectric properties of Heusler-type Fe{sub 2?x}V{sub 1+x}Al{sub 1?y}Si{sub y} and Fe{sub 2?x}V{sub 1+x?y}Ti{sub y}Al alloys have been investigated to clarify which off-stoichiometric alloy, i.e., V-rich (x?>?0) or V-poor (x?0), is more effective in enhancing the Seebeck coefficient when doped by Si and Ti, while retaining a low electrical resistivity. Large Seebeck coefficients of ?182??V/K and 110??V/K at 300?K are obtained for n-type Fe{sub 1.95}V{sub 1.05}Al{sub 0.97}Si{sub 0.03} and p-type Fe{sub 2.04}V{sub 0.93}Ti{sub 0.03}Al, respectively. When the Seebeck coefficient is plotted as a function of valence electron concentration (VEC), the VEC dependence for the doped off-stoichiometric alloys falls on characteristic curves depending on the off-stoichiometric composition x. It is concluded that a larger Seebeck coefficient with a negative sign can be obtained for the V-rich alloys rather than the V-poor alloys, whilst good p-type materials are always derived from the V-poor alloys. Substantial enhancements in the Seebeck coefficient for the off-stoichiometric alloys could be achieved by a favorable modification in the electronic structure around the Fermi level through the antisite V or Fe defect formation.
Evaluation of Temperature-Dependent Effective Material Properties and Performance of a Thermoelectric Module
NASA Astrophysics Data System (ADS)
Chien, Heng-Chieh; Chu, En-Ting; Hsieh, Huey-Lin; Huang, Jing-Yi; Wu, Sheng-Tsai; Dai, Ming-Ji; Liu, Chun-Kai; Yao, Da-Jeng
We devised a novel method to evaluate the temperature-dependent effective properties of a thermoelectric module (TEM): Seebeck coefficient ( S m), internal electrical resistance ( R m), and thermal conductance ( K m). After calculation, the effective properties of the module are converted to the average material properties of a p- n thermoelectric pillar pair inside the module: Seebeck coefficient ( S TE), electrical resistivity ( ? TE), and thermal conductivity ( k TE). For a commercial thermoelectric module (Altec 1091) chosen to verify the novel method, the measured S TE has a maximum value at bath temperature of 110░C; ? TE shows a positive linear trend dependent on the bath temperature, and k TE increases slightly with increasing bath temperature. The results show the method to have satisfactory measurement performance in terms of practicability and reliability; the data for tests near 23░C agree with published values.
Thermoelectric effects in graphene nanostructures.
Dollfus, Philippe; Hung Nguyen, Viet; Saint-Martin, Jķr¶me
The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics. PMID:25779989
Effective material properties of thermoelectric composites with elliptical fibers
NASA Astrophysics Data System (ADS)
Wang, Yi-Ze
In the present work, the effective material properties of thermoelectric composites with elliptical fibers are studied. Explicit solutions are derived by the conformal mapping function and Mori-Tanaka method. Numerical simulations are performed to present the behaviors of normalized effective material constants. From the results, it can be observed that both the effective electric and thermal conductivities can be reduced by increasing the filling ratio and a/ b. Such influences can also be found for the effective thermoelectric figure of merit. But they are different from those on the effective Seebeck and Peltier coefficients.
Effect of Ag or Sb addition on the thermoelectric properties of PbTe
NASA Astrophysics Data System (ADS)
Dow, H. S.; Oh, M. W.; Kim, B. S.; Park, S. D.; Min, B. K.; Lee, H. W.; Wee, D. M.
In this study, the effect of Ag or Sb addition on the thermoelectric properties of PbTe including the Seebeck coefficient, the electrical resistivity, and the thermal conductivity, was studied in the temperature range from 323 to 723 K. The major carriers in the Ag-doped and the Sb-doped PbTe are holes and electrons, respectively. A degenerate semiconductor behavior in the electrical transport properties was observed in the Ag-doped, whereas the semi-metallic in the Sb-doped. It was suggested from the results of the Hall effect measurement and the Seebeck coefficient that the effective mass was significantly altered by the Sb-doping. The maximum dimensionless figure of merit, ZT, of Pb1-xAgxTe and Pb1-xSbxTe (x=0.1) alloys showed 0.27 and 0.62 at 723 K, respectively. Based on the analysis of the Seebeck coefficient of the Ag or the Sb-doped PbTe, the interaction between Ag and Sb in PbTe, as expected in the AgPbmSbTem+2 (LAST-m), may be supposed.
Chemical pressure effect on the transport and electronic band structure of Fe2V1-xNbxAl
NASA Astrophysics Data System (ADS)
Lue, C. S.; Liu, R. F.; Song, M. Y.; Wu, K. K.; Kuo, Y. K.
We report the effects of partial substitution of Nb onto the V sites of Fe2VAl by measuring the electrical resistivity, Seebeck coefficient, and thermal conductivity as a function of temperature. It is found that the Nb substitution effectively produces a negative chemical pressure in the system. As a result, the Nb-substituted materials show enhanced semiconductinglike behavior in their electrical resistivity. In addition, the Seebeck coefficient changes sign from positive to negative while replacing V with Nb. These phenomena have been associated with the change of the band features, mainly due to the decrease in the number of the hole carriers. To identify this scenario, we performed ab initio calculations to investigate the electronic band structures of Fe2V1-xNbxAl , focusing on the band variation around the Fermi level. Theoretical results indicate a significant reduction in the hole pockets through Nb substitution, which is consistent with experimental observations.
Transverse laser induced thermoelectric voltage effect in tilted La 0.5Sr 0.5CoO 3 thin films
Y. Wang; L. Yu; P. X. Zhang
The transverse laser induced thermoelectric voltage effect has been investigated in tilted La0.5Sr0.5CoO3 thin films grown on vicinal cut LaAlO3 (100) substrates when films are irradiated by pulse laser at room temperature. The detected voltage signals are demonstrated to originate from the transverse Seebeck effect as the linear dependence of voltage on tilted angle in the range of small tilted
Anomalous effect of vanadium boride seeding on thermoelectric properties of YB{sub 22}C{sub 2}N
Prytuliak, A.; Maruyama, S. [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Mori, T., E-mail: firstname.lastname@example.com [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan)
Highlights: ? We doped YB{sub 22}C{sub 2}N; the long awaited n-type counterpart to p-type boron carbide. ? VB{sub 2} seeding of YB{sub 22}C{sub 2}N showed striking results. ? Thermal treatment effects led to VB{sub 2} being intrinsically doped. ? Large increase of both Seebeck coefficient and electrical conductivity was obtained. - Abstract: Vanadium boride seeded YB{sub 22}C{sub 2}N were synthesized and the thermoelectric properties investigated. YB{sub 22}C{sub 2}N is representative of the series of rare earth borocarbonitrides which is the potential long awaited n-type counterpart to p-type boron carbide. VB{sub 2} seeded samples of YB{sub 22}C{sub 2}N were prepared using VB{sub 2} directly as an initial additive and V{sub 2}O{sub 3} which also results in formation of vanadium diboride in the final product. The resistivity and Seebeck coefficient of samples were measured in the temperature range of 323 K to 1073 K. A dramatic effect of thermal treatment on the Seebeck coefficient of VB{sub 2} seeded samples was observed, and it is indicated that there is possible partial intrinsic doping of vanadium into YB{sub 22}C{sub 2}N. VB{sub 2} is revealed to be a promising additive to improve the thermoelectric properties of YB{sub 22}C{sub 2}N. An enhancement of more than 220% of the maximum absolute value of the Seebeck coefficient was obtained while the resistivity was also reduced considerably.
Thermoelectric and Seebeck coefficients of granular metals.
Glatz, A.; Beloborodov, I. S.; Materials Science Division; California State Univ.
In this work we present a detailed study and derivation of the thermopower and thermoelectric coefficient of nanogranular metals at large tunneling conductance between the grains, g{sub T} >> 1. An important criterion for the performance of a thermoelectric device is the thermodynamic figure of merit which is derived using the kinetic coefficients of granular metals. All results are valid at intermediate temperatures, E{sub c} >> T/g{sub T} > {delta}, where {delta} is the mean energy-level spacing for a single grain and E{sub c} is its charging energy. We show that the electron-electron interaction leads to an increase in the thermopower with decreasing grain size and discuss our results in light of future generation thermoelectric materials for low-temperature applications. The behavior of the figure of merit depending on system parameters such as grain size, tunneling conductance, and temperature is presented.
Effect of Heavy Element Substitution and Off-Stoichiometric Composition on Thermoelectric Properties of Fe2VAl-Based Heusler Phase
NASA Astrophysics Data System (ADS)
Takeuchi, Tsunehiro; Terazawa, Yuichi; Furuta, Yukihiro; Yamamoto, Akio; Mikami, Masashi
The thermoelectric performance of Fe2VAl-based alloys was improved by using the effects of (a) heavy element substitution and (b) off-stoichiometric (Fe/V ? 2) composition. The former method led to a significant reduction of lattice thermal conductivity, whereas the latter to an evolution of the Seebeck coefficient. As a result of sample preparation, we confirmed that the dimensionless figure of merit with n-type behavior was increased up to 0.25 at 420 K for the sample obtained at the optimized composition of Fe1.98V0.97Ta0.05Al0.9Si0.1. Electronic structure calculations revealed that the increase of the Seebeck coefficient observed for Fe-poor samples was caused by a reduction of the density of states near the chemical potential.
Effective Mass of Thermoelectric Materials with Non-Parabolic Kane Bands
NASA Astrophysics Data System (ADS)
Snyder, G. Jeffrey
Effective mass is a concept commonly used to describe electronic transport in semiconductors using a classical analogy to the kinetic theory of gasses. We describe many important electronic transport parameters explicitly with an electronic band mass including: Density of states, charge carrier concentration, mobility, and in particular for thermoelectrics, the Seebeck coefficient. For systems with known electronic band structures these properties can be calculated leading to subtly different definitions of effective mass. In the free electron or parabolic band model the effective masses are the same and we use the term effective mass interchangably. However the differences between these defintions or uses of effective mass become apparent in non-parabolic band structures where it is desirable to describe the transport in terms of a effective mass that changes with energy (or Fermi Level). For example Kane bands, which become more linear and less parabolic at higher energy, have an increased density of states and therefore higher DOS effective mass than a parabolic band. While it is often assumed that also results in a higher thermopower (Seebeck coefficient), calculations of thermopower and Hall carrier concentration from the Kane model show the thermpower is actually reduced. Examples in thermoelectric materials will be discussed.
Effects of Zr substitution on phase transformation and thermoelectric properties of beta-FeSi2
NASA Astrophysics Data System (ADS)
Ito, Mikio; Nagai, Hiroshi; Tahata, Takashi; Katsuyama, Shigeru; Majima, Kazuhiko
Zr-substituted beta-FeSi2 thermoelectric materials, Fe1-xZrxSi2, were synthesized by mechanical alloying (MA) and subsequent hot pressing, and the effects of Zr substitution on phase transformation and thermoelectric properties were investigated. The samples with x up to 0.06 were mostly composed of the Zr-doped beta phase with small amounts of the epsilon phase and the ZrSi phase. In the case of the samples with an x value over 0.10, formation of a large amount of the alpha phase was observed in the x-ray diffraction patterns, and the beta phase completely disappeared for the sample with x=0.30. The Seebeck coefficient below 900 K was markedly reduced by Zr substitution. However, Zr substitution was effective for enhancing the Seebeck coefficient above 900 K and for reducing the electrical resistivity over the entire temperature range. The temperature dependence of the Seebeck coefficient and electrical resistivity of the samples with high Zr content showed a metallic behavior, which was well consistent with the formation of a large amount of the metallic alpha phase. Although the thermal conductivity of the sample with high Zr content increased at high temperature range, the influence of Zr substitution was quite small as compared to that on the electrical resistivity. The figure of merit was significantly improved by Zr substitution, indicating that Zr substitution is quite effective for enhancing the thermoelectric performance of the beta-FeSi2. The maximum figure of merit, 3.38 x10-5/K, was obtained for the sample with x=0.24 at 1070 K, which is about 44 times larger than that of the sample without Zr.
Spin-dependent thermoelectric effects in graphene-based spin valves.
Zeng, Minggang; Huang, Wen; Liang, Gengchiau
Using first-principles calculations combined with non-equilibrium Green's function (NEGF), we investigate spin-dependent thermoelectric effects in a spin valve which consists of zigzag graphene nanoribbon (ZGNR) electrodes with different magnetic configurations. We find that electron transport properties in the ZGNR-based spin valve are strongly dependent on the magnetic configurations. As a result, with a temperature bias, thermally-induced currents can be controlled by switching the magnetic configurations, indicating a thermal magnetoresistance (MR) effect. Moreover, based on the linear response assumption, our study shows that the remarkably different Seebeck coefficients in the various magnetic configurations lead to a very large and controllable magneto Seebeck ratio. In addition, we evaluate thermoelectric properties, such as the power factor, electron thermal conductance and figure of merit (ZT), of the ZGNR-based spin valve. Our results indicate that the power factor and the electron thermal conductance are strongly related to the transmission gap and electron-hole symmetry of the transmission spectrum. Moreover, the value of ZT can reach 0.15 at room temperature without considering phonon scattering. In addition, we investigate the thermally-controlled magnetic distributions in the ZGNR-based spin valve and find that the magnetic distribution, especially the local magnetic moment around the Ni atom, is strongly related to the thermal bias. The very large, multi-valued and controllable thermal magnetoresistance and Seebeck effects indicate the strong potential of ZGNR-based spin valves for extremely low-power consuming spin caloritronics applications. The thermally-controlled magnetic moment in the ZGNR-based spin valve indicates its possible applications for information storage. PMID:23151965
Effects of Ni, Pd, and Pt Substitutions on Thermoelectric Properties of CoSi Alloys
NASA Astrophysics Data System (ADS)
Sun, Hui; Lu, Xu; Morelli, Donald T.
Ni-, Pd-, and Pt-substituted CoSi samples have been prepared by an arc melting and annealing procedure. The x-ray diffraction and scanning electron microscopy results show that Ni and Pd are effective n-type dopants for CoSi, while Pt is immiscible with CoSi and forms an impurity phase with a possible chemical formula of PtCoSi2. The thermoelectric properties were measured from 80 K to 300 K. For Ni- and Pd-doped samples, the electrical resistivity and Seebeck coefficient decrease simultaneously due to the increasing carrier concentration. For Pt-substituted samples, the electrical resistivity also decreases. However, this reduction is thought to be not due to an increase in carriers but rather to originate from the effect of the Pt-rich impurity phase at the grain boundaries. The Seebeck coefficient is not affected by 1% Pt substitution; however, further increase of the Pt level also causes a decrease in the Seebeck coefficient. The room-temperature power factor is 63 ?W K-2 cm-1 for pure CoSi and 73 ?W K-2 cm-1 for the Co0.99Pt0.01Si sample. Although the thermal conductivity is reduced for both n-type-doped and Pt-substituted samples around 80 K, the room-temperature values are still close to that of pure CoSi. As a result, ZT of 0.13 is obtained at room temperature for Co0.99Pt0.01Si, an 18% increase compared with CoSi.
Effect of Ti Substitution on Thermoelectric Properties of W-Doped Heusler Fe2VAl Alloy
NASA Astrophysics Data System (ADS)
Mikami, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.
Effects of element substitutions on thermoelectric properties of Heusler Fe2VAl alloys were evaluated. By W substitution at the V site, the thermal conductivity is reduced effectively because of the enhancement of phonon scattering resulting from the introduction of W atoms, which have much greater atomic mass and volume than the constituent elements of Fe2VAl alloy. W substitution is also effective to obtain a large negative Seebeck coefficient and high electrical conductivity through an electron injection effect. To change the conduction type from n-type to p-type, additional Ti substitution at the V site, which reduces the valence electron density, was examined. A positive Seebeck coefficient as high as that of conventional p-type Fe2VAl alloy was obtained using a sufficient amount of Ti substitution. Electrical resistivity was reduced by the hole doping effect of the Ti substitution while maintaining low thermal conductivity. Compared with the conventional solo-Ti-substituted p-type Fe2VAl alloy, the ZT value was improved, reaching 0.13 at 450 K.
Multiorbital effects on thermoelectric properties of strongly correlated materials
NASA Astrophysics Data System (ADS)
Kargarian, Mehdi; Fiete, Gregory A.
The effects of electronic correlations and orbital degeneracy on thermoelectric properties are studied within the context of multiorbital Hubbard models on different lattices. We use dynamical mean field theory with a modified version of iterative perturbation theory as a solver to calculate the self-energy of the models in a wide range of interaction strengths. The Seebeck coefficient, which measures the voltage drop in response to a temperature gradient across the system, shows a nonmonotonic behavior with temperature in the presence of strong correlations. This anomalous behavior is associated with a crossover from a Fermi liquid metal at low temperatures to a bad metal with incoherent excitations at high temperatures, and is qualitatively captured by the Kelvin formula but not quantitatively. We find that for interactions comparable to the bandwidth, the Seebeck coefficient acquires large values at low temperatures. Moreover, for strongly correlated cases, where the interaction is larger than the bandwidth, the figure of merit is enhanced over a wide range of temperatures because of decreasing electronic contributions to the thermal conductivity. We also find that multiorbital systems will typically yield larger thermopower and figure of merit compared to single-orbital models over a temperature range possibly relevant to applications.
Synthesis and Characterization of 1-, 2- and 3-Dimensional Chalcogenide Nanostructures
Jung, Hyunsung
on Seebeck and Peltier effects, thermoelectric materials canof a thermoelectric material, which is defined as Peltierthermoelectric effects of materials can be described by the combination of Seebeck effects and Peltier
Observation of the Spin Peltier Effect for Magnetic Insulators
NASA Astrophysics Data System (ADS)
Flipse, J.; Dejene, F. K.; Wagenaar, D.; Bauer, G. E. W.; Youssef, J. Ben; van Wees, B. J.
We report the observation of the spin Peltier effect (SPE) in the ferrimagnetic insulator yttrium iron garnet (YIG), i.e., a heat current generated by a spin current flowing through a platinum (Pt)|YIG interface. The effect can be explained by the spin transfer torque that transforms the spin current in the Pt into a magnon current in the YIG. Via magnon-phonon interactions the magnetic fluctuations modulate the phonon temperature that is detected by a thermopile close to the interface. By finite-element modeling we verify the reciprocity between the spin Peltier and spin Seebeck effect. The observed strong coupling between thermal magnons and phonons in YIG is attractive for nanoscale cooling techniques.
Observation of the spin Peltier effect for magnetic insulators.
Flipse, J; Dejene, F K; Wagenaar, D; Bauer, G E W; Ben Youssef, J; van Wees, B J
We report the observation of the spin Peltier effect (SPE) in the ferrimagnetic insulator yttrium iron garnet (YIG), i.e., a heat current generated by a spin current flowing through a platinum (Pt)|YIG interface. The effect can be explained by the spin transfer torque that transforms the spin current in the Pt into a magnon current in the YIG. Via magnon-phonon interactions the magnetic fluctuations modulate the phonon temperature that is detected by a thermopile close to the interface. By finite-element modeling we verify the reciprocity between the spin Peltier and spin Seebeck effect. The observed strong coupling between thermal magnons and phonons in YIG is attractive for nanoscale cooling techniques. PMID:25062233
Giant spin-dependent thermoelectric effect in magnetic tunnel junctions.
Lin, Weiwei; Hehn, Michel; Chaput, Laurent; Negulescu, Bķatrice; Andrieu, Stķphane; Montaigne, Franńois; Mangin, Stķphane
Thermoelectric effects in magnetic nanostructures and the so-called spin caloritronics are attracting much interest. Indeed it provides a new way to control and manipulate spin currents, which are key elements of spin-based electronics. Here we report on a giant magnetothermoelectric effect in a magnetic tunnel junction. The thermovoltage in this geometry can reach 1 mV. Moreover a magnetothermovoltage effect could be measured with ratio similar to the tunnel magnetoresistance ratio. The Seebeck coefficient can then be tuned by changing the relative magnetization orientation of the two magnetic layers in the tunnel junction. Therefore, our experiments extend the range of spintronic devices application to thermoelectricity and provide a crucial piece of information for understanding the physics of thermal spin transport. PMID:22434187
Enhancement of the thermoelectric figure of merit in DNA-like systems induced by Fano and Dicke effects.
Fu, Hua-Hua; Gu, Lei; Wu, Dan-Dan; Zhang, Zu-Quan
We report a theoretical study highlighting the thermoelectric properties of biological and synthetic DNA molecules. Based on an effective tight-binding model of duplex DNA and by using the nonequilibrium Green's function technique, the thermal conductance, electrical conductance, Seebeck coefficient and thermoelectric figure of merit in the system are numerically calculated by varying the asymmetries of energies and electronic hoppings in the backbone sites to simulate the environmental complications and fluctuations. We find that due to the multiple transport paths in the DNA molecule, the Fano antiresonance occurs, and enhances the Seebeck coefficient and the figure of merit. When the energy difference is produced in every opposite backbone site, the Dicke effect appears. This effect gives rise to a semiconducting-metallic transition, and enhances the thermoelectric efficiency of the DNA molecule remarkably. Moreover, as the Fano antiresonance point is close to the Dicke resonance one, a giant enhancement in the thermoelectric figure of merit in the DNA molecule has been found. These results provide a scenario to obtain effective routes to enhance the thermoelectric efficiency in the DNA molecules, and suggest perspectives for future experiments intending to control the thermoelectric transport in DNA-like nanodevices. PMID:25826287
Thermal Cycling Effects on the Thermoelectric Properties of n-Type In, Ce based Skutterudite Compounds
Biswas, Krishnendu; Subramanian, Mas A.; Good, Morris S.; Roberts, Kamandi C.; Hendricks, Terry J.
N-type In-filled CoSb3 are known skutterudite compounds that have shown promising thermoelectric (TE) properties resulting in high dimensionless figure of merit values at elevated temperatures. Their use in various waste heat recovery applications will require that they survive and operate after exposure to harsh thermal cycling environments. This research focused on uncovering the thermal cycling effects on thermoelectric properties of n-type In0.2Co4Sb12 and In0.2Ce0.15Co4Sb12 skutterudite compositions as well as quantifying their temperature-dependent structural properties (elastic modulus, shear modulus, and Poisson's ratio). It was observed that the Seebeck coefficient and resistivity increased only slightly in the double-filled In,Ce skutterudite materials upon thermal cycling. In the In-filled skutterudites the Seebeck coefficient remained approximately the same on thermal cycling, while electrical resistivity increased significantly after thermal cycling. Results also show that thermal conductivity marginally decreases in the case of In-filled skutterudites, whereas the reduction is more pronounced in In, Ce-based skutterudite compounds. The possible reason for this kind of reduction can be attributed to grain pinning effects due to formation of nano inclusions. High temperature structural property measurements (i.e., Young's modulus and shear modulus) are also reported and the results show that these structural properties decrease slowly as temperature increases and the compounds are structurally stable after numerous thermal cycles.
Influence of Thallium on the Shubnikov - de Haas effect and Thermoelectric Properties of Sb2Te3 and Bi2Se3
NASA Astrophysics Data System (ADS)
Kulbachinskii, V. A.; Kudryashov, A. A.; Kytin, V. G.
Influence of Tl-doping on the Shubnikov de Haas effect (SdH) at T=4.2 K in magnetic field up to 38 T of p-Sb2-xTlxTe3 (x=0; 0.005; 0.015; 0.05) and n-Bi2-xTlxSe3 (x=0, 0.01; 0.02; 0.04; 0.06) single crystals has been investigated. By increasing the Tl content, the frequency of the SdH effect and hence the extremal cross-sections of the Fermi-surface decreases in both materials. The hole concentration decreases in Sb2-xTlxTe3 due to a donor effect of Tl and the electron concentration decreases in n-Bi2-xTlxSe3 due to an acceptor effect of Tl. Temperature dependence of the Seebeck coefficient S, electrical conductivity ?, thermal conductivity k and the figure of merit ZT single crystals were measured in the temperature range 77 K - 300 K. The values of k and ? decrease due to Tl doping in Sb2-xTlxTe3 and n-Bi2-xTlxSe3 and the Seebeck coefficient S for all compositions increases in the whole temperature range. The figure of merit ZT increases in both materials. The preferential scattering mechanism in Tl-doped samples changes from the acoustic phonon scattering to the ionized impurity scattering.
Thermal Cycling Effects on the Thermoelectric Properties of n-Type In,Ce-Based Skutterudite Compounds
NASA Astrophysics Data System (ADS)
Biswas, Krishnendu; Subramanian, M. A.; Good, Morris S.; Roberts, Kamandi C.; Hendricks, Terry J.
n-Type In-filled CoSb3 is a known skutterudite compound that has shown promising thermoelectric (TE) properties resulting in high dimensionless figure of merit values at elevated temperatures. Use in various waste heat recovery applications will require survival and operation after exposure to harsh thermal cycling environments. This research focused on uncovering the thermal cycling effects on TE properties of n-type In0.2Co4Sb12 and In0.2Ce0.15Co4Sb12 skutterudite compositions as well as quantifying their temperature-dependent structural properties (elastic modulus, shear modulus, and Poisson's ratio). It was observed that the Seebeck coefficient and resistivity increased only slightly in the double-filled In,Ce skutterudite materials upon thermal cycling. In the In-filled skutterudites the Seebeck coefficient remained approximately the same on thermal cycling, while the electrical resistivity increased significantly after thermal cycling. Results also show that the thermal conductivity marginally decreases in the case of In-filled skutterudites, whereas the reduction is more pronounced in In,Ce-based skutterudite compounds. The possible reason for this kind of reduction can be attributed to grain pinning effects due to formation of nanoinclusions. High-temperature structural property measurements (i.e., Young's modulus and shear modulus) are also reported. The results show that these structural properties decrease slowly as temperature increases and that the compounds are structurally stable after numerous (up to 200) thermal cycles.
Quantum interference and structure-dependent orbital-filling effects on the thermoelectric properties of quantum dot molecules.
Chen, Chih-Chieh; Kuo, David M T; Chang, Yia-Chung
The quantum interference and orbital filling effects on the thermoelectric (TE) properties of quantum dot (QD) molecules with high figure of merit are illustrated via the full solution to the Hubbard-Anderson model in the Coulomb blockade regime. It is found that under certain conditions in the triangular QD molecule (TQDM), destructive quantum interference (QI) can occur, which leads to vanishingly small electrical conductance, while the Seebeck coefficient is modified dramatically. When the TQDM is in the charge localization state due to QI, the Seebeck coefficient is seriously suppressed at low temperature, but is highly enhanced at high temperature. Meanwhile, the behavior of the Lorenz number reveals that it is easier to block charge transport via destructive QI than the electron heat transport at high temperatures. The maximum power factor (PF) in the TQDM occurs under full-filling conditions. Nevertheless, low-filling conditions are preferred for getting the maximum PF in serially coupled triple QDs in general. In double QDs, the maximum PF can be achieved either with orbital-depletion or orbital-filling as a result of electron-hole symmetry. Our theoretical work provides a useful guideline for the advancement of the nanoscale TE technology. PMID:26144845
Performance Prediction of Commercial Thermoelectric Cooler Modules using the Effective Material Properties
NASA Astrophysics Data System (ADS)
Lee, HoSung; Attar, Alaa M.; Weera, Sean L.
This work examines the validity of formulating the effective thermoelectric material properties as a way to predict thermoelectric module performance. The three maximum parameters (temperature difference, current, and cooling power) of a thermoelectric cooler were formulated on the basis of the hot junction temperature. Then, the effective material properties (Seebeck coefficient, electrical resistance, and thermal conductivity) were defined in terms of the three maximum parameters that were taken from either a commercial thermoelectric cooler module or the measurements. It is demonstrated that the simple standard equation with the effective material properties predicts well the performance curves of the four selected commercial products. Normalized parameters over the maximum parameters were also formulated to present the characteristics of the thermoelectric coolers along with the normalized charts. The normalized charts would be universal for a given thermoelectric material.
Seebeck nanoantennas for the detection and characterization of infrared radiation.
Briones, Edgar; Cuadrado, Alexander; Briones, Joel; DĒaz de Le¾n, Ram¾n; MartĒnez-Ant¾n, Juan Carlos; McMurtry, Stefan; Hehn, Michel; Montaigne, Franńois; Alda, Javier; Gonzßlez, Francisco Javier
Arrays of metallic thermocouples in the shape of spiral nanoantennas are proposed as infrared detectors, which use the thermoelectric properties of the metallic interfaces to generate electrical DC signals. The responsivity of these types of antennas is evaluated from both theoretical and numerical perspectives pointing out its potential as infrared sensors. Moreover, the same structures can be used to characterize the state of polarization of the optical near fields with a spatial resolution comparable to the wavelength. PMID:25607310
Electric power output optimization in Seebeck generators: Beyond high ZT
NASA Astrophysics Data System (ADS)
Narducci, Dario
The possibility of enhancing the thermoelectric figure of merit ZT by damping the material thermal conductivity (e.g. by quantum confinement) rather than by increasing its power factor has generated a surge of interest toward the use of nanostructures in thermoelectric generators (TEGs). Actually, while ZT is an appropriate performance index when optimizing the rate of heat conversion in the presence of small thermal power inputs, it may turn out to be misleading when used as a general criterion. Under fixed heat flow conditions, the optimization of ZT may actually proceed only by maximizing the power factor, since materials with low ? may be unable to duly dissipate heat. However, also when operating between heat reservoirs at fixed temperature it is shown that the highest electric power a TEG can output may be obtained by increasing ?, not decreasing it. In addition, it will be presented an equation allowing to determine the TE efficiency over temperature ranges where transport parameters are no longer temperature-independent.
Effect of Heat Treatment in Air on Thermoelectric Properties of Polycrystalline Type-I Silicon-Based Clathrate: Ba8Al15Si31
NASA Astrophysics Data System (ADS)
Anno, Hiroaki; Shirataki, Ritsuko
The effect of heat treatment in air on the thermoelectric properties was investigated for polycrystalline Ba8Al15Si31, where the Al content is almost at the maximum in the Ba8Al x Si46- x system, to evaluate the thermal stability in air at high temperatures, which is indispensable for practical use in thermoelectric applications. Samples were prepared by combining arc melting and spark plasma sintering techniques. Heat treatments were performed in air at 873 K for 10 days and 20 days. The Seebeck coefficient, electrical conductivity, and thermal conductivity were measured before and after the heat treatments. The microstructure and chemical composition were also analyzed before and after the heat treatments, using scanning electron microscopy with energy-dispersive x-ray spectroscopy. Although an oxidation layer was formed on the surface by the heat treatment in air, the chemical composition of the interior of Ba8Al15Si31 was found to be stable in air at 873 K for 10 days and 20 days. The Seebeck coefficient, the electrical conductivity, and the thermal conductivity were found to be almost unchanged after the heat treatment, indicating that Ba8Al15Si31 clathrate is promising as a thermoelectric material with high thermal stability for use in air at 873 K.
Effect of Bismuth Nanotubes on the Thermoelectric Properties of BiSb Alloy Nanocomposites
NASA Astrophysics Data System (ADS)
G³ne?, Ekrem; Landschreiber, Bernadette; Hartung, David; Elm, Matthias T.; Rohner, Christian; Klar, Peter J.; Schlecht, Sabine
Bismuth nanotubes have been synthesized and successfully included in Bi1- x Sb x nanoalloys to form composite structures. The nanotubes were synthesized by transformation of a ?-BiI precursor with n-BuLi solution leading to tubular bismuth structures. The Bi1- x Sb x nanoalloys were produced by ball milling. Three series of composite structures were synthesized by including different fractions (0 wt.%, 3 wt.%, 5 wt.%) of nanotubes in nanoalloys of different composition x. Investigation of thermoelectric and structural properties revealed a decrease of the thermal conductivity of up to 40% for the composites in comparison with alloys without nanotube inclusions. This effect can be attributed to enhanced phonon scattering. Seebeck coefficients and electrical conductivities were both slightly enhanced in the composite series with 3 wt.% nanotube inclusions, leading to enhancement of throughout the series compared with the nanoalloy series without nanotube inclusions.
Interface-Located Photothermoelectric Effect of Organic Thermoelectric Materials in Enabling NIR Detection.
Huang, Dazhen; Zou, Ye; Jiao, Fei; Zhang, Fengjiao; Zang, Yaping; Di, Chong-An; Xu, Wei; Zhu, Daoben
Organic photothermoelectric (PTE) materials are promising candidates for various photodetection applications. Herein, we report on poly[Cux(Cu-ett)]:PVDF, which is an excellent polymeric thermoelectric composite, possesses unprecedented PTE properties. The NIR light irradiation on the poly[Cux(Cu-ett)]:PVDF film could induce obvious enhancement in Seebeck coefficient from 52 ▒ 1.5 to 79 ▒ 5.0 ?V/K. By taking advantage of prominent photothermoelectric effect of poly[Cux(Cu-ett)]:PVDF, an unprecedented voltage of 12 mV was obtained. This excellent performance enables its promising applications in electricity generation from solar energy and NIR detection to a wide range of light intensities ranging from 1.7 mW/cm(2) to 17 W/cm(2). PMID:25875974
Effects of interdot hopping and Coulomb blockade on the thermoelectric properties of serially coupled quantum dots
We have theoretically studied the thermoelectric properties of serially coupled quantum dots (SCQDs) embedded in an insulator connected to metallic electrodes. In the framework of Keldysh GreenÆs function technique, the Landauer formula of transmission factor is obtained using the equation of motion method. Based on such analytical expressions of charge and heat currents, we calculate the electrical conductance, Seebeck coefficient, electron thermal conductance, and figure of merit (ZT) of SCQDs in the linear response regime. The effects of interdot hopping and electron Coulomb interactions on ZT are analyzed. We demonstrate that ZT is not a monotonic increasing function of interdot electron hopping strength (tc). We also show that in the absence of phonon thermal conductance, SCQD can reach the Carnot efficiency as tcapproaches zero. PMID:22591807
Giant Nernst Effect in CeCoIn5
R. Bel; K. Behnia; Y. Nakajima; K. Izawa; Y. Matsuda; H. Shishido; R. Settai; Y. Onuki
We present a study of Nernst and Seebeck coefficients of the heavy-fermion superconductor CeCoIn5. Below 18K, concomitant with a field-dependent Seebeck coefficient, a large sublinear Nernst signal emerges with a magnitude drastically exceeding what is expected for a multiband Fermi-liquid metal. In the mixed state, in contrast with all other superconductors studied before, this signal overwhelms the one associated with
Effects of Fe substitution on the transport properties of the superconductor MgB2
NASA Astrophysics Data System (ADS)
Gahtori, Bhasker; Lal, Ratan; Agarwal, S. K.; Kuo, Y. K.; Sivakumar, K. M.; Hsu, J. K.; Lin, J. Y.; Rao, Ashok; Chen, S. K.; MacManus-Driscoll, J. L.
A systematic study has been made on the effect of Fe substitution by means of resistivity, thermal conductivity, and Seebeck coefficient of the Mg1-xFexB2 superconductor involving 0%, 0.3%, 0.6%, 1.2%, and 3.0% Fe content. The superconducting transition has been found to be very sharp (ś0.2K) for a pristine sample and substitution of Fe results in the decrease of TC with the increase in the transition width. Thermal conductivity is found to decrease with Fe content in general, such that the shoulder present in the pristine sample tends to fade away with increasing Fe. An analysis has been made on the normal state resistivity in terms of a two-band model, and of the thermal conductivity in terms of the Wiedemann-Franz law and the lattice thermal conductivity, and the information obtained on the basis of this analysis has been discussed. Besides, the electronic density of states (DOS) near the Fermi level remains nearly unaffected upon Fe substitution, as evidenced by the Seebeck coefficient measurements. When compared with Mn, Fe behaves like a nonmagnetic element with a modest variation in TC and on the other hand, the TC depression is much stronger when compared with other elements like Al, Cu, etc. Therefore, the observed variation in TC for the presently investigated concentrations of Fe is attributed to the specific nature of the given substituent element (Fe) in altering the phonon frequency and/or electron-phonon coupling strength rather than spin-flip scattering or change in DOS or disorder.
Time-resolved thermoelectrical effect in Sm 0.56Sr 0.44MnO 3 perovskite
NASA Astrophysics Data System (ADS)
Kasper, N. V.; Kattwinkel, A.; Hamad, N.; Bõrner, K.; Troyanchuk, I. O.; Khalyavin, D. D.; Dressel, M.; Gmelin, E.; Schmitt, E.
Sm 0.56Sr 0.44MnO 3 CMR-manganite with perovskite structure has been studied using the time-resolved transient thermoelectric effect and heat capacity measurements. It was observed that the Seebeck voltage shows an electron-like behavior in the temperature range 50-300 K except for a narrow interval in the vicinity of the Curie point. The transition into the metallic-like ferromagnetic state is not accompanied by an appreciable anomaly of the heat capacity. It is argued that the electrical conductivity arises by the holes moving in a 2p-band of oxygen as well as by electrons in a 3d-impurity band. Arguments are given in favor of a short-range charge ordering in a wide temperature interval above TC.
Effect of Ti substitution on the thermoelectric properties of (Zr,Hf)NiSn half-Heusler compounds
NASA Astrophysics Data System (ADS)
Sakurada, S.; Shutoh, N.
The effect of Ti substitution on the thermoelectric properties of (Zr,Hf)NiSn half-Heusler compounds was studied. It was found that the substitution of Ti for (Zr,Hf) reduced the thermal conductivity significantly to a low value of 3.0W/mK at room temperature. In addition, a remarkable enhancement of the Seebeck coefficient due to Ti substitution was observed. Furthermore, doping of the Sn sites in (Ti,Zr,Hf)NiSn with Sb led to a reduction in the electrical resistivity and to a corresponding enhancement of the power factor. In Sb-doped (Ti,Zr,Hf)NiSn compounds, the dimensionless figure of merit, ZT, increased with the increase in temperature and reached a high maximum value of 1.5 at 700K.
Transport Magnetic Proximity Effects in Platinum
NASA Astrophysics Data System (ADS)
Huang, Ssu-Yen
Platinum (Pt) metal, being non-magnetic and having a strong spin-orbit coupling interaction, has been central in detecting pure spin current and establishing most of the recent spin-based phenomena. Thus, it is important to ascertain the transport and magnetic characteristics of thin Pt films in contact with a ferromagnet. In this work, we use both electric and thermal means to conclusively show the transport magnetic proximity effects (MPE) of thin Pt film in contact with ferromagnetic insulator YIG. At thicknesses comparable to, and less than, the spin diffusion length, the strong ferromagnetic characteristics in Pt films on YIG are indistinguishable from those of ferromagnetic permalloy on YIG. The MPE occurs at the interface and decreases exponentially away from the interface, concentrating in only a few monolayers. As a result, the pure spin current detected by a thin Pt is tainted with a spin polarized current. The pure spin current phenomena, such as the inverse spin Hall effect and the spin Seebeck effect, have been contaminated with the anomalous Hall effect and the anomalous Nernst effect respectively. These results raise serious questions about the suitability, and the validity, of using Pt in establishing pure spin current phenomena; on the other hand, a much stronger spin-based effect can be induced by the MPE at the interface. This research is in collaboration with X. Fin, Y. P. Chen, J. Wu, and J. Q. Xiao (University of Delaware), T. Y. Chen (Arizona State University) and D. Qu, W. G. Wang, and C. L. Chien (The Johns Hopkins University).
Effects of Mn substitution on the thermoelectric properties of the electron-doped perovskite Sr1-xLaxTiO3
NASA Astrophysics Data System (ADS)
Okuda, T.; Hata, H.; Eto, T.; Nishina, K.; Kuwahara, H.; Nakamura, M.; Kajimoto, R.
We have tried to improve the n-type thermoelectric properties of the electron- doped Perovskite Sr1-xLaxTiO3 by a Mn substitution. The 1 ~ 2 % Mn substitution enhances the Seebeck coefficient (S) and reduces the thermal conductivity (?) by about 50 % at room temperature (RT) without largely increasing the resistivity for the 5 % electron-doped SrTiO3. Consequently, the power factor at RT keeps a large value comparable to that of Bi2Te3 and the dimensionless figure-of-merits at RT increases twofold by the slight Mn substitution. Such a large reduction of ? at RT is perhaps due to the effect of Jahn-Teller active Mn3+ ions, around which dynamical local lattice distortion may occur.
Phonon and magnon heat transport and drag effects
NASA Astrophysics Data System (ADS)
Heremans, Joseph P.
Thermoelectric generators and coolers constitute today's solid-state energy converters. The two goals in thermoelectrics research are to enhance the thermopower while simultaneously maintaining a high electrical conductivity of the same material, and to minimize its lattice thermal conductivity without affecting its electronic properties. Up to now the lattice thermal conductivity has been minimized by using alloy scattering and, more recently, nanostructuring. In the first part of the talk, a new approach to minimize the lattice thermal conductivity is described that affects phonon scattering much more than electron scattering. This can be done by selecting potential thermoelectric materials that have a very high anharmonicity, because this property governs phonon-phonon interaction probability. Several possible types of chemical bonds will be described that exhibit such high anharmonicity, and particular emphasis will be put on solids with highly-polarizable lone-pair electrons, such as the rock salt I-V-VI2 compounds (e.g. NaSbSe2). The second part of the talk will give an introduction to a completely new class of solid-state thermal energy converters based on spin transport. One configuration for such energy converters is based on the recently discovered spin-Seebeck effect (SSE). This quantity is expressed in the same units as the conventional thermopower, and we have recently shown that it can be of the same order of magnitude. The main advantage of SSE converters is that the problem of optimization is now distributed over two different materials, a ferromagnet in which a flux of magnetization is generated by a thermal gradient, and a normal metal where the flux of magnetization is converted into electrical power. The talk will focus on the basic physics behind the spin-Seebeck effect. Recent developments will then be described based on phonon-drag of spin polarized electrons. This mechanism has made it possible to reach magnitudes of SSE that are comparable to the highest values of classical thermopower measured in semiconductors. This work is supported as part of the Revolutionary Materials for Solid State Energy Conversion (RMSSEC), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, by AFOSR MURI ``Cryogenic Peltier Cooling'' Contract #FA9550-10-1-0533and by NSF-CBET-1133589. Department of Mechanical and Aerospace Engineering; and Department of Physics.
Effects of Pd substitution on the thermoelectric and electronic properties of delafossite Cu1-xPdxFeO2 (x=0.01, 0.03 and 0.05)
NASA Astrophysics Data System (ADS)
Ruttanapun, Chesta
Cu(1-x)Pd(x)FeO2 (x=0.01, 0.03 and 005) delafossite was prepared by solid state reactions and was calcined/sintered at 1050 ░C. The effect of Pd2+ substitution for the Cu1+ sites on the thermoelectric and electronic properties of Cu(1-x)Pd(x)FeO2 were investigated. The crystal structure, oxygen decomposition, thermoelectric and electronic properties were characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), Seebeck coefficient, electrical conductivity and thermal conductivity measurements. The characterization showed that Cu(1-x)Pd(x)FeO2 formed a hexagonal delafossite structure with R3-m symmetry. The existence of Pd2+, Cu1+, Cu2+, Fe3+, Fe4+ and O was revealed from the XPS results. Confirmation of Pd2+ substitution for the Cu1+ sites occurred by increasing the c-axis in the lattice parameter with a Pd content. The O content intercalated at the center of the triangular Cu acted as a support to produce Cu2+ ions and was reduced with an increasing Pd content. The mixed valencies of Cu1+/Cu2+ and Cu1+/Pd2+ in the Cu layer changed the electrical conductivity and the Fe3+/Fe4+ mixed valencies in the FeO6 layer caused the Seebeck coefficient to increase. Both the electrical conductivity and Seebeck coefficient for Pd contents of x=0.01 and 0.03 were higher than that of non-doped CuFeO2. The low thermal conductivity of Cu(1-x)Pd(x)FeO2 resulted from the substitution of Pd, which has a large atomic mass, into structure. The Jonker plot indicated that the electronic properties displayed a degenerate density of states and that Cu(1-x)Pd(x)FeO2 was a semiconductor. A high ZT value of 0.055 was obtained for a Pd content of 0.03 at 950 K. The Pd2+ substitution for the Cu1+ sites influenced the thermoelectric and electronic properties of the delafossite Cu(1-x)Pd(x)FeO2 samples.
Measurement of [N] dependence of electron effective mass in GaAsN
NASA Astrophysics Data System (ADS)
Dannecker, Tassilo; Jin, Yu; Buckeridge, John; Uher, Ctirad; Kurdak, Cagliyan; Fahy, Stephen; Goldman, Rachel S.
The electron effective mass of GaAs1-xNx is predicted to be dependent on N-composition, x; however, conflicting results have been observed using cyclotron resonance and thermomagnetic measurements. Using room temperature thermopower and Hall measurements, in conjunction with assumptions of parabolic bands and Fermi-Dirac statistics, we determined the N composition dependence of the electron effective mass of GaAs1-xNx, in comparison with that of GaAs. Measurements of the Seebeck coefficient, S, for N compositions ranging from x=0 to 0.018, reveal a decrease in S with increasing x. The free carrier concentration, [n], for all GaAsN is lower than for GaAs. For GaAs, we extract an effective mass value of 0.052me, slightly lower than the literature value of 0.067m0. For GaAsN, the effective mass apparently is in all cases greater than for GaAs but varies non-monotonically with x, revealing a minimum at x=0.010 and maxima at x=0.004 and 0.018. This non-monotonic dependence of m* on x cannot be explained with a simple band anti-crossing (BAC) model. Interestingly, this data is consistent with the predictions of Lindsay et al, suggesting the presence of resonances between N-related states and the GaAsN conduction band edge.
Spin transport and spin-caloric effects in (Cr,Zn)Te half-metallic nanostructures: Effect of spin disorder at elevated temperatures from first principles
NASA Astrophysics Data System (ADS)
Kovß?ik, Roman; Mavropoulos, Phivos; Bl³gel, Stefan
An important contribution to the thermoelectric and spin-caloric transport properties in magnetic materials at elevated temperatures is the formation of a spin-disordered state due to local moment fluctuations. This effect has not been largely investigated so far. We focus on various magnetic nanostructures of CrTe in the form of thin layers or nanowires embedded in ZnTe matrix, motivated by the miniaturization of spintronics devices and by recent suggestions that magnetic nanostructures can lead to extraordinary thermoelectric effects due to quantum confinement. The electronic structure of the studied systems is calculated within the multiple scattering screened Korringa-Kohn-Rostoker Green function (KKR-GF) framework. The Monte Carlo method is used to simulate the magnetization in the temperature induced spin disorder. The transport properties are evaluated from the transmission probability obtained using the Baranger-Stone approach within the KKR-GF framework. We find qualitative and quantitative changes in the thermoelectric and spin-caloric coefficients when spin disorder is included in the calculation. Furthermore, we show that substitutional impurities in CrTe nanowires could considerably enhance the Seebeck coefficient and the thermoelectric figure of merit.
Photothermoelectric and photovoltaic effects both present in MoS2
Zhang, Youwei; Li, Hui; Wang, Lu; Wang, Haomin; Xie, Xiaomin; Zhang, Shi-Li; Liu, Ran; Qiu, Zhi-Jun
As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice. PMID:25605348
Photothermoelectric and photovoltaic effects both present in MoS2.
Zhang, Youwei; Li, Hui; Wang, Lu; Wang, Haomin; Xie, Xiaomin; Zhang, Shi-Li; Liu, Ran; Qiu, Zhi-Jun
As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice. PMID:25605348
Effects of doping on transport properties in Cu-Bi-Se-based thermoelectric materials.
Hwang, Jae-Yeol; Mun, Hyeon A; Kim, Sang Il; Lee, Ki Moon; Kim, Jungeun; Lee, Kyu Hyoung; Kim, Sung Wng
The thermoelectric properties of Zn-, In-, and I-doped Cu1.7Bi4.7Se8 pavonite homologues were investigated in the temperature range from 300 to 560 K. On the basis of the comprehensive structural analysis using Rietveld refinement of synchrotron radiation diffraction for Cu(x+y)Bi(5-y)Se8 compounds with the inherently disordered crystallographic sites, we demonstrate a doping strategy that provides a simultaneous control for enhanced electronic transport properties by the optimization of carrier concentration and exceptionally low lattice thermal conductivity by the formation of point defects. Substituted Zn or In ions on Cu site was found to be an effective phonon scattering center as well as an electron donor, while doping on Bi site showed a moderate effect for phonon scattering. In addition, we achieved largely enhanced power factor in small amount of In doping on Cu site by increased electrical conductivity and moderately decreased Seebeck coefficient. Coupled with a low lattice thermal conductivity originated from intensified point defect phonon scattering by substituted In ions with host Cu ions, a thermoelectric figure of merit ZT of 0.24 at 560 K for Cu1.6915In0.0085Bi4.7Se8 was achieved, yielding 30% enhancement compared with that of a pristine Cu1.7Bi4.7Se8 at the same temperature. PMID:25402498
Simple experiments with a thermoelectric module
Yaakov Kraftmakher
The Seebeck and Peltier effects are explored with a commercially available thermoelectric module and a data-acquisition system. Five topics are presented: (i) thermoelectric heating and cooling, (ii) the Seebeck coefficient, (iii) efficiency of a thermoelectric generator, (iv) the maximum temperature difference provided by a thermoelectric cooler and (v) the Peltier coefficient and the coefficient of performance. Using a data-acquisition system,
Investigation of transverse Peltier effect on top-seeded melt textureYBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}
He, Z.H.; Ma, Z.G.; Li, Q.Y.; Luo, Y.Y.; Zhang, J.X. [Department of Physic, Zhongshan University, Guangzhou 510275, People`s Republic of (China)] [Department of Physic, Zhongshan University, Guangzhou 510275, People`s Republic of (China); Meng, R.L.; Chu, C.W. [Texas Center for Superconductivity at the University of Houston, Houston, Texas 77204-5932 (United States)] [Texas Center for Superconductivity at the University of Houston, Houston, Texas 77204-5932 (United States)
The transverse Peltier effect is investigated on the top-seeded melt texture superconductor YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO). By restricting the heat absorbing or evolving on one of the sample{close_quote}s surfaces, the Peltier heat flow is converted into a temperature difference for measurement. The temperature difference is found proportional to the current applied, which is in accordance with the prediction of transverse Peltier effect. Based on a simplified model, the difference of the Seebeck coefficients between the {ital ab} plane and the {ital c} axis, {vert_bar}{ital S}{sub {ital ab}}{minus}{ital S}{sub {ital c}}{vert_bar}, is about 35 {mu}V/K. It is in good agreement with that of large single crystal [I. Terasaki, Y. Sato, S. Tajima, S. Miyamoto, and S. Tanaka, Physica C {bold 235-240}, 1413 (1994)]. The transverse Peltier effect is verified. This supports the idea that the off-diagonal thermoelectric effect is responsible for the anomalously high laser-induced transient transverse voltage on the oriented YBCO superconducting thin films. {copyright} {ital 1996 American Institute of Physics.}
Using first principles Destiny Functional Theory methods to model the Seebeck coefficient of bulk silicon
Mehra, Saahil
Thermoelectrics are gaining significant amounts of attention considering their relevance today in the areas of sustainable energy generation and energy efficiency. In this thesis, the thermoelectric properties of bulk ...
Large Seebeck magnetic anisotropy in thin Co films embedded in Cu determined by ab initio investigations
NASA Astrophysics Data System (ADS)
Popescu, Voicu; Kratzer, Peter
The longitudinal thermopower of a Cu/Co/Cu trilayer system exhibits an oscillatory dependence on the thickness of the Co layer, a behavior related to the formation of quantum well states in the minority spin channel. In addition, it is found to be very sensitive to a switching between an in-plane and out-of-plane magnetization. The resulting magnetothermopower (MTP) is therefore much larger than anticipated from the conventional anisotropic magnetoresistance (AMR). Our calculations establish a direct connection between the magnitude of the MTP signal and the asymmetry of the AMR around the Fermi energy. An enhancement of MTP based on this understanding may offer the possibility of implementing an efficient spin read-out thermoelectric device based on a single ferromagnetic layer.
On the interplay between electrical conductivity and Seebeck coefficient in ultra-narrow silicon nanowires
transport theory. We show that changes in the geometrical features of the NWs such as diameter of the scattering mechanisms, and the shape of the DOS(E) function, contrary to current view. Our results indicate significantly affecting S, which can result in power factor improvements. Index terms: thermoelectric
Large Closed-Circuit Seebeck Current in Quaternary (Ti,Zr)NiSn Heusler Alloys
Wilfried Wunderlich; Yuichiro Motoyama; Yuta Sugisawa; Yoshihiro Matsumura
In the (Ti\\u000a x\\u000a ,Zr\\u000a y\\u000a )Ni\\u000a w\\u000a Sn\\u000a z\\u000a quaternary system with a composition near (xĀ+Āy):w:zĀ=Ā1:1:1 the existence of the half-Heusler (HH) phase has been confirmed, where Ti and Zr occupy one of the three lattice\\u000a positions substitutionally. The goal of this study is to characterize the thermoelectric (TE) properties of such materials.\\u000a TE properties were measured at large
Seebeck Enhancement Through Miniband Conduction in IIIV Semiconductor Superlattices at Low Temperatures
structures1,2 and nanocomposites.3Ł5 However, the numerator in ZT, S2 r, the so-called thermoelectric power. Boltzmann transport in the relaxa- tion-time approximation is used to calculate the thermoelectric transport thermoelectric transport properties are also calculated and discussed to fur- ther enhance the thermoelectric
Effect of synthetic conditions on the thermoelectric properties of polythiophene by electrolytic polymerization
NASA Astrophysics Data System (ADS)
Shinohara, Yoshikazu; Hiraishi, Kentaro; Isoda, Yukihiro; Imai, Yoshio; Oikawa, Hidetoshi
Polythiophene films were synthesized by electrolytic polymerization using nitrobenzene as a solvent and tetra-n-butylammonium as an electrolyte. The electrolytic concentration and thiophene concentration were synthetic parameters. We have evaluated the thermoelectric properties of Seebeck coefficient, electrical conductivity and Hall mobility of the films in the in-plane direction. The films showed a tendency that Seebeck coefficient decreased with an increasing electrical conductivity. High electrical conductivity was achieved by both high carrier concentration and high Hall mobility, which are due to high compactness of polymer structure.
Giant Nernst effect in a Kondo lattice close to a quantum critical point
R. Bel; K. Behnia; Y. Nakajima; K. Izawa; Y. Matsuda; H. Shishido; R. Settai; Y. Onuki
We present a study of Nernst and Seebeck coefficients of the heavy-fermion\\u000asuperconductor CeCoIn$_{5}$. Below 18 K, concomitant with a field-dependent\\u000aSeebeck coefficient, a large sub-linear Nernst signal emerges with a magnitude\\u000adrastically exceeding what is expected for a multi-band Fermi-liquid metal. In\\u000athe mixed state, in contrast with all other superconductors studied before,\\u000athis signal overwhelms the one associated
Engineering Nanomaterials towards Energy Harvesting and Virological Applications
Weng, Ding
thermoelectric effect is considered combinatorial as the Peltier-thermoelectric cooler (TEC). Nowadays, lots of companies put PeltierPeltier Effect and the Seebeck Effect have already covered all the information of thermoelectric
Dual Vacancies: An Effective Strategy Realizing Synergistic Optimization of Thermoelectric Property in BiCuSeO.
Li, Zhou; Xiao, Chong; Fan, Shaojuan; Deng, Yu; Zhang, Wenshuai; Ye, Bangjiao; Xie, Yi
Vacancy is a very important class of phonon scattering center to reduce thermal conductivity for the development of high efficient thermoelectric materials. However, conventional monovacancy may also act as an electron or hole acceptor, thereby modifying the electrical transport properties and even worsening the thermoelectric performance. This issue urges us to create new types of vacancies that scatter phonons effectively while not deteriorating the electrical transport. Herein, taking BiCuSeO as an example, we first reported the successful synergistic optimization of electrical and thermal parameters through Bi/Cu dual vacancies. As expected, as compared to its pristine and monovacancy samples, these dual vacancies further increase the phonon scattering, which results in an ultra low thermal conductivity of 0.37 W m(-1) K(-1) at 750 K. Most importantly, the clear-cut evidence in positron annihilation unambiguously confirms the interlayer charge transfer between these Bi/Cu dual vacancies, which results in the significant increase of electrical conductivity with relatively high Seebeck coefficient. As a result, BiCuSeO with Bi/Cu dual vacancies shows a high ZT value of 0.84 at 750 K, which is superior to that of its native sample and monovacancies-dominant counterparts. These findings undoubtedly elucidate a new strategy and direction for rational design of high performance thermoelectric materials. PMID:25927811
Effects of Heavy Element Substitution on Electronic Structure and Lattice Thermal Conductivity of Fe2VAl Thermoelectric Material
NASA Astrophysics Data System (ADS)
Terazawa, Yuichi; Mikami, Masashi; Itoh, Takashi; Takeuchi, Tsunehiro
By using first-principles cluster calculations, we identified that Ta or W substitution for V is useful for decreasing the lattice thermal conductivity of the Fe2VAl Heusler alloy without greatly affecting the electron transport properties. It was clearly confirmed that the Fe2(V1- x Ta x )Al0.95Si0.05 ( x = 0, 0.025, 0.05), Fe2(V0.9- x Ta x Ti0.1)Al ( x = 0, 0.10, 0.20), and Fe2(V0.9-2 x W x Ti0.1+ x )Al ( x = 0, 0.05, 0.10) alloys indeed possessed large Seebeck coefficient regardless of the amounts of substituted elements, while their lattice thermal conductivity was effectively reduced. As a result of partial substitution of Ta for V, we succeeded in increasing the magnitude of the dimensionless figure of merit of the Heusler phase up to 0.2, which is five times as large as the Ta-free compound.
Effect of heat treatment on the electrical and thermoelectric properties of Sb doped Bi2Se3
NASA Astrophysics Data System (ADS)
Ibrahim, E. M. M.; Abdel Hakeem, A. M.; Adam, A. M. M.; Shokr, E. Kh
Polycrystalline samples of (Bi0.95Sb0.05)2Se3 were prepared using the conventional melting technique at 1273 K, followed by annealing at different temperatures (423, 473, 523 and 573 K) for different time intervals (4, 8, 12 and 16 h). The samples were crystallized in a single phase of Bi2Se3 and no other phases or impurities were observed. The electrical and thermoelectric properties were studied by measuring the electrical conductivity and Seebeck coefficient as functions of temperature in the range 100¢400 K. The results exhibited a metal¢n-type semiconductor transition for all samples. The power factor (Pf) was calculated to determine the effect of the annealing treatment on the performance of the prepared material as a thermoelectric power generator. The highest room temperature value of the Pf was 6.9 ?WK?2cm?1 and was recorded for the sample annealed at 573 K for 16 h. The results confirm the feasibility of using the annealing process to improve the performance of thermoelectric materials.
Effect of Sn Doping on the Thermoelectric Properties of n-type Bi2(Te,Se)3 Alloys
NASA Astrophysics Data System (ADS)
Lee, Jae-Uk; Lee, Deuk-Hee; Kwon, Beomjin; Hyun, Dow-Bin; Nahm, Sahn; Baek, Seung-Hyub; Kim, Jin-Sang
In the present work, 0.01-0.05wt.% Sn-doped Bi2(Te0.9Se0.1)3 alloys were prepared by mechanical deformation followed by hot pressing, and their thermoelectric properties were studied. We observed that the Sn element is a very effective dopant as an acceptor to control the carrier concentration in the n-type Bi2(Te0.9Se0.1)3 alloys to optimize their thermoelectric property. The n-type carrier concentration can be controlled from 4.2 ū 1019/cm3 to 2.4 ū 1019/cm3 by 0.05wt.% Sn-doping. While the Seebeck coefficient and the electrical resistivity are both increased with doping, the power factor remains the same. Therefore, we found that the thermoelectric figure-of-merit becomes maximized at 0.75 when the thermal conductivity has a minimum value for the 0.03wt.% Sn-doped sample.
The effect of structural vacancies on the thermoelectric properties of (Cu?Te){sub 1¢x}(Ga?Te?)x
Ye, Zuxin; Young Cho, Jung; Tessema, Misle M. [Optimal Inc., Plymouth Township, MI 48170 (United States); Salvador, James R., E-mail: email@example.com [GM Global R and D, Warren, MI 48090 (United States); Waldo, Richard A. [GM Global R and D, Warren, MI 48090 (United States); Wang, Hsin; Cai, Wei [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)
We have studied the effects of structural vacancies on the thermoelectric properties of the ternary compounds (Cu?Te)1¢x(Ga?Te?)x (x=0.5, 0.55, 0.571, 0.6, 0.625, 0.667 and 0.75), which are solid solutions found in the pseudo-binary phase diagram for Cu?Te and Ga?Te?, and possesses tunable structural vacancy concentrations. This materials system is not suitable due to the cost and scarcity of the constituent elements, but the vacancy behavior is well understood and will provide a valuable test case for other systems more suitable from the standpoint of cost and abundance of raw materials, which also possesses these vacancy features, but whose structural characterization is lacking at this stage. We find that the nominally defect free phase CuGaTe? possess the highest ZT (ZT=S▓T/??, where S is the Seebeck coefficient and ? is the electrical resistivity ? is the thermal conductivity and T is the absolute temperature) which approaches 1 at 840 K and seems to continuously increase above this temperature. This result is due to the unexpectedly low thermal conductivity found for this material at high temperature. The low thermal conductivity was caused by strong Umklapp (thermally resistive scattering processes involving three phonons) phonon scattering. We find that due to the coincidentally strong scattering of carriers by the structural defects that higher concentrations of these features lead to poor electrical transport properties and decreased ZT. - Graphical abstract: Thermal conductivity and zT as a function of temperature for a series of compounds of the type (Cu?Te)1¢x(Ga?Te?)x (x=0.5, 0.55, 0.571, 0.6, 0.625, 0.667 and 0.75). Highlights: Ģ All the samples show p-type semiconducting behavior in the temperature dependence of the Seebeck and Hall coefficients. Ģ The increased carrier concentration and the introduction of vacancies diminish the carrier mobility and power factor. Ģ The low temperature k decreases significantly as the Ga?Te? content increases due to increasing point defects. Ģ The highest ZT ~ 1.0 at 840 K among the samples in this study was found in CuGaTe?, which contains no vacancies.
Modeling and controller design of a nonlinear time-varying thermal device in a microfluidic platform
Marquez, Horacio J.
diagnosis [4]. Custom-made instrumentation was built by the cascade arrangement of thermoelectric modules as heat pumps and the major physical laws behind them are Seebeck effect, Peltier effect and Thomson
Delay-Time and Thermopower Distributions at the Spectrum Edges of a Chaotic Scatterer
Paris-Sud XI, Universitķ de
devices which can be used for harvesting energy (Seebeck effect) or for cooling (Peltier effect) at the nanoscales, it becomes necessary to study thermoelectric conversion in the quantum limit, where mesoscopic
Oxide based thermoelectric materials for large scale power generation
Song, Yang, M. Eng. Massachusetts Institute of Technology
The thermoelectric (TE) devices are based on the Seebeck and Peltier effects, which describe the conversion between temperature gradient and electricity. The effectiveness of the material performance can be described by ...
Effects of Pd substitution on the thermoelectric and electronic properties of delafossite Cu{sub 1?x}Pd{sub x}FeO{sub 2} (x=0.01, 0.03 and 0.05)
Ruttanapun, Chesta, E-mail: email@example.com
Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} (x=0.01, 0.03 and 005) delafossite was prepared by solid state reactions and was calcined/sintered at 1050 ░C. The effect of Pd{sup 2+} substitution for the Cu{sup 1+} sites on the thermoelectric and electronic properties of Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} were investigated. The crystal structure, oxygen decomposition, thermoelectric and electronic properties were characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), Seebeck coefficient, electrical conductivity and thermal conductivity measurements. The characterization showed that Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} formed a hexagonal delafossite structure with R3?m symmetry. The existence of Pd{sup 2+}, Cu{sup 1+}, Cu{sup 2+}, Fe{sup 3+}, Fe{sup 4+} and O was revealed from the XPS results. Confirmation of Pd{sup 2+} substitution for the Cu{sup 1+} sites occurred by increasing the c-axis in the lattice parameter with a Pd content. The O content intercalated at the center of the triangular Cu acted as a support to produce Cu{sup 2+} ions and was reduced with an increasing Pd content. The mixed valencies of Cu{sup 1+}/Cu{sup 2+} and Cu{sup 1+}/Pd{sup 2+} in the Cu layer changed the electrical conductivity and the Fe{sup 3+}/Fe{sup 4+} mixed valencies in the FeO{sub 6} layer caused the Seebeck coefficient to increase. Both the electrical conductivity and Seebeck coefficient for Pd contents of x=0.01 and 0.03 were higher than that of non-doped CuFeO{sub 2}. The low thermal conductivity of Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} resulted from the substitution of Pd, which has a large atomic mass, into structure. The Jonker plot indicated that the electronic properties displayed a degenerate density of states and that Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} was a semiconductor. A high ZT value of 0.055 was obtained for a Pd content of 0.03 at 950 K. The Pd{sup 2+} substitution for the Cu{sup 1+} sites influenced the thermoelectric and electronic properties of the delafossite Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} samples. - Graphical abstract: Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} (x=0.01, 0.03 and 005) delafossite was prepared by solid state reactions. The characterization showed that Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} formed a hexagonal delafossite structure with R3?m symmetry. The existence of Pd{sup 2+}, Cu{sup 1+}, Cu{sup 2+}, Fe{sup 3+}, Fe{sup 4+} and O was revealed from the XPS results. The O content intercalated at the center of the triangular Cu acted as a support to produce Cu{sup 2+} ions and was reduced with an increasing Pd content. The mixed valencies of Cu{sup 1+}/Cu{sup 2+} and Cu{sup 1+}/Pd{sup 2+} in the Cu layer changed the electrical conductivity and the Fe{sup 3+}/Fe{sup 4+} mixed valencies in the FeO{sub 6} layer caused the Seebeck coefficient to increase. Both the electrical conductivity and Seebeck coefficient for Pd contents of x=0.01 and 0.03 were higher than that of non-doped CuFeO{sub 2}. The low thermal conductivity of Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} resulted from the substitution of Pd, which has a large atomic mass, into structure. A high ZT value of 0.055 was obtained for a Pd content of 0.03 at 950 K. The Pd{sup 2+} substitution for the Cu{sup 1+} sites influenced the thermoelectric and electronic properties of the delafossite Cu{sub (1?x)}Pd{sub (x)}FeO{sub 2} samples. - Highlights: Ģ New compound of Cu{sub 1?x}Pd{sub x}FeO{sub 2} (x=0.01, 0.03 and 0.05) forms phase of delafossite. Ģ The compound displays p-type thermoelectric materials. Ģ The Pd-substituted for Cu{sup 1+} sites forms Pd{sup 2+}. Ģ Mixed valencies of Cu{sup +}/Cu{sup 2+}, Cu{sup +}/Pd{sup 2+} and Fe{sup 3+}/Fe{sup 4+} appear in the compound. Ģ Large atomic mass of Pd-substituted causes low thermal conductivity.
Effect of Nano-ZrW2O8 on the Thermoelectric Properties of Bi85Sb15/ZrW2O8 Composites
NASA Astrophysics Data System (ADS)
Zhou, Min; Chen, Zhen; Chu, Xinxin; Li, Laifeng
In this study, Bi85Sb15/ x wt.% ZrW2O8 ( x = 0, 0.1, 0.5, 1) thermoelectric nanocomposites were prepared successfully by ball milling and spark plasma sintering. The effect of ZrW2O8 nanoparticles on the thermoelectric properties of the Bi85Sb15/ZrW2O8 composite was investigated. Thermal conductivity, Seebeck coefficient, and electrical conductivity were measured between 77 K and 300 K. x-Ray diffraction and scanning electron microscopy were adopted for microstructure characterization of the composites. The electrical transport properties are mainly discussed with regard to the microstructures. The results show that nanoinclusions did not grow during sintering. It is found that the thermal conductivity decreases with the addition of a small amount of ZrW2O8 nanoparticles, which serve as additional phonon-scattering centers. The obtained thermal conductivity is 0.5 W/m K for the Bi85Sb15/1 wt.% ZrW2O8 composite at 80 K, which is just half of the value for the Bi85Sb15 matrix. However, the electrical transport properties are degraded with increasing content of ZrW2O8. The calculated ZT is also degraded due to the poor electrical properties.
Large transverse thermoelectric effects in single crystals of the quasi-one-dimensional metal Li0.9Mo6O17
NASA Astrophysics Data System (ADS)
Moshfeghyeganeh, Saeed; Cohn, Joshua; Dos Santos, Carlos A. M.; Neumeier, John J.
We present measurements of transverse thermoelectric (TE) effects in the temperature range 300-500 K for single crystals of the quasi-one-dimensional (q1D) metal Li0.9Mo6O17 (lithium purple bronze). Prior work demonstrates a highly anisotropic Seebeck coefficient (S), with metallic n-type behavior along the q1D chains (crystallographic b axis), p-type semiconductor behavior in the perpendicular, inter-chain direction (c axis), and a difference ?S ~= 200 ? V/K near T = 450 K. Significant transverse TE voltages, induced by applied temperature differences, and Peltier cooling, induced by applied currents, in specimens with body axes misaligned with the b and c axes will be discussed. Work supported by the U.S. Department of Energy Office of Basic Energy Sciences (DE-FG02-12ER46888, Univ. Miami), the National Science Foundation (DMR-0907036, Mont. St. Univ.), and in Lorena by the CNPq (301334/2007-2) and FAPESP (2009/14524-6).
Effect of cobalt antimonide nanoparticles on the thermoelectric properties of filled and unfilled cobalt antimonide skutterudites
NASA Astrophysics Data System (ADS)
Alboni, Paola Nidia
This study explores the possibility of somewhat decoupling the electrical and thermal conduction, thereby being able to limit the thermal conduction while minimizing the effect on the electrical conduction. The approach is using a nanoparticle layer with a slight compositional mismatch as compared to the bulk skutterudite. A hydrothermal nanoparticle-plating technique has been employed to grow a layer of CoSb3 nanoparticles on the surface of skutterudite bulk matrix grains. Skutterudites of various forms were fabricated and studied in order to assess the effect of this nano-plated layer as a viable method in the improvement of thermoelectric properties of CoSb3 nanocomposites. The skutterudite materials studied include Ni doped, rare earth (La, Ce, or Yb) filled, and Yb and Ce double filled skutterudites. The nanoparticles have a typical size of 30-40 nm while the nano-layer can be up to several hundred nm thick. The nanoparticle layer, which is at the grain boundary after hot pressing, provides an extra scattering channel for phonons, in addition to the "rattler" atoms, grain boundary scattering and mass fluctuation mechanisms found within the bulk matrix grain. The electrical resistivity, Seebeck coefficient, thermal conductivity, and Hall coefficient have been investigated as a function of temperature and the weight percentage (%) of nanoparticles and will be reported with respect to their potential as thermoelectric materials. Improvement in the ZT can be seen in the filled skutterudite series, though the mechanisms providing this improvement are not identical. This nano-plating process shows itself to be a viable method that can be used in conjunction with other techniques, such as doping and void filling, to improve the thermoelectric properties of skutterudites.
Are Effective Properties Effective?
Han, Ru; Ingber, Marc S. [Department of Mechanical Engineering, University of New Mexico, NM 87131 (United States); Hsiao, S.-C. [Department of Hydraulic and Ocean Engineering, National Cheng-Kung University No. 1, Ta-Hsueh Road Tainan 701, Taiwan (China)
The effective moduli (effective Young's modulus, effective Poisson's ratio, effective shear modulus, and effective bulk modulus) of dispersed-phase-reinforced composite materials are determined at the mesoscopic level using three-dimensional parallel boundary element simulations. By comparing the mesoscopic BEM results and the macroscopic results based on effective properties, limitations in the effective property approach have been examined.
Solar thermoelectrics for small scale power generation
Amatya, Reja
In the past two decades, there has been a surge in the research of new thermoelectric (TE) materials, driven party by the need for clean and sustainable power generation technology. Utilizing the Seebeck effect, the ...
Tuning the Thermal Properties of Magnetic Tunnel Junctions
Amin, Vivek Pravin
. The strength of this induced voltage can change as a function of the device's magnetization configuration - known as the magneto-Seebeck effect or magnetothermopower - in analogy with the Giant (and Tunnel) Magnetoresistance. This thesis presents a theoretical...
Tailoring the Thermoelectric Behavior of Electrically Conductive Polymer CompositesĀ
Moriarty, Gregory P.
containing an insulating stabilizer, sodium deoxycholate (DOC), the multi-walled carbon nanotube (MWNT)-filled composites showed a 5x increase in the Seebeck coefficient (S). TCPP did not have a distinct effect on the electrical conductivity (?...
Modeling of solar thermal selective surfaces and thermoelectric generators
McEnaney, Kenneth
A thermoelectric generator is a solid-state device that converts a heat flux into electrical power via the Seebeck effect. When a thermoelectric generator is inserted between a solar-absorbing surface and a heat sink, a ...
Field effect controlled ferromagnetism in transition metal doped ZnO
NASA Astrophysics Data System (ADS)
Bellingeri, E.; Pellegrino, L.; Biasotti, M.; Pallecchi, I.; Canu, G.; Gerbi, A.; Vignolo, M.; Siri, A. S.; Marrķ, D.; Rusponi, S.; Lehnert, A.; Nolting, F.
The ability to externally control the properties of magnetic materials would be highly desirable both from fundamental and technological point of views. In this respect, dilute magnetic semiconductor (DMS), in which a fraction of atoms of the nonmagnetic semiconductor host is replaced by magnetic ions, have recently attracted broad interest for their potential application in spintronics. In this work, we focused on transition metal (TM) (Co, Mn and Cu) doped Zinc oxide (ZnO) because room temperature ferromagnetism was both theoretically predicted and experimentally observed. However, the origin of such ferromagnetism, in particular whether it is a signature of a true DMS behaviour (long range magnetic interaction between the doping ions) or it arises from the formation of secondary phases, segregation or clustering is still under debate. Measuring the dependence of the magnetic properties on the carrier concentration can clarify the underlying physics. The samples were characterized by resistivity, Hall effect, magnetoresistance, Seebeck effect, synchrotron X-ray adsorption spectra (XAS) and magnetic dichroism (XMD) while modulating the carrier density by electric field. The insulating-gate field-effect transistor structures are realized in ZnO/Strontium Titanate (SrTiO 3) heterostructures by pulsed laser deposition. These devices offers the capability to modulate the carrier density of a probe accessible (light, AFM tip, ...) channel, by more than 5 orders of magnitude (from ~10 15 to ~10 20 e -/cm 3, estimated by Hall effect measurements under FE). The Co and Mn films measured by DC SQUID magnetometer result ferromagnetic and anomalous Hall effect was observed at low temperature but nor ferromagnetic nor antiferromagnetic signal was detectable in the XMD spectra. Cu doped films are insulating and nonmagnetic. Photo Emission Electron Microscopy (x-PEEM) and magnetic force microscopy (MFM) showed that the sample are homogeneus and no clustering of TM were detected. A large effect of the magnetic ions, strongly dependent on the carrier concentration, was observed on the transport properties and this effect according can be explained by a giant s-d exchange leading to spin splitting of the s-type conduction band. Since the filling of such band can be modified by field effect a electric field control of the spin polarization can be achieved.
Thermoelectric effects in silicene nanoribbons
NASA Astrophysics Data System (ADS)
Zberecki, K.; Wierzbicki, M.; Barna?, J.; Swirkowicz, R.
Transport and thermoelectric coefficients (including also spin thermopower) of silicene nanoribbons with zigzag edges are investigated by ab initio numerical methods. Local spin density of such nanoribbons reveals edge magnetism. As in graphene, one finds antiferromagnetic and ferromagnetic ordering, with spin polarization at one edge antiparallel or parallel to that at the other edge, respectively. Thermoelectric properties, especially the Seebeck coefficient, significantly depend on the electronic band structure and are enhanced when the Fermi level is in the energy gap. However, the thermoelectric efficiency is significantly reduced when the phonon contribution to the heat conductance is included. This phonon contribution has been calculated numerically by two different methods. Transition from antiferromagnetic to ferromagnetic states leads to a large magnetoresistance as well as to a considerable magnetothermopower. Thermoelectric parameters in the antiparallel configuration, when spin polarization in the left part of the nanoribbon is opposite to that in the right part, are also analyzed.
Cross-plane Seebeck coefficient of ErAs:InGaAs/InGaAlAs superlattices Gehong Zenga
Bowers, John
for solid state re- frigeration and power generation devices. The performance of thermoelectric energy American Institute of Physics. DOI: 10.1063/1.2433751 I. INTRODUCTION Thermoelectric materials can be used conversion devices depends on the thermoelectric figure of merit ZT of a material, which is defined as ZT=S2
Nanograin Effects on the Thermoelectric Properties of Poly-Si Nanowires
NASA Astrophysics Data System (ADS)
Neophytou, N.; Zianni, X.; Ferri, M.; Roncaglia, A.; Cerofolini, G. F.; Narducci, D.
In this work we perform a theoretical analysis of the thermoelectric performance of polycrystalline Si nanowires (NWs) by considering both electron and phonon transport. The simulations are calibrated with experimental data from monocrystalline and polycrystalline structures. We show that heavily doped polycrystalline NW structures with grain size below 100 nm might offer an alternative approach to achieve simultaneous thermal conductivity reduction and power factor improvements through improvements in the Seebeck coefficient. We find that deviations from the homogeneity of the channel and/or reduction in the diameter may provide strong reduction in the thermal conductivity. Interestingly, our calculations show that the Seebeck coefficient and consequently the power factor can be improved significantly once the polycrystalline geometry is properly optimized, while avoiding strong reduction in the electrical conductivity. In such a way, ZT values even higher than the ones reported for monocrystalline Si NWs can be achieved.
Effect of Alkyl Ligand Size on Thermoelectric Properties of Gold Nanocrystal Arrays
NASA Astrophysics Data System (ADS)
Chang, William; Russ, Boris; Urban, Jeffrey; Segalman, Rachel
Traditional thermoelectric materials suffer from low efficiencies due to inverse coupling of the Seebeck coefficient and electrical conductivity, which limits the power factor. Decoupling of these two physical properties represents an exciting opportunity, and has previously been demonstrated in molecular junctions. Using molecular junction design principles for guidance, we designed gold nanocrystal arrays with varying alkyl linkers. We demonstrate that the conductivity of these nanocrystal arrays follows a conventional tunneling model, where the length between nanoparticles dictates conductance. Interestingly, the Seebeck coefficients are not explained by single molecule tunneling junction theory. Metal ligand charge transfer theory, in conjunction with optical spectroscopy, is used to explain thin film charge transport. We compare these macroscale thin film transport properties to single molecule electronic transmission measurements reported in previous studies. This result will lend further insight into how molecular junctions and nanocrystal arrays can be integrated for materials with higher power factors.
Temperature Gradient Measurements by Using Thermoelectric Effect in CNTs-Silicone Adhesive Composite
Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Asiri, Abdullah M.; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved
This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1?1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results. PMID:24748375
Micro-thermoelectric cooler: interfacial effects on thermal and electrical transport
Luciana W. da Silva; Massoud Kaviany
The flows of heat and electricity in a column-type micro-thermoelectric cooler are analyzed by modeling the various interfacial resistances. Electron (barrier tunneling) and phonon (diffuse mismatch) boundary resistances at the thermoelectric\\/metal interface, and thermal non-equilibrium between electrons and phonons adjacent to this interface (cooling length), increase the thermal conduction resistance and decrease the Seebeck coefficient of the thermoelectric elements. These
Effects of Se substitution on the thermoelectric performance of n-type Co{sub 4}Sb{sub 11.3}Te{sub 0.7?x}Se{sub x} skutterudites
Duan, Bo [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, No. 122, Luoshi Road, Wuhan 430070 (China)] [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, No. 122, Luoshi Road, Wuhan 430070 (China); Zhai, Pengcheng, E-mail: email@example.com [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, No. 122, Luoshi Road, Wuhan 430070 (China)] [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, No. 122, Luoshi Road, Wuhan 430070 (China); Liu, Lisheng; Zhang, Qingjie [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, No. 122, Luoshi Road, Wuhan 430070 (China)] [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, No. 122, Luoshi Road, Wuhan 430070 (China)
Highlights: ? The simple solid state reaction technique was employed to prepare Co{sub 4}Sb{sub 11.3}Te{sub 0.7?x}Se{sub x} skutterudites. ? The thermal conductivity decreases gradually with the increasing Se content. ? Doping with moderate Se is an effective way to enhance the thermoelectric performance of Co{sub 4}Sb{sub 11.3}Te{sub 0.7?x}Se{sub x}. ? The highest ZT of 1.11 at 800 K is obtained for the Co{sub 4}Sb{sub 11.3}Te{sub 0.58}Se{sub 0.12} sample. -- Abstract: A series of double-substituted Co{sub 4}Sb{sub 11.3}Te{sub 0.7?x}Se{sub x} skutterudites have been fabricated by combining the solid state reaction and the spark plasma sintering method, and the effects of Se substitution on the thermoelectric properties are characterized by measurements of the electrical conductivity, the Seebeck coefficient and the thermal conductivity in the temperature range of 300¢800 K. Doping Se into the Co{sub 4}Sb{sub 11.3}Te{sub 0.7?x}Se{sub x} matrix suppresses the carrier concentration, and the electrical conductivity actually decreases with the Se content. However, moderate Se doping is effective in enhancing the thermoelectric performance of the n-type Co{sub 4}Sb{sub 11.3}Te{sub 0.7?x}Se{sub x}, because of the resulted dramatically decreased thermal conductivity. Analyses indicate that the heightened point-defect scattering induced by Se doping together with the electron¢phonon scattering induced by Te doping is responsible for the reduction of lattice thermal conductivity of these compounds.
Model for Increasing the Power Obtained from a Thermoelectric Generator Module
NASA Astrophysics Data System (ADS)
Huang, Gia-Yeh; Hsu, Cheng-Ting; Yao, Da-Jeng
We have developed a model for finding the most efficient way of increasing the power obtained from a thermoelectric generator (TEG) module with a variety of operating conditions and limitations. The model is based on both thermoelectric principles and thermal resistance circuits, because a TEG converts heat into electricity consistent with these two theories. It is essential to take into account thermal contact resistance when estimating power generation. Thermal contact resistance causes overestimation of the measured temperature difference between the hot and cold sides of a TEG in calculation of the theoretical power generated, i.e. the theoretical power is larger than the experimental power. The ratio of the experimental open-loop voltage to the measured temperature difference, the effective Seebeck coefficient, can be used to estimate the thermal contact resistance in the model. The ratio of the effective Seebeck coefficient to the theoretical Seebeck coefficient, the Seebeck coefficient ratio, represents the contact conditions. From this ratio, a relationship between performance and different variables can be developed. The measured power generated by a TEG module (TMH400302055; Wise Life Technology, Taiwan) is consistent with the result obtained by use of the model; the relative deviation is 10%. Use of this model to evaluate the most efficient means of increasing the generated power reveals that the TEG module generates 0.14 W when the temperature difference is 25░C and the Seebeck coefficient ratio is 0.4. Several methods can be used triple the amount of power generated. For example, increasing the temperature difference to 43░C generates 0.41 W power; improving the Seebeck coefficient ratio to 0.65 increases the power to 0.39 W; simultaneously increasing the temperature difference to 34░C and improving the Seebeck coefficient ratio to 0.5 increases the power to 0.41 W. Choice of the appropriate method depends on the limitations of system, the cost, and the environment.
The Fundamentals of Thermoelectrics A bachelor's laboratory practical
Ludwig-Maximilians-Universitõt, M³nchen
to thermoelectrics 1 2 The thermocouple 4 3 The Peltier device 5 3.1 n- and p-type Peltier elements thermoelectric effects are the Seebeck effect and the Peltier effect, which when combined with the laws and the Peltier effect are the opposite of one another. Since the initial discovery of thermoelectric effects
High temperature experimental characterization of microscale thermoelectric effects
NASA Astrophysics Data System (ADS)
Favaloro, Tela
Thermoelectric devices have been employed for many years as a reliable energy conversion technology for applications ranging from the cooling of sensors or charge coupled devices to the direct conversion of heat into electricity for remote power generation. However, its relatively low conversion efficiency has limited the implementation of thermoelectric materials for large scale cooling and waste heat recovery applications. Recent advances in semiconductor growth technology have enabled the precise and selective engineering of material properties to improve the thermoelectric figure of merit and thus the efficiency of thermoelectric devices. Accurate characterization at the intended operational temperature of novel thermoelectric materials is a crucial component of the optimization process in order to fundamentally understand material behavior and evaluate performance. The objective of this work is to provide the tools necessary to characterize high efficiency bulk and thin-film materials for thermoelectric energy conversion. The techniques developed here are not bound to specific material or devices, but can be generalized to any material system. Thermoreflectance imaging microscopy has proven to be invaluable for device thermometry owing to its high spatial and temporal resolutions. It has been utilized in this work to create two-dimensional temperature profiles of thermoelectric devices during operation used for performance analysis of novel materials, identification of defects, and visualization of high speed transients in a high-temperature imaging thermostat. We report the development of a high temperature imaging thermostat capable of high speed transient thermoelectric characterization. In addition, we present a noninvasive method for thermoreflectance coefficient calibration ideally suited for vacuum and thus high temperature employment. This is the first analysis of the thermoreflectance coefficient of commonly used metals at high-temperatures. High temperature vacuum thermostats are designed and fabricated with optical imaging capability and interchangeable measurement stages for various electrical and thermoelectric characterizations. We demonstrate the simultaneous measurement of in-plane electrical conductivity and Seebeck coefficient of thin-film or bulk thermoelectric materials. Furthermore, we utilize high-speed circuitry to implement the transient Harman technique and directly determine the cross-plane figure of merit of thin film thermoelectric materials at high temperatures. Transient measurements on thin film devices are subject to complications from the growth substrate, non-ideal contacts and other detrimental thermal and electrical effects. A strategy is presented for optimizing device geometry to mitigate the impact of these parasitics. This design enabled us to determine the cross-plane thermoelectric material properties in a single high temperature measurement of a 25mum InGaAs thin film with embedded ErAs (0.2%) nanoparticles using the bipolar transient Harman technique in conjunction with thermoreflectance thermal imaging. This approach eliminates discrepancies and potential device degradation from the multiple measurements necessary to obtain individual material parameters. Finite element method simulations are used to analyze non-uniform current and temperature distributions over the device area and determine the three dimensional current path for accurate extraction of material properties from the thermal images. Results match with independent measurements of thermoelectric material properties for the same material composition, validating this approach. We apply high magnification thermoreflectance imaging to create temperature maps of vanadium dioxide nanobeams and examine electro-thermal energy conversion along the nanobeam length. The metal to insulator transition of strongly correlated materials is subject to strong lattice coupling which brings about the unique one-dimensional alignment of metal-insulator domains along nanobeams. Many studies have investigated the effects of stress o
Detailed Uncertainty Analysis of the ZEM-3 Measurement System
NASA Technical Reports Server (NTRS)
Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred
The measurement of Seebeck coefficient and electrical resistivity are critical to the investigation of all thermoelectric systems. Therefore, it stands that the measurement uncertainty must be well understood to report ZT values which are accurate and trustworthy. A detailed uncertainty analysis of the ZEM-3 measurement system has been performed. The uncertainty analysis calculates error in the electrical resistivity measurement as a result of sample geometry tolerance, probe geometry tolerance, statistical error, and multi-meter uncertainty. The uncertainty on Seebeck coefficient includes probe wire correction factors, statistical error, multi-meter uncertainty, and most importantly the cold-finger effect. The cold-finger effect plagues all potentiometric (four-probe) Seebeck measurement systems, as heat parasitically transfers through thermocouple probes. The effect leads to an asymmetric over-estimation of the Seebeck coefficient. A thermal finite element analysis allows for quantification of the phenomenon, and provides an estimate on the uncertainty of the Seebeck coefficient. The thermoelectric power factor has been found to have an uncertainty of +9-14 at high temperature and 9 near room temperature.
The thermoelectric properties and crystallography of Bi-Sb-Te-Se thin films grown by ion beam sputtering
NASA Astrophysics Data System (ADS)
Noro, H.; Sato, K.; Kagechika, H.
The effects of the substrate temperature on the composition and microstructure of Bi-Sb-Te-Se thin films are discussed and related to the Seebeck coefficient and resistivity. The films were prepared on silica substrates by argon ion beam sputtering. The effect of subsequent heat treatment is also discussed. The composition becomes stoichiometric at the substrate temperature around 500 K at which the Seebeck coefficient has a maximum and the resistivity has a minimum. The Seebeck coefficient changes its sign at the substrate temperature around 340 K. The crystal structure of the films deposited at room temperature is identified as the rock-salt type, and the change of the thermoelectric properties as a function of the substrate temperature can be mainly attributed to the volume fraction of the Bi2Te3 and rock-salt structures. The subsequent heat treatment is effective in improving the power factor of the stoichiometric thin films.
Ballistic thermoelectric transport in structured nanowires
NASA Astrophysics Data System (ADS)
Wang, Biao; Zhou, Jun; Yang, Ronggui; Li, Baowen
Thermoelectric (TE) devices are solid-state energy converters that can be used for power generation through the Seebeck effect and TE cooling through the Peltier effect. Nanostructures give great opportunities to engineer TE energy conversion efficiency. In this work, we investigate TE transport properties in structured nanowires (NWs) in the ballistic transport regime, where the NWs are bent, kinked, stubbed and segmented like a superlattice nanowire using the GreenÆs function method and the Landauer-B³ttiker formula. A large Seebeck coefficient is found when the transmission gap appears due to the quantum interference effect of electrons. The sign of the Seebeck coefficient can be controlled by the geometries of these structured NWs. This finding is helpful for the design of nanoscale TE devices, such as thermocouple, with the same type of material doping rather than those comprised of n-type and p-type materials.
Effect of Cr and Fe Substitution on the Transport Properties of the Nowotny Chimney-Ladder MnSi ? (1.73 < ? < 1.75) Compounds
NASA Astrophysics Data System (ADS)
Ponnambalam, V.; Morelli, Donald T.
Manganese silicides MnSi ? (1.73 < ? < 1.75) have been substituted with substantial amounts of Cr (<25%) and Fe (<30%) at the Mn site to study the resistivity ( ?), Seebeck ( ?) and Hall coefficients, and thermal conductivity of the resulting compositions. Only marginal reduction in ? is observed upon substituting Cr to as much as 25%. Surprisingly, the Seebeck coefficient is positive even after substituting Fe to 20%. The Hall coefficients are positive, and the carrier concentrations seem to be less sensitive to substitution by either Cr or Fe. The promising aspect of this system is the low lattice thermal conductivity, which is approximately 2.5 W/m K at 300 K for most compositions.
Low effective mass and carrier concentration optimization for high performance p-type Mg2(1-x)Li2xSi0.3Sn0.7 solid solutions.
Zhang, Qiang; Cheng, Long; Liu, Wei; Zheng, Yun; Su, Xianli; Chi, Hang; Liu, Huijun; Yan, Yonggao; Tang, Xinfeng; Uher, Ctirad
Mg2Si1-xSnx solid solutions are promising thermoelectric materials for power generation applications in the 500-800 K range. Outstanding n-type forms of these solid solutions have been developed in the past few years with the thermoelectric figure of merit ZT as high as 1.4. Unfortunately, no comparable performance has been achieved so far with p-type forms of the structure. In this work, we use Li doping on Mg sites in an attempt to enhance and control the concentration of hole carriers. We show that Li as well as Ga is a far more effective p-type dopant in comparison to Na or K. With the increasing content of Li, the electrical conductivity rises rapidly on account of a significantly enhanced density of holes. While the Seebeck coefficient decreases concomitantly, the power factor retains robust values supported by a rather high mobility of holes. Theoretical calculations indicate that Mg2Si0.3Sn0.7 intrinsically possesses the almost convergent double valence band structure (the light and heavy band), and Li doping retains a low density of states (DOS) on the top of the valence band, contrary to the Ga doping at the sites of Si/Sn. Low temperature specific heat capacity studies attest to a low DOS effective mass in Li-doped samples and consequently their larger hole mobility. The overall effect is a large power factor of Li-doped solid solutions. Although the thermal conductivity increases as more Li is incorporated in the structure, the enhanced carrier density effectively shifts the onset of intrinsic excitations (bipolar effect) to higher temperatures, and the beneficial role of phonon Umklapp processes as the primary limiting factor to the lattice thermal conductivity is thus extended. The final outcome is the figure of merit ZT ? 0.5 at 750 K for x = 0.07. This represents a 30% improvement in the figure of merit of p-type Mg2Si1-xSnx solid solutions over the literature values. Hence, designing low DOS near Fermi level EF for given carrier pockets can serve as an effective approach to optimize the PF and thus ZT value. PMID:25178356
Thermoelectric properties of Yb-filled CoSb3 skutterudites
NASA Astrophysics Data System (ADS)
Park, Kwan-Ho; Seo, Won-Seon; Shin, Dong-Kil; Kim, Il-Ho
Yb-filled skutterudites Yb z Co4Sb12 (z = 0, 0.1, 0.2, 0.3, 0.4) were prepared by encapsulated melting and hot pressing. The filling effects of Yb on the transport and the thermoelectric properties of the skutterudites were examined. In the case of z ? 0.3, a secondary phase (YbSb2) was formed, indicating that the filling fraction limit of Yb was z = 0.2 - 0.3. The intrinsic CoSb3 had a high positive Seebeck coefficient, but Yb-filled CoSb3 exhibited a negative Seebeck coefficient. In the case of z ? 0.1, the maximum absolute value of the Seebeck coefficient was | -231| ?VK-1, and in the case of z ? 0.2, the absolute value of the Seebeck coefficient increased with increasing temperature. The electrical conductivity increased and the Seebeck coefficient decreased with increasing Yb filling content due to the increased carrier concentration. The thermal conductivity was reduced significantly by Yb filling, mainly due to a decrease in the lattice thermal conductivity. Also, the lattice thermal conductivity decreased with increasing Yb filling content, indicating that the phonon scattering was caused by the rattling of Yb fillers in the voids of the skutterudite structure. Yb0.2Co4Sb12 showed the highest figure of merit of 1.0 at 823 K.
Tuning the Thermal Properties of Magnetic Tunnel JunctionsĀ
Amin, Vivek Pravin
Thermoelectric Effects . . . . . . . . . . . . . . . . . . . . 57 vii 4.2.1 Seebeck Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.2.2 Peltier Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.3 Spin Caloritronics.../TMR) . . . . . . . . . . . 52 3.3 Tunneling Anisotropic Magnetoresistance (TAMR) . . . . . . . . . . 54 4. THERMOELECTRIC PHENOMENON . . . . . . . . . . . . . . . . . . . 56 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.2 Traditional...
Effective Schools and Effective Principals: Effective Research?
ERIC Educational Resources Information Center
Zirkel, Perry A.; Greenwood, Scott C.
This article cautions that prescriptive announcements for school improvement currently in vogue are not all clearly justified by research on school effectiveness. An overview of the strong principal factor is used as an example. (MT)
Thermoelectric effect in nano-scaled lanthanides doped ZnO
NASA Astrophysics Data System (ADS)
Otal, E. H.; Schaeuble, N.; Aguirre, M. H.; Canepa, H. R.; Wals÷e de Reca, N. E.
Start Nano-scaled ZnO with 1% Er doping was prepared by soft chemistry methods. The synthesis was carried out in anhydrous polar solvent to achieve a crystal size of a few nanometers. Resulting particles were processed as precipitates or multi layer films. Structural characterization was evaluated by X-Ray diffraction and transmission and scanning electron microscopy. In the case of films, UV-Vis characterization was made. The thermoelectrical properties of ZnO:Er were evaluated and compared with a typical good thermoelectric material ZnO:Al. Both materials have also shown high Seebeck coefficients and they can be considered as potential compounds for thermoelectric conversion.
Development of thermoelectric materials based on Fe2VAl Heusler compound for energy harvesting applications
NASA Astrophysics Data System (ADS)
Nishino, Y.
The Heusler-type Fe2VAl compound is a nonmagnetic semimetal with a sharp pseudogap at the Fermi level. Doping of quaternary elements causes a large enhancement in the Seebeck coefficient, in parallel with a significant decrease in the electrical resistivity. Since the Seebeck coefficient varies systematically with the valence electron concentration (VEC), irrespective of doping elements, the net effect of doping is most likely to cause a rigid-bandlike shift of the Fermi level from the central region in the pseudogap. Further increase in the Seebeck coefficient can be expected for the off-stoichiometric Fe2-xV1+xAl alloys due to tuning of the Fermi level by doping. The Fe2VAl-based compounds are a promising candidate for thermoelectric power generation near room temperature, because of the possession of higher thermoelectric power factor than that of Bi-Te system.
Thermoelectric Devices: Solid-State Refrigerators and Electrical Generators in the Classroom
Edmund J. Winder; Arthur B. Ellis; George C. Lisensky
Thermoelectric devices are solid-state devices that convert thermal energy from a temperature gradient into electrical energy (the Seebeck effect) or convert electrical energy into a temperature gradient (the Peltier effect). The first application is used most notably in spacecraft power generation systems (for example, in Voyager I and II) and in thermocouples for temperature measurement, while the second application is
PHYSICAL REVIEW B 87, 115147 (2013) Delay-time and thermopower distributions at the spectrum edges of a chaotic scatterer
Muttalib, Khandker
(Seebeck effect) or for cooling (Peltier effect) at the nanoscale, it becomes necessary to study thermoelectric conversion in the quantum limit, where mesoscopic fluctuations become important. To illustrate that the thermoelectric conversion is associated with a large meso- scopic fluctuation and illustrates the necessity
Modeling, control and experimental validation of a novel actuator based on shape memory alloys
Roberto Romano; Eduardo Aoun Tannuri
The paper presents the development of a mechanical actuator using a shape memory alloy with a cooling system based on the thermoelectric effect (Seebeck¢Peltier effect). Such a method has the advantage of reduced weight and requires a simpler control strategy as compared to other forced cooling systems. A complete mathematical model of the actuator was derived, and an experimental prototype
Modern Thermocouple Experiment.
ERIC Educational Resources Information Center
Chang, K. N.; And Others
Describes a thermocouple circuit used to measure Joule heating as well as Peltier heating and cooling for a copper-Constantan metallic junction. Shows how the Seebeck effect from a thermocouple can monitor the temperature condition of a junction with regard to input power and Peltier effect. (Author/GA)
A study of piezoelectric properties of carbon fiber reinforced concrete and plain cement paste during dynamic loading
Mingqing Sun; Qingping Liu; Zhuoqiu Li; Yaozu Hu
Carbon fiber reinforced concrete (CFRC) is an intrinsically smart material, which can be used to realize the self-monitoring of concrete structures based on its piezoresistance effect and the Seebeck effect. An experimental study was made to examine the piezoelectric properties of CFRC and plain cement paste. The results show that both CFRC and plain cement paste exhibit piezoelectric behavior, which
NASA Astrophysics Data System (ADS)
Kinigstein, Steven Michael
In writing Further Effects, I intended to illustrate the benefits that are to be had from the use of effects - processing, when applied at the compositional level, rather than as a post-compositional afterthought. When effects are used creatively in the compositional stage, they will influence the very nature of a piece. They are capable of expressing rhythmic and metric ideas. They can alter the natural timbre of an instrument. This can be done on levels of abstraction ranging from discreet subtlety to disguise beyond recognition. There is one effect (known as "pitch shift.") that allows an instrument to play pitches that are well outside of its range. In Further Effects, I direct the performers to use a volume pedal (which I view as a tool, rather than an effect) for the broadened creative use of dynamics that it so efficiently grants. The use of an effects processor and volume pedal creates a need for ancillary equipment. An amplifier, cables, and an electric hook-up (a microphone or a pickup) will be required for each instrument. While an amplifier serves to project the processed sound, there must also be a device or method to suppress unprocessed sound. A great deal of thought and work goes into the use of effects; yet I feel it is wasteful to use this musical resource merely as post-compositional decoration.
The greenhouse effect refers to the phenomenon whereby carbon dioxide and other small-molecule gases trap longwave infrared radiation (heat) in the atmosphere, thereby warming the Earth. After several years of relatively low priority, the greenhouse effect is re-emerging as a subject of concern to Congress and regulatory agencies. So also is the sister issue of ozone depletion, the breakdown of
ERIC Educational Resources Information Center
Foord, Kathleen A.; Haar, Jean M.
Books by education experts and speakers at national professional conferences have inspired many school leaders to initiate professional learning communities (PLCs). Sustaining them effectively to raise student achievement is another matter. How can one know whether a PLC is moving toward a desired outcome? Measuring effectiveness requires anģ
Fry, R J
Deterministic effects are distinguished from stochastic effects for radiation protection purposes by the following characteristics: both incidence and severity increase as a function of dose after a threshold dose is reached. Cell killing is central to all deterministic effects with the exception of radiation-induced cataracts. The understanding of radiation-induced killing of cells has increased greatly in the last decade with an extraordinarily intense interest in apoptosis. Programmed cell death has long been known to developmental biologists and the importance of cell death has been recognized and quantified by tumor biologists and students of cell kinetics but the coining of a new name and the increase of understanding of the molecular aspects of cell death has stimulated interest. Some cells appear to be very sensitive to radiation and undergo apoptosis, whereas others such as fibroblasts do not with equal frequency. This characteristic, like many others, underlines the genetic differences among cell types. We are reaching a time that there are techniques and the knowledge to apply them to clinical and radiation protection problems. In radiotherapy, success depends on the differential effect between tumor and normal tissues that is obtained. To design the optimum therapy, a profile of both the tumor cells and the cells of the normal tissues that may be at risk would help. The profile would characterize the radiosensitivity and the underlying factors, which could help in the choice of adjunct therapy for tumor and normal tissue. Fibrosis, a common unwanted late effect, appears to be influenced by genetic factors, at least in experimental animals. Techniques are available for treating people as individuals more than ever before, and that must be a good thing to do. Protection against deterministic effects would seem an easy matter but we are uncomfortably ignorant of the precise effect of protracted low-dose irradiation on tissues, such as the bone marrow and the testis, important features of risk in space. Entering the new century, it may be timely to classify radiation effects, as Radiation Effects Research Foundation (RERF) has done, into cancer, genetic effects, and noncancer effects. The recognition in the atomic-bomb survivors of noncancer effects at doses on the order of 0.5 Sv (half the dose level considered a threshold in earlier studies) should stimulate interest in deterministic effects. PMID:11281201
The Effect of Structural Vacancies on the Thermoelectric Properties of (Cu2Te)1-x(Ga2Te3)x
Ye, Zuxin [GM Research and Development Center; Cho, Jung Y [GM R& D and Planning, Warren, Michigan; Tessema, Misle [GM Research and Development Center; Salvador, James R. [GM R& D and Planning, Warren, Michigan; Waldo, Richard [GM R& D and Planning, Warren, Michigan; Wang, Hsin [ORNL; Cai, Wei [ORNL
We have studied the effects of structural vacancies on the thermoelectric properties of the ternary compounds (Cu2Te)1-x(Ga2Te3)x (x = 0.5, 0.55, 0.571, 0.6, 0.625, 0.667 and 0.75), which are solid solutions found in the pseudo-binary phase diagram for Cu2Te and Ga2Te3. This system possesses tunable structural vacancy concentrations. The x= 0.5 phase, CuGaTe2, is nominally devoid of structural vacancies, while the rest of the compounds contain varying amounts of these features, and the volume density of vacancies increases with Ga2Te3 content. The sample with x = 0.5, 0.55, 0.571, 0.6, 0.625 crystallize in the chalcopyrite structure while the x = 0.667 and 0.75 adopt the Ga2Te3 defect zinc blende structure. Strong scattering of heat carrying phonons by structural defects, leads to the reduction of thermal conductivity, which is beneficial to the thermoelectric performance of materials. On the other hand, these defects also scatter charge carriers and reduce the electrical conductivity. All the samples investigated are p-type semiconductors as inferred by the signs of their respective Hall (RH) and Seebeck (S) coefficients. The structural vacancies were found to scatter phonons strongly, while a combination of increased carrier concentration, and vacancies decreases the Hall mobility ( H), degrading the overall thermoelectric performance. The room temperature H drops from 90 cm2/V s for CuGaTe2 to 13 cm2/V s in Cu9Ga11Te21 and 4.6 cm2/V s in CuGa3Te5. The low temperature thermal conductivity decreases significantly with higher Ga2Te3 concentrations (higher vacancy concentration) due to increased point defect scattering which dominate thermal resistance terms. At high temperatures, the dependence of thermal conductivity on the Ga2Te3 content is less significant. The presence of strong Umklapp scattering leads to low thermal conductivity at high temperatures for all samples investigated. The highest ZT among the samples in this study was found for the defect-free CuGaTe2 with ZT ~ 1.0 at 840K.
NSDL National Science Digital Library
Control the velocity of two sound sources in which the wave crests are visually represented. As the sound sources move, interference patterns and evidence of the Doppler effect can be observed and measured.
... chemotherapy and managing some of its side effects. Chemo Brain The mental cloudiness some people notice before, during, and after chemotherapy is commonly called chemo brain. Here you can find information on chemo brain ...
... Chapter . Additional information regarding the health effects of climate change and references to supporting literature can be found ... http://nca2014.globalchange.gov/report/sectors/human-health . Climate change, together with other natural and human-made health ...
Cross-plane Seebeck coefficient and Lorenz number in superlattices Z. Bian, M. Zebarjadi, R. Singh, Y. Ezzahri, and A. Shakouri
can be simply mea- sured by the dimensionless thermoelectric figure of merit ZT=S2 T/K, where higher thermo- electric figure of merits than their bulk counterparts. Here, we study the thermoelectric investigated. DOI: 10.1103/PhysRevB.76.205311 PACS number s : 73.50.Lw, 73.21.Cd I. INTRODUCTION Thermoelectric
Effect of NiSb on the thermoelectric properties of skutterudite CoSb3
NASA Astrophysics Data System (ADS)
Katsuyama, S.; Watanabe, M.; Kuroki, M.; Maehata, T.; Ito, M.
The phase equilibrium and thermoelectric properties of Co1-xNixSb3 ternary system were examined up to high nickel content x=0.40. NiSb compound with nickel arsenide structure was observed as the impurity phase in the samples with x>0.10 by x-ray diffraction. The sign of the Seebeck coefficient of Co1-xNixSb3 is negative, and the absolute value of the Seebeck coefficient and electrical resistivity generally decreases with increasing x. The thermal conductivity is reduced in the samples with x?0.06, but above x=0.06 it increases with increasing x. These behaviors of the thermoelectric properties in the samples with low nickel content are ascribed to the substituted Ni, while those in the samples with high nickel content are ascribed to the precipitated NiSb compound. In order to more reduce the thermal conductivity of the material, we have prepared a sintered CoSb3-NiSb composite where the NiSb particles are dispersed in the CoSb3 matrix by mechanical grinding and hot pressing. The thermal conductivity of the composite is lower than that of the Co1-xNixSb3 system especially at low temperature. The decrease of the thermal conductivity is ascribed to the enhancement of the phonon scattering caused by the dispersion of NiSb particles in the CoSb3 matrix.
The great improvement effect of pores on ZT in Co1-xNixSb3 system
Qinyu He; Shejun Hu; Xingui Tang; Yucheng Lan; Jian Yang; Xiaowei Wang; Zhifeng Ren; Qing Hao; Gang Chen
In this paper, the Co1-xNixSb3+y system (x=0.1,0.2; y=0, 0.05) has been prepared by direct current induced hot press and annealing. Pores were made by annealing pressed Co1-xNixSb3.05 pellets into Co1-xNixSb3 pellets during annealing. It was found that from room temperature to 500 ░C, the pores with diameter larger than 1 mum has significantly increased the Seebeck coefficient, considerably decreased the
NSDL National Science Digital Library
This animation provides a practical example of the impact of the Coriolis effect on daily life. After examining the animation, students can use a map or globe to locate where the pilots might have landed if they had followed their original flight path. They can then estimate how many miles the pilots have gone off their course. Students can also think about factors that navigators would consider when planning their flights and research the calculations used to account for the Coriolis effect. Although the resource was designed to accompany a specific Earth science textbook, it can be used without that text.
NSDL National Science Digital Library
This is a series of simulations of aspects of the photoelectric effect. There is an animation of the experiment with four choices of incident radiation - low and high intensity "red", to represent low energy light and low and high intensity "blue" to represent higher energy light. Electron production is animated and there is an ammeter to simulate current flow. Additional simulations show the effect of light frequency and intensity. There is a link to a spreadsheet that allows students to choose a sample from among five metals. The spreadsheet includes several questions to be answered after working through the materials.
Pearcy, R.W.; Bjoerkman, O.
This chapter examines the effects of CO/sub 2/ on plants at the physiological level. The authors examine the potential effects of elevated CO/sub 2/ in concert with water, temperature, light, and salinity. They also examine plant allometric growth as it is affected by CO/sub 2/. The relationships between CO/sub 2/ uptake and temperature are examined in some detail. Stomatal function as it is now known is discussed, along with changes in water use efficiency correlated with increased levels of CO/sub 2/. Future research needs are identified. 71 references, 8 figures.
Determination of ZT of PN thermoelectric couples by AC electrical measurement
Stefan Dilhaire; Luis-David Patino-Lopez; Stkphane Grauby; Jean-Michel Rampnoux; Stbastien Jorez; Wilfrid Claeys
In this work we use the thermoelectric coupling between Peltier and Seebeck effects to determine the ZT of a bismuth telluride thermoelectric couple. This coupling acts as thermal induction and produces a voltage drop induced by the Peltier thermal gradient in addition to the resistive voltage. In sine wave current excitation, the relative contribution of these two terms depends on
Generalized thermoelectric Thomson relations
L. I. Anatychuk; O. J. Luste
Thermoelectric Thomson relations interrelating the Seebeck, Peltier and Thomson coefficients were generalized for anisotropic thermoelectric media in magnetic field with regard for possible Umkehr effect. From the restrictions imposed by space and time symmetry on the properties of anisotropic media in magnetic field it was shown that the first Thomson relation relating the generalized Peltier coefficient ?* to the generalized
On the magnetotransport of 3D systems in quantizing magnetic field
NASA Astrophysics Data System (ADS)
Cheremisin, M. V.
The resistivity components of 3D electron gas placed in quantizing magnetic field are calculated taking into account the correction caused by combined action of the Peltier and Seebeck thermoelectric effects. The longitudinal, transverse and the Hall magnetoresistivities exhibit familiar 1/B-period oscillations being universal functions of magnetic field and temperature.
Thermoelectric properties of Mn-doped Ru2Si3
L. Ivanenko; A. Filonov; V. Shaposhnikov; A. Krivosheev; G. Behr; D. Souptel; J. Schumann; H. Vinzelberg; S. Paschen; A. Bentien; V. Borisenko
Pure and Mn-doped single crystals of ruthenium silicide (Ru2Si3) have been grown by floating zone technique with radiation heating in order to investigate the thermoelectric efficiency of this compound. Electrical resistivity, Hall effect, Seebeck coefficient and thermal conductivity of the crystals were measured at 100 - 900 K. Undoped crystals show in the thermoelectric power both types of conductivity. The
Waste-Heat thermoelectric power source for industrial wireless transmitters
Teerawat Thepmanee; Prasit Julsereewong; N. Taratanaphol
This paper presents Seebeck effect-based thermoelectric power source utilizing waste heat in manufacturing processes for industrial wireless transmitters. An industrial wireless transmitter can be supplied by its internal battery in combination with the proposed thermoelectric power source to conserve battery lifetime. Moreover, the proposed power source can operate as the backup power supply for new battery replacement without tuning the
Power and Efficiency Calculation in Commercial TEG and Application in Wasted Heat Recovery in Automobile
K. T. Zorbas; E. Hatzikraniotis; K. M. Paraskevopoulos
Thermoelectric generators (TEG) make use of the Seebeck effect in semiconductors for the direct conversion of heat into electrical energy, which is of particular interest for high reliability systems or for waste heat recovery. The generator efficiency, ?, is determined by comparing the amount of electricity produced (Pout) to the total amount of heat induced (Qin). A measuring system and
The Synthesis of CaZn2Sb2 and its Thermoelectric Properties Dan Stark, G. J. Snyder
extremely well by changing heat into electricity isentropically using the Seebeck and Peltier Cooling above 400║C. Introduction Device cooling and power generation have been areas of academic interest effects. Thermoelectrics can cool up to hundreds of degrees and handle large heat fluxes given
Appearance of thermochemical emf in some conducting materials
Y. S. Petrov; V. V. Maslikhov; V. D. Shcheglov
The appearance of an emf in conductors when they are heated is described by the Seebeck and Thompson effects. If some part of the surface of a conductor is covered by a pyrotechnical material and ignited, then while the pyrotechnical material is burning and after it has burned, an emf arises at the ends of the conductor. The direction of
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research
Pilon, Laurent
in power, refrigeration, and heat pump devices. In 2009, energy losses corresponded to more than 50, Stirling engines have been used in heat pump, cryogenic refrigeration, and air liquefaction applications [3]. Additionally, thermoelectric devices utilize the Seebeck effect to convert directly a steady-state temperature
Author's personal copy Pyroelectric waste heat energy harvesting using heat conduction
Pilon, Laurent
-product of power, refrigeration, or heat pump cycles according to the second law of thermodynamics [1]. In 2009 pump, cryogenic refrigeration, and air liquefaction applications [3]. Organic Rankine cycles use thermoelectric devices have been studied inten- sively. They make use of the Seebeck effect to convert a steady
Thermoelectric power generation for battery charging
Mahmudur Rahman; Roger Shuttleworth
Thermoelectric generators use the Seebeck effect to produce electrical power from a temperature difference caused by heat energy flow. In this paper the principle of using thermoelectrically converted heat energy for powering portable electronic equipment or charging its battery has been investigated for a lap-top computer. The thermoelectric battery charger developed, consists of a thermoelectric converter system, powered from butane
Optimization of Dimensionless Figure of Merit in Oxide Thin Film Thermoelectrics
Daniel Osborne; Scott Huxtable; Ashutosh Tiwari; Jeremiah Abiade
The ability of uniquely functional thermoelectric materials to convert waste heat directly into electricity is critical considering the global energy economy. Profitable, energy-efficient thermoelectrics possess thermoelectric figures of merit ZT >= 1. We examined the effect of metal nanoparticle -- oxide film interfaces on the thermal conductivity kappa and Seebeck coefficient S in bilayer and multilayer thin film oxide thermoelectrics
Soret motion in non-ionic binary molecular mixtures Yves Leroyer and Alois Wrger
Boyer, Edmond
. For charged colloids in an electrolyte solution, several mechanisms have been singled out: The temperature gra the particle to the cold [9]. On the other hand, the Seebeck effect of the electrolyte solution induces vari- ation with the salinity and the pH value [11, 12]. Surprisingly, the situation is less clear
NSDL National Science Digital Library
This set of four animated slides illustrates the Coriolis effect, a manifestation of one of Newton's laws which says that objects move in a straight line, in an "inertial" frame of reference, unless acted upon by a force. The slides use the analogy of a ball thrown on a rotating carousel.
NASA Technical Reports Server (NTRS)
Teays, Terry
The cause of the Blazhko effect, the long-term modulation of the light and radial velocity curves of some RR Lyr stars, is still not understood. The observational characteristics of the Blazhko effect are discussed. Some preliminary results are presented from two recent campaigns to observe RR Lyr, using the International Ultraviolet Explorer along with ground-based spectroscopy and photometry, throughout a pulsation cycle, at a variety of Blazhko phases. A set of ultraviolet light curves have been generated from low dispersion IUE spectra. In addition, the (visual) light curves from IUE's Fine Error Sensor are analyzed using the Fourier decomposition technique. The values of the parameters Psi(sub 21) and R(sub 21) at different Blazhko phases of RR Lyr span the range of values found for non-Blazhko variables of similar period.
Bruce R. Wheaton
When electromagnetic radiation strikes a metal, ? electrons are released. This simple statement hides a considerable history\\u000a stretching back to Galvani and not plumbed entirely to this day.\\u000a \\u000a In its initial form, the effect was discovered by Heinrich Hertz (1857¢94) during his path-breaking corroboration of Maxwell's\\u000a laws in 1887. He was using spark-discharges in one part of his laboratory in
The effects of metabolic inhibitors and ouabain on alanine trans- port across rabbit ileum, in vitro, have been investigated. Net transport of alanine and Na across short-circuited segments of ileum is virtually abolished by cyanide, 2,4-dinitrophenol, iodoacetate, and ouabain. However, these inhibitors do not markedly depress alanine influx from the mucosal solution, across the brush border, into the intestinal epithelium,
NSDL National Science Digital Library
In this activity, by the Concord Consortium's Molecular Literacy project, students explore the piezoelectric effect, which is the conversion between electricity and mechanical motion. The model used in this activity shows this conversion and users can manipulate the model to change the voltage and observe changes to a crystal. The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In these activities, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity and central and key concepts.
NASA Technical Reports Server (NTRS)
2003-01-01[figure removed for brevity, see original site] The impact crater in this THEMIS image is a model illustration to the effects of erosion on Mars. The degraded crater rim and several landslides observed in crater walls is evidence to the mass wasting of materials. Layering in crater walls also suggests the presence of materials that erode at varying rates.Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.Image information: VIS instrument. Latitude 31.6, Longitude 44.3 East (315.7 West). 19 meter/pixel resolution.
Effects of Bi on the thermoelectric properties of Mg2Si-Mg2Ge solid solutions
NASA Astrophysics Data System (ADS)
You, Sin-Wook; Shin, Dong-Kil; Kim, Il-Ho
Mg2Si1- x Ge x :Bi m (0.3 ? x ? 0.7, m = 0 or 0.02) solid solutions were synthesized by using a solid-state reaction (SSR) and were consolidated by hot pressing (HP). In the case of the undoped Mg2Si1- x Ge x specimens, the electrical conduction changed from n-type to p-type at room temperature for x ? 0.7 due to the intrinsic properties of Mg2Ge. The electrical conductivity rapidly increased with increasing temperature, indicating a non-degenerate semiconducting behavior, and decreased with increasing Ge content. However, all Bi-doped Mg2Si1- x Ge x solutions showed n-type conduction. The carrier concentration was increased from 4.0 ū 1017 to 1.9 ū 1020 cm-3 by Bi doping, and the electrical conductivity was increased from 7.3 ū 10 to 4.3 ū 104 Sm-1. The absolute value of the Seebeck coefficient increased with increasing temperature, and the Seebeck coefficient ranged from -91 to -224 ?VK-1 for the Bi-doped specimens. Bi doping reduced the thermal conductivities of the Mg2Si1- x Ge x solid solutions at temperatures above 723 K. Mg2Si0.7Ge0.3:Bi0.02 exhibited a maximum dimensionless figure-of-merit of 0.79 at 823 K.
Not Available
Concerns about global warming stem from mounting scientific evidence that increasing concentrations of carbon dioxide and other trace gases produce by man are starting to alter the earth's temperature. This report provides information on the scientific understanding of the global warming phenomenon and DOE's research efforts to fill information gaps on the issue, the nature of program planning and criteria used by DOE for evaluating global warming research and development, DOE leadership on the global warming issue and efforts to integrate its various activities into energy policy and planning considerations, and proposed policy and/or program changes made by responsible agencies or groups for improving energy efficiency and/or reducing energy-related emission with potential climate change effects.
Effect of Y doping on magnetic and transport properties of La0.7Sr0.3CoO3
NASA Astrophysics Data System (ADS)
Dwivedi, G. D.; Shukla, K. K.; Shahi, P.; Jha, O. K.; Ghosh, A. K.; Nigam, A. K.; Chatterjee, Sandip
The temperature variation of magnetization, resistivity and thermo electric power of undoped and Y-doped La0.7Sr0.3CoO3 samples have been investigated. Y-doping decreases the magnetization possibly due to the spin state transition of Co-ions. The low temperature conduction in (La1-yYy)0.7Sr0.3CoO3 is consistent with the variable range hopping. With Y doping, value of the Seebeck coefficient increases, as Y doping decreases bandwidth and increases distortion.
Effect of C-face 4H-SiC(0001) deposition on thermopower of single and multilayer graphene in AA, AB and ABC stacking
NASA Astrophysics Data System (ADS)
Wierzbowska, Ma?gorzata; Dominiak, Adam; Pizzi, Giovanni
The Seebeck coefficient in multilayer graphene is investigated within the density-functional theory, using the semiclassical Boltzmann equations and interpolating the bands in a maximally-localized Wannier functions basis set. We compare various graphene stackings (AA, AB and ABC) both free-standing and deposited on the 4H-SiC(0001) C-terminated substrate. We find that the presence of the SiC substrate can significantly affect the thermopower properties of graphene layers, depending on the stacking, providing a promising way to tailor efficient graphene-based devices.
Development of Flexible Micro-Thermo-electrochemical Generators Based on Ionic Liquids
NASA Astrophysics Data System (ADS)
Uhl, Stefanie; Laux, Edith; Journot, Tony; Jeandupeux, Laure; Charmet, Jķr¶me; Keppner, Herbert
The unfavourable relationship between electrical and thermal conductivity limits the choice of solid-state materials for thermoelectric generators (TEG). Among ionic liquids (IOL), it appears that a large variety of thermoelectric (TE) materials with promising high Seebeck coefficients have potential for development. Furthermore, the novel solid-on-liquid deposition technology (SOLID) allows the encapsulation of liquid TE materials to create new, highly integrated TEG devices. Following this vision, this paper studies a large number of IOLs looking at TE-relevant parameters such as thermal and electrical conductivity, Seebeck coefficient and temperature-dependent viscosity. We show that positive and negative Seebeck coefficients can be obtained, depending on the molecular structure and the viscosity of the IOL. The properties of single-junction TEGs are presented in terms of I- V characteristics correlated with the IOL properties. We prove that the limiting effect of conversion efficiency is the current density that can be extracted from a device rather than the Seebeck coefficient.
Lamborg, M.R.; Hardy, R.W.F.; Paul, E.A.
The postulated doubling of atmospheric CO/sub 2/ is not likely to have direct effect on soil microbial activity because during the growing season, the concentration of CO/sub 2/ in the soil atmosphere is already ten to fifty times higher than existing atmospheric CO/sub 2/. Based on all available experimental information, it is estimated that a doubling of atmospheric CO/sub 2/ will cause an increase in primary productivity of 10 to 40% depending on locale. The increase in biomass will, in turn, produce a limitation of available soil nutrients, especially nitrogen and phosphorus. Increased organic carbon together with nitrogen and/or phosphorus limitation will result in a preferential increase in nitrogen fixation and mycorrhizal activities as the expedient means for supplying required nutrients to sustain the predicted increase in primary productivity. Therefore, increased emphasis should be placed on fundamental research related to soil microbiology with special reference to nitrogen-fixing, nitrifying and denitrifying bacteria, and to the mycorrhizal fungi. 111 references, 2 figures.
Thermoelectric power of small polarons in magnetic semiconductors
Liu, N.H.; Emin, D.
The thermoelectric power (Seebeck coefficient) ..cap alpha.. of a small polaron in both ferromagnetic and antiferromagnetic semiconductors and insulators is calculated for the first time. In particular, we obtain the contribution to the Seebeck coefficient arising from exchange interactions between the severely localized carrier (i.e., small polaron) of charge q and the spins of the host lattice. In essence, we study the heat transported along with a carrier. This heat, the Peltier heat, Pi, is related to the Seebeck coefficient by the Kelvin relation: Pi = qT..cap alpha.., where T is the temperature. The heat per carrier is simply the product of the temperature and the change of the entropy of the system when a small polaron is added to it. The magnetic contribution to the Seebeck coefficient is therefore directly related to the change of the magnetic entropy of the system upon introduction of a charge carrier. We explicitly treat the intrasite and intersite exchange interactions between a small polaron and the spins of a spin-1/2 system. These magnetic interactions produce two competing contributions to the Seebeck coefficient. First, adding the carrier tends to provide extra spin freedom (e.g., spin up or spin down of the carrier). This effect augments the entropy of the system, thereby producing a positive contribution to the Peltier heat. Second, however, the additional exchange between the carrier and the sites about it enhances the exchange binding among these sites. This generally reduces the energetically allowable spin configurations. The concomitant reduction of the system's entropy provides a negative contribution to the Peltier heat. At the highest of temperatures, when kT exceeds the intrasite exchange energy, the first effect dominates. Then, the Peltier heat is simply augmented by kT ln2.
Effects of High Magnetic Fields on Microstructures and Thermoelectric Properties of Zn-Sb Alloy
NASA Astrophysics Data System (ADS)
Yuan, Yi; Mao, Jun; Liu, Tie; Tahashi, Masahiro; Wang, Qiang; He, Jicheng
Several samples of Zn-Sb alloys, composed with ?-Zn4Sb3 and Zn phases, were prepared by solidification under high magnetic fields (HMFs). The microstructure evolution and thermoelectric (TE) properties of the alloys were then investigated. Zn phase precipitated as strip and presented reticulation structure in the samples without HMFs. When the HMFs were imposed, Zn became disperse and the strip of Zn became thinner and shorter. In addition, the c-axis of Zn crystals showed a tendency to orientate toward the direction perpendicular to the magnetic field direction. The samples prepared under HMFs had higher resistivity and Seebeck coefficient and lower thermal conductivity. When compared to the solidified samples without HMFs, the application of 8.8 T of HMF increased the maximum figure of merit 3.7 times. In addition, the relationship between microstructure and TE properties was also analyzed.
Effect of Biaxial Strain on Electronic and Thermoelectric Properties of Mg2Si
NASA Astrophysics Data System (ADS)
Balout, Hilal; Boulet, Pascal; Record, Marie-Christine
The electronic and thermoelectric properties of biaxially strained magnesium silicide Mg2Si are analyzed by means of first-principle calculations and semiclassical Boltzmann theory. Electron and hole doping are examined for different doping concentrations and temperatures. Under strain the degeneracy of the electronic orbitals near the band edges is removed, the orbital bands are warped, and the energy gap closes up. These characteristics are rationalized in the light of the electron density transfers upon strain. The electrical conductivity increases with the biaxial strain, whereas neither the Seebeck coefficient nor the power factor (PF) follow this trend. Detailed analysis of the evolution of these thermoelectric properties is given in terms of the in-plane and cross-plane components. Interestingly, the maximum value of the PF is shifted towards lower temperatures when increasingly intensive strain is applied.
Quenched phonon drag in silicon nanowires reveals significant effect in the bulk at room temperature.
Sadhu, Jyothi; Tian, Hongxiang; Ma, Jun; Azeredo, Bruno; Kim, Junhwan; Balasundaram, Karthik; Zhang, Chen; Li, Xiuling; Ferreira, P M; Sinha, S
Existing theory and data cannot quantify the contribution of phonon drag to the Seebeck coefficient (S) in semiconductors at room temperature. We show that this is possible through comparative measurements between nanowires and the bulk. Phonon boundary scattering completely quenches phonon drag in silicon nanowires enabling quantification of its contribution to S in bulk silicon in the range 25-500 K. The contribution is surprisingly large (?34%) at 300 K even at doping of ?3 ū 10(19) cm(-3). Our results contradict the notion that phonon drag is negligible in degenerate semiconductors at temperatures relevant for thermoelectric energy conversion. A revised theory of electron-phonon momentum exchange that accounts for a phonon mean free path spectrum agrees well with the data. PMID:25831487
Feedback Effects 1 Running Head: FEEDBACK EFFECTS
Maddox, W. Todd
Feedback Effects 1 Running Head: FEEDBACK EFFECTS Feedback and Stimulus-Offset Timing Effects We examined how feedback delay and stimulus offset timing affected declarative, rule-based and procedural, information-integration category-learning. We predicted that small feedback delays of several
Ecological Effects in Malaria Vaccine Effectiveness in
Doyle, Martin
Ecological Effects in Malaria Vaccine Effectiveness in Lilongwe, Malawi Cameron Taylor B component to a GlaxoSmithKline phase III trial vaccine trial so that researchers can better understand distribution and the ecological effects of both malaria transmission intensity and vaccine efficacy
Effects of Thermal Annealing on the Thermoelectric and Optical Properties of SiO2/SiO2+Cu Nanolayer Thin Films
NASA Astrophysics Data System (ADS)
Budak, S.; Baker, M.; Lassiter, J.; Smith, C.; Muntele, C.; Johnson, R. B.
We have prepared multi-nanolayer superlattice thin-film systems comprising 36 alternating layers of SiO2 and SiO2+Cu nanolayers, of total thickness approximately 300 nm, by magnetron direct current-radio frequency sputtering. To modify their thermoelectric and optical properties, the films were placed in a furnace for annealing at temperatures between 500░C and 700░C, in air, for 1 h, to form quantum nano-dots and/or quantum clusters. Atomic force microscopy was used to analyze the surface of the thin-film systems. The thermoelectric and optical properties of the systems were characterized by study of ultraviolet-visible-near infrared absorption, fluorescence, and Raman spectroscopy, and by measurement of Seebeck coefficients. Seebeck coefficients increased from -70 ?V/K to -100 ?V/K when the temperature was increased from 0░C to 700░C. Optical absorption spectra showed that formation of nano-dots and/or nano-clustering also occurred as the temperature was increased. Thermal annealing affected the optical and thermal properties of the multi-nanolayer thermoelectric thin-film systems in the positive direction.
Effects of Thermal Annealing on the Thermoelectric and Optical Properties of SiO2/SiO2+Cu Nanolayer Thin Films
NASA Astrophysics Data System (ADS)
Budak, S.; Baker, M.; Lassiter, J.; Smith, C.; Muntele, C.; Johnson, R. B.
We have prepared multi-nanolayer superlattice thin-film systems comprising 36 alternating layers of SiO2 and SiO2+Cu nanolayers, of total thickness approximately 300 nm, by magnetron direct current-radio frequency sputtering. To modify their thermoelectric and optical properties, the films were placed in a furnace for annealing at temperatures between 500░C and 700░C, in air, for 1 h, to form quantum nano-dots and/or quantum clusters. Atomic force microscopy was used to analyze the surface of the thin-film systems. The thermoelectric and optical properties of the systems were characterized by study of ultraviolet-visible-near infrared absorption, fluorescence, and Raman spectroscopy, and by measurement of Seebeck coefficients. Seebeck coefficients increased from -70 ?V/K to -100 ?V/K when the temperature was increased from 0░C to 700░C. Optical absorption spectra showed that formation of nano-dots and/or nano-clustering also occurred as the temperature was increased. Thermal annealing affected the optical and thermal properties of the multi-nanolayer thermoelectric thin-film systems in the positive direction.
Onsager relations in coupled electric, thermoelectric, and spin transport: The tenfold way
NASA Astrophysics Data System (ADS)
Jacquod, Philippe; Whitney, Robert S.; Meair, Jonathan; B³ttiker, Markus
Hamiltonian systems can be classified into ten classes, in terms of the presence or absence of time-reversal, particle-hole, and sublattice/chiral symmetries. We construct a quantum coherent scattering theory of linear transport for coupled electric, heat, and spin transport; including the effect of Andreev reflection from superconductors. We derive a complete list of the Onsager reciprocity relations between transport coefficients for coupled electric, spin, thermoelectric and spin caloritronic effects. We apply these to all ten symmetry classes, paying special attention to specific additional relations that follow from the combination of symmetries, beyond microreversibility. We discuss these relations in several illustrative situations. We show the reciprocity between spin-Hall and inverse spin-Hall effects, and the reciprocity between spin-injection and magnetoelectric spin currents. We discuss the symmetry and reciprocity relations of Seebeck, Peltier, spin Seebeck, and spin Peltier effects in systems with and without coupling to superconductors.
Adequacy for Algebraic EffectsĀ
Plotkin, Gordon; Power, John
Moggi proposed a monadic account of computational effects. He also presented the computational lamda-calculus, c, a core call-by-value functional programming language for effects; the effects are obtained by adding ...
... My Bridge 4 Life Clinical Trials Guides Newsletters Nutrition & Wellness PCF Spotlight Glossary African American Men Living with Prostate Cancer Side Effects of Chemotherapy Side Effects Urinary Dysfunction ...
Small-polaron versus band conduction in some transition-metal oxides
A. J. Bosman; H. J. van Daal
In this paper an attempt is made to establish the nature of free charge carriers and of charge carriers bound to centres in p-type NiO, CoO and MnO and in n-type MnO and ?-Fe2O3.For free charge carriers, d.c. conductivity, Seebeck coefficient and Hall effect are considered. Effects arising from inhomogeneous conduction and impurity conduction are discussed. Impurity conduction appears to
Dimensional Analysis of Thermoelectric Modules Under Constant Heat Flux
NASA Astrophysics Data System (ADS)
Suzuki, Ryosuke O.; Fujisaka, Takeyuki; Ito, Keita O.; Meng, Xiangning; Sui, Hong-Tao
Thermoelectric power generation is examined in the case of radiative heating. A constant heat flux is assumed in addition to consideration of the Seebeck effect, Peltier effect, and Joule heating with temperature-dependent material properties. Numerical evaluations are conducted using a combination of the finite-volume method and an original simultaneous solver for the heat transfer, thermoelectric, and electric transportation phenomena. Comparison with experimental results shows that the new solver could work well in the numerical calculations. The calculations predict that the Seebeck effect becomes larger for longer thermoelectric elements because of the larger temperature difference. The heat transfer to the cold surface is critical to determine the junction temperatures under a constant heat flux from the hot surface. The negative contribution from Peltier cooling and heating can be minimized when the current is smaller for longer elements. Therefore, a thicker TE module can generate more electric power even under a constant heat flux.
Thermoelectric transport of mesoscopic conductors coupled to voltage and thermal probes
NASA Astrophysics Data System (ADS)
Sßnchez, David; Serra, Llorenń
We investigate the basic properties of the thermopower (Seebeck coefficient) of phase-coherent conductors under the influence of dephasing and inelastic processes. Transport across the system is caused by a voltage bias or a thermal gradient applied between two terminals. Inelastic scattering is modeled with the aid of an additional probe acting as an ideal potentiometer and thermometer. We find that inelastic scattering reduces the conductor's thermopower and, more unexpectedly, generates a magnetic field asymmetry in the Seebeck coefficient. The latter effect is shown to be a higher-order effect in the Sommerfeld expansion. We discuss our result by using two illustrative examples. First, we consider a generic mesoscopic system described within random matrix theory and demonstrate that thermopower fluctuations disappear quickly as the number of probe modes increases. Second, the asymmetry is explicitly calculated in the quantum limit of a ballistic microjunction. We find that asymmetric scattering strongly enhances the effect and discuss its dependence on temperature and Fermi energy.
Budker, Dmitry
Dysprosium Nathan Leefer #12;Background Sokolov Effect Conclusions Outline 1 Background Neutral Hydrogen Stark Effect Hydrogen Atom Interferometer 2 Sokolov Effect Pamir Broken Theories Summary Dysprosium 3 Sokolov Effect Conclusions Pamir Broken Theories Summary Dysprosium Measurement of Lamb Shift Pamir Nathan
ERIC Educational Resources Information Center
Kelley, Ken; Preacher, Kristopher J.
The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension,ģ
Improving School Effectiveness.
ERIC Educational Resources Information Center
MacBeath, John, Ed.; Mortimore, Peter, Ed.
School effectiveness is an issue that has preoccupied researchers and policymakers for 3 decades. To study how ineffective schools become effective and what constitutes an effective school, the Improving School Effectiveness Project was carried out in Scotland from 1995 to 1997. This project forms the basis of discussion in this book, which has 11ģ
NSDL National Science Digital Library
Ms. Ufomadu
Cause and Effect practice to build skill knowledge for the reading portion of the graduation exam. Complete the Cause and Effect activities at your pace . Cause and Effect Match , Cause and Effect Mini Lesson and Game , What s the Cause?? Quiz . ...
James Q. Quach
We derive the gravitonic Casimir effect with non-idealised boundary conditions. This allows the quantification of the gravitonic contribution to the Casimir effect from real bodies. We quantify the meagreness of the gravitonic Casimir effect in ordinary matter. We also quantify the enhanced effect produced by the speculated Heisenberg-Couloumb (H-C) effect in superconductors, thereby providing a test for the validity of the H-C theory, and consequently the existence of gravitons.
Kelley, Ken; Preacher, Kristopher J
The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension, measure/index, and value), outline 10 corollaries that follow from our definition, and review ideal qualities of effect sizes. Our definition of effect size is general and subsumes many existing definitions of effect size. We define effect size as a quantitative reflection of the magnitude of some phenomenon that is used for the purpose of addressing a question of interest. Our definition of effect size is purposely more inclusive than the way many have defined and conceptualized effect size, and it is unique with regard to linking effect size to a question of interest. Additionally, we review some important developments in the effect size literature and discuss the importance of accompanying an effect size with an interval estimate that acknowledges the uncertainty with which the population value of the effect size has been estimated. We hope that this article will facilitate discussion and improve the practice of reporting and interpreting effect sizes. PMID:22545595
Peltier Cooling and Onsager Reciprocity in Ferromagnetic Thin Films
NASA Astrophysics Data System (ADS)
Avery, A. D.; Zink, B. L.
We present direct measurements of the Peltier effect as a function of temperature from 77 to 325 K in Ni, Ni80Fe20, and Fe thin films made using a suspended Si-N membrane structure. Measurement of the Seebeck effect in the same films allows us to directly test predictions of Onsager reciprocity between the Peltier and Seebeck effects. The Peltier coefficient ? is negative for both Ni and Ni80Fe20 films and positive for the Fe film. The Fe film also exhibits a peak associated with the magnon drag Peltier effect. The observation of magnon drag in the Fe film verifies that the coupling between the phonon, magnon, and electron systems in the film is the same whether driven by heat current or charge current. The excellent agreement between ? values predicted using the experimentally determined Seebeck coefficient for these films and measured values offers direct experimental confirmation of the Onsager reciprocity between these thermoelectric effects in ferromagnetic thin films near room temperature.
Peltier cooling and onsager reciprocity in ferromagnetic thin films.
Avery, A D; Zink, B L
We present direct measurements of the Peltier effect as a function of temperature from 77 to 325 K in Ni, Ni(80)Fe(20), and Fe thin films made using a suspended Si-N membrane structure. Measurement of the Seebeck effect in the same films allows us to directly test predictions of Onsager reciprocity between the Peltier and Seebeck effects. The Peltier coefficient ? is negative for both Ni and Ni(80)Fe(20) films and positive for the Fe film. The Fe film also exhibits a peak associated with the magnon drag Peltier effect. The observation of magnon drag in the Fe film verifies that the coupling between the phonon, magnon, and electron systems in the film is the same whether driven by heat current or charge current. The excellent agreement between ? values predicted using the experimentally determined Seebeck coefficient for these films and measured values offers direct experimental confirmation of the Onsager reciprocity between these thermoelectric effects in ferromagnetic thin films near room temperature. PMID:24093285
Aulas, J-J
The word placebo appeared for the first time in an English medical dictionary in 1785. In French, it appeared much latter in 1958. This word defines an experimental tool used for rigourous evaluation of a specific effect of pharmacological treatment and the non specific effect of any therapy. The placebo effect is the strictly psychological or psychophysiological effect of a placebo. The two principal components of placebo effect as a pain killer, which has been extensively studied in this field, are positive expectancies of both the patient and the physician. Although the mechanisms of action of placebo effect are not well understood, results of several recent works are particularly interesting. PMID:16292233
Anatolij Dvure?enskij
We define a new class of pseudo effect algebras, called kite pseudo effect algebras, which is connected with partially ordered groups not necessarily with strong unit. In such a case, starting even with an Abelian po-group, we can obtain a noncommutative pseudo effect algebra. We show how such kite pseudo effect algebras are tied with different types of the Riesz Decomposition Properties. Kites are so-called perfect pseudo effect algebras, and we define conditions when kite pseudo effect algebras have the least non-trivial normal ideal.
Molecular Dynamics Simulation of the Phonon Conductivity in Cu-Ni Binary Alloy
NASA Astrophysics Data System (ADS)
Konishi, Yusuke; Fukushima, Tetsuya; Sato, Kazunori; Asai, Yoshihiro; Katayama-Yoshida, Hiroshi
In 2010, a giant Peltier effect was observed in a Cu-Ni/Au junction. It is considered that this giant Peltier effect is caused by nano-scale phase separation formed in the sputtering process. The giant Peltier coefficient in the Cu-Ni/Au junction indicates the great Seebeck coefficient in Cu-Ni alloy. Although this alloy is a prospective thermoelectric material because of its great Seebeck coefficient, the low phonon thermal conductivity is also necessary for a large thermoelectric coefficient ZT. In order to find conditions for the low phonon conductivity, we calculate the thermal conductivity in Cu-Ni Alloy in various shapes with or without nanostructures by using nonequilibrium molecular dynamics simulation. In this simulation, we use a semi-empirical potential and the reverse nonequilibrium molecular dynamics method.
Modeling thermoelectric transport in organic materials.
Wang, Dong; Shi, Wen; Chen, Jianming; Xi, Jinyang; Shuai, Zhigang
Thermoelectric energy converters can directly convert heat to electricity using semiconducting materials via the Seebeck effect and electricity to heat via the Peltier effect. Their efficiency depends on the dimensionless thermoelectric figure of merit of the material, which is defined as zT = S(2)?T/? with S, ?, ?, and T being the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature respectively. Organic materials for thermoelectric applications have attracted great attention. In this review, we present our recent progress made in developing theories and computational schemes to predict the thermoelectric figure of merit at the first-principles level. The methods have been applied to model thermoelectric transport in closely-packed molecular crystals and one-dimensional conducting polymer chains. The physical insight gained in these studies will help in the design of efficient organic thermoelectric materials. PMID:23086525
Thermoelectric properties of tungsten-substituted Heusler Fe2VAl alloy
NASA Astrophysics Data System (ADS)
Mikami, M.; Kinemuchi, Y.; Ozaki, K.; Terazawa, Y.; Takeuchi, T.
A Heusler Fe2V1-xWxAl sintered alloy was synthesized to evaluate the effect of W substitution on thermoelectric properties of the Heusler alloy. The Seebeck coefficient and the electrical conductivity are simultaneously enhanced through electron injection resulting from the W substitution. Comparison with the Si-substituted Fe2VAl alloy reveals that the additional electronic states derived from W 5d orbital in the vicinity of pseudogap are likely to degrade the Seebeck coefficient. Thermal conductivity is effectively reduced by the W substitution because of the large atomic mass and volume of W compared to the constituent elements of Fe2VAl alloy. The appreciable reduction of thermal conductivity, without a serious deterioration in electrical conduction, enhances the thermoelectric figure of merit in the Heusler alloy.
Howard, Jeff W.
As a 4-H volunteer, you will have different functions. An especially important task is to prepare interesting and effective meetings where youth can obtain the greatest educational benefit while having fun. This publication outlines effective...
Howard, Jeff W.
As a 4-H volunteer, you will have different functions. An especially important task is to prepare interesting and effective meetings where youth can obtain the greatest educational benefit while having fun. This publication outlines effective...
ERIC Educational Resources Information Center
Caraway, James E.
The author discusses other writings on effective college teaching and then presents his list of necessary characteristics for the effective teacher, stressing the interpersonal dimension of the teaching-learning situation. (MF)
Stormwater BMP Effectiveness Toolkit
US EPA has identified the effectiveness of Stormwater Best Management Practices (BMPs) as a priority research need. Effective protection of biotic integrity requires that processes maintaining the diversity of physical habitats be protected. Methods are needed to evaluate the e...
... cancer care is relieving side effects, called symptom management, palliative care, or supportive care. It is important ... treat them. To learn about the symptoms and management of the long-term side effects of cancer ...
December 2006 MAINTAINING EFFECTIVE
December 2006 MAINTAINING EFFECTIVE INFORMATION TECHNOLOGY (IT) SECURITY THROUGH TEST, TRAINING, AND EXERCISE PROGRAMS MAINTAINING EFFECTIVE INFORMATION TECHNOLOGY (IT) SECURITY THROUGH TEST, TRAINING, AND EXERCISE PROGRAMS Shirley Radack, EditorShirley Radack, Editor Computer Security DivisionComputer Security
P Gregory
SummariesĀĀAn unusual effect colourant is one that exhibits a colour change or some other unusual effect outside the traditional colour-imparting\\u000a properties of a colourant. Il also includes novel ways of producing colour.\\u000a \\u000a Many such effects are known and commercialised. For example, holograms and optically-variable pigments, which utilise the\\u000a interference of visible light, and the electrostatic and photoconductive effects used in
Hamiltonians of strain effects
NASA Astrophysics Data System (ADS)
Suzuki, Tatsuo
Hamiltonians that generally describe the effects of strain are proposed. The strain effects can be calculated easily from the unstrained potential using these Hamiltonians. These Hamiltonians are valid when the strain is spatially modulated, and are also valid when the strain exists in a magnetic field. These Hamiltonians can also be used in the improved effective mass approximation.
ERIC Educational Resources Information Center
Sartori, Leo
Fundamental principles governing nuclear explosions and their effects are discussed, including three components of a nuclear explosion (thermal radiation, shock wave, nuclear radiation). Describes how effects of these components depend on the weapon's yield, its height of burst, and distance of detonation point. Includes effects of threeģ
Finite elements for thermoelectric device analysis in ANSYS
Elena E. Antonova; David C. Looman
A new set of ANSYS coupled-field elements enables users to accurately and efficiently analyze thermoelectric devices. This paper reviews the finite element formulation, which, in addition to Joule heating, includes Seebeck, Peltier, and Thomson effects. Examples of steady-state and transient simulations of a thermoelectric generator and a single-stage Peltier cooler are presented for thermoelectric analysis verification. An analysis of a
New Concept of Laboratory Exercise on Temperature Measurements Using Thermocouple
NASA Astrophysics Data System (ADS)
Slavata, Old?ich; Sou?ek, Pavel; Holub, Jan
The proposed exercise is focused on the measurement of temperature using thermocouple, students acquire theoretical knowledge of the Seebeck effect, the design and application of thermocouples including the differences between their various types. The students measure the voltage at the thermocouple by various methods: directly with a compensation box, using operational amplifiers and USB module. The exercise explains also general principles of low voltage measurements, error compensation and uncertainty evaluation.
Thermoelectric Properties of Lanthanum Sulfide
NASA Technical Reports Server (NTRS)
Wood, C.; Lockwood, R.; Parker, J. B.; Zoltan, A.; Zoltan, L. D.; Danielson, L.; Raag, V.
Report describes measurement of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect in gamma-phase lanthanum sulfide with composition of La3-x S4. Results of study, part of search for high-temperature thermoelectric energy-conversion materials, indicate this sulfide behaves like extrinsic semiconductor over temperature range of 300 to 1,400 K, with degenerate carrier concentration controlled by stoichiometric ratio of La to S.
Transverse thermoelectric devices
C. Reitmaier; F. Walther; H. Lengfellner
Multilayer structures A¢B¢A??? consisting of alternating layers of a metal A and a semiconductor B can show large anisotropy\\u000a in their transport properties. In tilted multilayer structures, where layer planes and sample surface include a nonzero tilt\\u000a angle, nonvanishing off-diagonal elements in the sampleÆs transport tensors lead to transverse Seebeck and Peltier effects.\\u000a Achievable temperature differences and figures of merit
Absolute self-calibrated room-temperature terahertz powermeter.
Pradere, Christophe; Caumes, Jean-Pascal; Toutain, Jean; Abraham, Emmanuel; Chassagne, Bruno; Batsale, Jean-Christophe
Coupling optical and thermal properties of a terahertz (THz) thermal converter based on the Seebeck effect provides an unsupplied room-temperature measuring device dedicated to THz power metrology. Performance characteristics such as broadband response (0-30 THz), high sensitivity (<25 ?WĘHz(-0.5)), and the possibility to develop an internal absolute self-calibration estimated at 9.93 WĘV(-1) are reported. Advantages and drawbacks of this THz powermeter are discussed. PMID:23670761
Luque, Gloria M; Giraud, Tatiana; Courchamp, Franck
1. Allee effects occur when the aggregation of individuals result in mutually beneficial intraspecific interactions whereby individual fitness, or per capita growth rate, increases with the number of individuals. Allee effects are common in social species due to their cooperative behaviours, such as breeding, feeding or defence. Allee effects have important implications for many aspects of basic and applied ecology. Over the past decades, the study of Allee effects has influenced population dynamics, community ecology, endangered species management and invasion biology. 2. Despite the fact that cooperation is the basis of their social structure, Allee effects have received little attention among eusocial insects. Extreme cooperation is common, and reproductive specialization of individuals occurs due to division of labour. These life-history traits suggest that the potential contribution of each caste to reproduction and survival may be differential and nonadditive. 3. We studied Allee effects in the invasive Argentine ant (Linepithema humile). In this species, many queens and workers are present in colonies, which allowed us to explore the differential effects of castes on the presence of Allee effects. In the laboratory, we measured brood production and individual survival in experimental colonies that differed in the initial numbers of queens and workers.4. Our results highlight the differential effect of queens and workers on survival and productivity. We found three positive density-dependent relationships indicative of component Allee effects at the colony level: both workers and queens had a positive effect on the productivity of the other caste, and queens had a positive effect on worker survivorship. 5. Our experimental results suggest a potential positive feedback between worker and queen abundance, which may have contributed to the evolution of large colony sizes. Our study provides the first evidence of Allee effects in eusocial insects and highlights the need to consider castes separately in population dynamics. Division of labour and differential reproductive rates are factors that should be integrated into the study of Allee effects. PMID:23672650
The butterfly effect of the "butterfly effect".
Dooley, Kevin J
The "Butterfly Effect" metaphor states with variance that the flap of a butterfly's wings in Brazil can cause a tornado in Texas. This metaphor has become part of the common vernacular of Western culture. In this paper I discuss the origins of the metaphor, examine its current usage within popular culture, and present an argument as to why it is popular. I propose that the metaphor is a type of semantic attractor, a narrative device with invariant meaning but audience-specific contextualization. Finally I address whether the Butterfly Effect metaphor is a good example of itself. PMID:19527619
The central role of the Peltier coefficient in thermoelectric cooling
NASA Astrophysics Data System (ADS)
Garrido, J.; Casanovas, A.
This paper discusses the special role that the Peltier effect plays in thermoelectric cooling. From a particular energy balance for a thermocouple, we can conclude that the Peltier component pumps out the energy of all other terms: Joule, Fourier, Seebeck, and thermoelectric cooling. We emphasize also that in this energy balance, there is a need to include a new contribution, named after Seebeck that usually is not considered in the literature. We discuss a new method to evaluate the Peltier coefficient using measurements of the two temperature gradients at the junction of a thermocouple. An arrangement has been built to explore this method. A precise value for the Peltier coefficient of a thermocouple has been obtained but which deviates from the Kelvin relation. A better design of the experimental device is needed.
Measurement of Thermopower and Current-Voltage Characteristics of Molecular Junctions to Identify Orbital Alignment
Tan, Aaron; Sadat, Seid; Reddy, Pramod
We report an experimental technique that concurrently measures the Seebeck coefficient and the current-voltage (I-V) characteristics of a molecular junction to determine the identity and the effective energetic separation of the molecular orbital closest to the electrodesÆ Fermi level. Junctions created by contacting a gold-coated atomic force microscope tip with a monolayer of molecules assembled on a gold substrate were found to have a Seebeck coefficient of (+16.9▒1.4) ?V/K. This positive value unambiguously shows that the highest occupied molecular orbital (HOMO) dominates charge transport. Further, by analyzing the (I-V) characteristics, the HOMO level is estimated to be ? 0.69?eV with respect to the Fermi level.
Thermoelectric properties of 50-nm-wide n- and p- type silicon nanowires
NASA Astrophysics Data System (ADS)
Kim, S. J.; Choi, W. C.; Zyung, T. H.; Jang, M. G.
For the evaluation of thermoelectric properties in silicon nanowires (SiNWs), thermoelectric test structures are manufactured, including 50-nm-wide n- and p-type SiNWs, micro-heater and temperature sensors using a conventional lithography method on 8 in. silicon wafer. For the optimization of thermoelectric properties in SiNWs, we have evaluated Seebeck coefficients and power factors of n- and p-type SiNWs by varying the nanowire length 10, 40 ?m and temperature (from 310 to 450 K). The results show that the maximum Seebeck coefficients and power factors are and for long p-type and long n-type SiNWs, respectively. The contribution of phonon-drag effect to thermoelectric power is discussed in the highly doped SiNWs.
Alloys Fabricated by Gas Atomization and Hot Extrusion
NASA Astrophysics Data System (ADS)
Madavali, Babu; Kim, Hyo-Seob; Hong, Soon-Jik
In this research, n-type (Bi2Te3)1- x (Bi2Se3) x -based thermoelectric (TE) materials were produced through a gas atomization process, and subsequently hot extruded with an extrusion ratio of 10:1 at 400 ░C. The effect of chemical composition on TE properties was investigated. The microstructure of all extruded bars showed a homogeneous and fine distribution of grains due to the dynamic recrystallization during the hot extrusion process. With increasing Bi2Te3 content, from 0.85 to 0.90, both electrical resistivity and Seebeck coefficient values were increased. The maximum figure of merit ( ZT) 0.673 was obtained at room temperature for (Bi2Te3)0.90(Bi2Se3)0.10 alloys due to them exhibiting higher seebeck coefficient and lower thermal conductivity than other compositions.
Metallic state and the metal-insulator transition of NdNiO3
NASA Astrophysics Data System (ADS)
Granados, X.; Fontcuberta, J.; Obradors, X.; Ma±osa, Ll.; Torrance, J. B.
We report detailed measurements of the electrical resistivity, Seebeck coefficient, and differential scanning calorimetry across the metal-insulator (MI) transition (TMI~=205 K) of NdNiO3. As in the isostructural oxide PrNiO3, the transition is extremely hysteretic, consistent with the first-order character of the transition. Analysis of the data shows that metallic and nonmetallic phases coexist in a broad temperature interval (~=70 K). The electrical resistivity and Seebeck coefficients of the metallic state display a clear linear temperature dependence. These properties can be rationalized in terms of a Fermi gas picture of rather heavy electrons (effective mass of about 6m0). Some physical parameters of the gas are predicted. The entropy change across the MI transition has been measured and it has been used to predict a strong pressure dependence of the MI transition temperature: dTMI/dP~=-4.8 K/kbar.
Structural and Thermoelectric Properties of Nanocrystalline Bismuth Telluride Thin Films Under Compressive and Tensile Strain
NASA Astrophysics Data System (ADS)
Kusagaya, K.; Hagino, H.; Tanaka, S.; Miyazaki, K.; Takashiri, M.
To investigate the effect of strain on bismuth telluride films, we applied different compressive and tensile strains to thin films by changing the bending radius of a flexible substrate so the strain ranged from -0.3% (compressive) to +0.3% (tensile). The structural properties of the strained thin films, composed of nanosized grains, were analyzed by x-ray diffraction and scanning electron microscopy. For all samples the main peak was the (015) diffraction peak; crystal orientation along the (015) growth direction was slightly enhanced by application of compressive strain. The thermoelectric properties of strained bismuth telluride thin films were evaluated by measurement of electrical conductivity, Seebeck coefficient, and power factor. The magnitude and direction of the applied strain did not significantly affect the power factor, because when the strain changed from compressive to tensile the electrical conductivity increased and the absolute Seebeck coefficient decreased.
High temperature transport properties of thermoelectric CaMnO{sub 3??} Ś Indication of strongly interacting small polarons
Schrade, M., E-mail: email@example.com; Finstad, T. G. [Centre for Materials Science and Nanotechnology, Department of Physics, University of Oslo, Sem Sµlandsvei 24, 0371 Oslo (Norway); Kabir, R.; Li, S. [School of Materials Science and Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia); Norby, T. [Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, FERMiO, Gaustadallķen 21, 0349 Oslo (Norway)
The conductivity and Seebeck coefficient of CaMnO{sub 3??} have been studied at temperatures up to 1000?░C and in atmospheres with controlled oxygen partial pressure. Both transport coefficients were varied in situ by the reversible formation of oxygen vacancies up to ??=?0.15. The charge carrier concentration was calculated using a defect chemical model. The Seebeck coefficient could be approximated by Heikes' formula, while the conductivity shows a maximum at a molar charge carrier concentration of 0.25. These results were interpreted as a signature of strong electronic correlation effects, and it was concluded that charge transport in CaMnO{sub 3??} occurs via strongly interacting small polarons. General prospects for strongly correlated materials as potential candidates for high temperature thermoelectric power generation were discussed.
High temperature transport properties of thermoelectric CaMnO3-? Ś Indication of strongly interacting small polarons
NASA Astrophysics Data System (ADS)
Schrade, M.; Kabir, R.; Li, S.; Norby, T.; Finstad, T. G.
The conductivity and Seebeck coefficient of CaMnO3-? have been studied at temperatures up to 1000 ░C and in atmospheres with controlled oxygen partial pressure. Both transport coefficients were varied in situ by the reversible formation of oxygen vacancies up to ? = 0.15. The charge carrier concentration was calculated using a defect chemical model. The Seebeck coefficient could be approximated by Heikes' formula, while the conductivity shows a maximum at a molar charge carrier concentration of 0.25. These results were interpreted as a signature of strong electronic correlation effects, and it was concluded that charge transport in CaMnO3-? occurs via strongly interacting small polarons. General prospects for strongly correlated materials as potential candidates for high temperature thermoelectric power generation were discussed.
Enhanced Thermoelectric Properties of Hole-Doped Lu1-x Pb x BaCo4O7 Ceramics
NASA Astrophysics Data System (ADS)
Chen, Y. B.; Cao, X. L.; Ma, R. X.; Gao, F.; Hu, X.; Song, H. Z.
The effects of Pb doping on the thermoelectric properties of Lu1-x Pb x BaCo4O7 (x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) ceramic samples prepared by the solid-state reaction method were investigated from 390 K to 973 K. The results show that Pb doping can reduce the electrical resistivity remarkably, increasing the Seebeck coefficient at lower temperatures and decreasing it at higher temperatures. As an overall result, Pb doping results in an enhancement of the power factor because the decrease in magnitude of the electrical resistivity is far greater than that of the Seebeck coefficient. The optimum Pb doping content is x = 0.08, reaching a power factor and ZT value of 85 ?W m-1 K-2 and 0.18, respectively, at 973 K.
Thermoelectricity of Nanocomposites Containing TiO2¢CoO Coaxial Nanocables
Su, L.; Zhang, L.; Gana, Y.X.
TiO{sub 2}-CoO coaxial nanocables were deposited into anodic aluminum oxide (AAO) nanoporous templates to form nanocomposite materials. Electron microscopic analysis was conducted to reveal their structures. Seebeck coefficients of the composites were measured. The highest absolute value of Seebeck coefficient is 393 {micro}V K{sup -1} for the TiO{sub 2} nanotube-filled AAO. The TiO{sub 2}-CoO coaxial nanocable-filled AAO has a lower absolute value of 300 {micro}V K{sup -1}. Both composites showed n-type behavior. The effect of Ag nanoparticles addition on the thermoelectric behavior was also examined.
Thin-film growth of the quasi-one-dimensional metal Li0.9Mo6O17
NASA Astrophysics Data System (ADS)
Cote, Alexandra; Moshfeghyeganeh, Saeed; Cohn, Joshua L.; Neumeier, John J.
Attempts to grow epitaxial thin films of Li0.9Mo6O17 by pulsed-laser deposition will be discussed. Single crystals of this quasi-one-dimensional (q1D) metal exhibit highly anisotropic Seebeck coefficients with ?S =Sc -Sb ~ 200 ? V/K near 450 K (the b axis corresponds to the most conducting, q1D chain direction). Suitably oriented thin films could enable possible applications in energy detection using the transverse Seebeck effect. X-ray diffraction results will be presented for films grown from a polycrystalline target on several substrates under a narrow range of temperature and pressure conditions. This material is based upon work supported by the U.S. Department of Energy Office of Basic Energy Sciences Grant DE-FG02-12ER46888 (Univ. Miami) and the National Science Foundation under Grant DMR-0907036 (Mont. St. Univ.)
Enhanced magnetocaloric effect material
Lewis, Laura J. H.
A magnetocaloric effect heterostructure having a core layer of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, and a constricting material layer coated on at least one surface of the magnetocaloric material core layer. The constricting material layer may enhance the magnetocaloric effect by restriction of volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect heterostructure powder comprising a plurality of core particles of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, wherein each of the core particles is encapsulated within a coating of a constricting material is also disclosed. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with a constricting material is disclosed.
Drivers for Control Effectiveness
Jan Pfister
\\u000a Internal control, as introduced in Sect. 2.1, represents the means to achieve organizational objectives. More specifically,\\u000a if internal control is effective, it provides reasonable assurance for the achievement of effective and efficient operations,\\u000a for reliable internal and external reporting, and for compliance with laws, regulations, and internal policies.1 Also, it has been clarified that in order to achieve control effectiveness,
NSDL National Science Digital Library
Russell Gersten
In this research brief the authors detail effective teaching strategies for teaching students with difficulties in math. The brief summarizes the work of over fifty research studies and details the practices that were seen as consistently effective across many of them. The brief details six instructional strategies and presents data describing the effectiveness of each on special education students and low-achieving students. The brief can be viewed on the webpage or downloaded as a PDF.
Mßximo, C E; Kaiser, R; Courteille, Ph W; Bachelard, R
We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease in magnetic field efficiency. PMID:25401364
Blowing Ratio Effects on Film Cooling EffectivenessĀ
Liu, Kuo-Chun
The research focuses on testing the film cooling effectiveness on a gas turbine blade suction side surface. The test is performed on a five bladed cascade with a blow down facility. Four different blowing ratios are used in this study, which are 0...
Effective Internships for Effective New Administrators.
ERIC Educational Resources Information Center
Edmonson, Stacey
One challenge faced by any educational leadership program is how to develop effective entry-level school administrators. Many administrative interns receive no real administrative practice at all through their internship, and yet upon completion of the internship, they are expected to be competent administrators. The internship at Sam Houstonģ
Cross-plane electrical and thermal transport in oxide metal/semiconductor superlattices
NASA Astrophysics Data System (ADS)
Jha, Pankaj
Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multiferroics, and thermoelectrics. Cross-plane electron filtering transport in metal/semiconductor superlattices provides a potential approach to increase the thermoelectric figure of merit (ZT). La0.67Sr0.33MnO3 (LSMO) and LaMnO3 (LMO) thin-film depositions were optimized using pulsed laser deposition (PLD) to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate (STO) substrates. X-ray diffraction and high-resolution reciprocal space mapping (RSM) indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively-coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal an effective barrier height of 220 meV. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 microV/K at 300K that increases to 16640 microV/K at 360K. The large Seebeck coefficient may arise due to hot electron and spin filtering as LSMO/LMO superlattice constituent materials exhibit spintronic properties where charges and spin current are intertwined and can generate a spin-Seebeck effect. The room temperature thermal conductivity achieved in low resistivity superlattices was 0.92 W/mK, which indicates that cross-plane phonon scattering at interfaces reduces the lattice contribution to the thermal conductivity. The giant contribution of spin-Seebeck, the large temperature dependence of the cross-plane power factor, and the low thermal conductivity in low resistance LSMO/LMO superlattices may offer opportunities to realize spin-magnetic thermoelectric devices, and suggests a direction for further investigations of the potential of LSMO/LMO oxide superlattices for thermoelectric devices.
NASA Technical Reports Server (NTRS)
Robock, Alan
Volcanic eruptions which inject large amounts of sulfur-rich gas into the stratosphere produce dust veils which last years and cool the earth's surface. At the same time, these dust veils absorb enough solar radiation to warm the stratosphere. Since these temperature changes at the earth's surface and in the stratosphere are both in the opposite direction of hypothesized effects from greenhouse gases, they act to delay and mask the detection of greenhouse effects on the climate system. Tantalizing recent research results have suggested regional effects of volcanic eruptions, including effects on El Nino/Southern Oscillation (ENSO). In addition, a large portion of the global climate change of the past 100 years may be due to the effects of volcanoes, but a definite answer is not yet clear. While effects of several years were demonstrated with both data studies and numerical models, long-term effects, while found in climate model calculations, await confirmation with more realistic models. Extremely large explosive prehistoric eruptions may have produced severe weather and climate effects, sometimes called a 'volcanic winter'. Complete understanding of the above effects of volcanoes is hampered by inadequacies of data sets on volcanic dust veils and on climate change. Space observations can play an increasingly important role in an observing program in the future. The effects of volcanoes are not adequately separated from ENSO events, and climate modeling of the effects of volcanoes is in its infancy. Specific suggestions are made for future work to improve the knowledge of this important component of the climate system.
Thermoelectric properties of quaternary Heusler alloys Fe2VAl1-xSix
NASA Astrophysics Data System (ADS)
Lue, C. S.; Chen, C. F.; Lin, J. Y.; Yu, Y. T.; Kuo, Y. K.
We report the effects of Si substitution on the temperature-dependent electrical resistivity, Seebeck coefficient, as well as thermal conductivity in the Heusler-type compound Fe2VAl . It is found that the substitution of Si onto the Al sites causes a significant decrease in the electrical resistivity and lattice thermal conductivity. A theoretical analysis indicated that the reduction of lattice thermal conductivity arises mainly from point-defect scattering of the phonons. With slight substitution, the Seebeck coefficient changes sign from positive to negative, accompanied by the appearance of a broad minimum at high temperatures. These features are associated with the change in the electronic band structure, where the Fermi level shifts upwards from the center of the pseudogap due to electron-doping effect. For x>0.1 in Fe2VAl1-xSix , no broad minimum in the Seebeck coefficient appears, indicative of a dramatic modification in the band structure of these materials. While the thermoelectric performance improves with increasing Si concentration, the largest figure-of-merit ZT value among these alloys is still an order of magnitude lower than conventional thermoelectric materials.
Preparation of Bi2Te3/Nano-SiC Composite Thermoelectric Films by Electrodeposition
NASA Astrophysics Data System (ADS)
Wang, Yilin; Zhang, Jingyi; Shen, Zhengwu; Yang, Mengqian; Liu, Xiaoqing; Wang, Wei
Bi2Te3/nano-SiC composite thermoelectric films were prepared by electrodeposition in a nitric acid bath. The effects of SiC concentration and annealing treatment on the Seebeck coefficient and electrical resistivity of the films were investigated. The morphology, composition, and structure of the films were studied by scanning electron microscopy, x-ray fluorescence spectroscopy, and x-ray diffraction. The results showed that SiC nano-particles in electrodeposited Bi2Te3/nano-SiC composite films have readily apparent effects on the crystal orientation of the Bi2Te3 matrix and the morphology of the electrodeposited composite films. For nano-SiC particle concentrations <2 g/L the Seebeck coefficients of as-deposited films decrease with increasing nano-SiC particle concentration and decrease further after annealing treatment. Improvement in electrical conductivity compensated for the decrease in Seebeck coefficient and resulted in an enhanced power factor. Addition of nano-SiC particles to the composite films introduces more interfaces, which endows the composite films with lower electrical resistivity.
ERIC Educational Resources Information Center
Layne, L.
The author looks at the meaning of specific terminology commonly used in student surveys: "effective teaching." The research seeks to determine if there is a difference in how "effective teaching" is defined by those taking student surveys and those interpreting the results. To investigate this difference, a sample group of professors and studentsģ
Relativistic effects in chemistry
K. B. Yatsimirskii
Relativistic effects become apparent when the velocity of the electron is arbitrarily close to the speed of light (137 au) without actually attaining it (in heavy atoms of elements at the end of Mendeleev's Periodic Table). At the orbital level, the relativistic effect is apparent in the radial contraction of penetrating s and p shells, expansion of nonpenetrating d and
Robert Karplus; J. M. Luttinger
Both the unusually large magnitude and strong temperature dependence of the extraordinary Hall effect in ferromagnetic materials can be understood as effects of the spin-orbit interaction of polarized conduction electrons. It is shown that the interband matrix elements of the applied electric potential energy combine with the spin-orbit perturbation to give a current perpendicular to both the field and the
NSDL National Science Digital Library
Reich, Hans J.
Hans Reich, professor of organic chemistry at the University of Wisconsin Madison, created this online handout on named rules and effects in organic chemistry. Concise descriptions and structures of a number of named effects, rules, stereochemical models and hypothesesŌ??from BaldwinŌ??s rules to the ZimmermanŌ??Traxler transition stateŌ??are given.
ERIC Educational Resources Information Center
da Silva, J. J. R. Frausto
Discusses ambiguities of the accepted definition of the chelate effect, suggesting that it be defined in terms of experimental observation rather than mathematical abstraction. Indicates that the effect depends on free energy change in reaction, ligand basicity, pH of medium, type of chelates formed, and concentration of ligands in solution. (JN)
[Providing Effective Behavior Support.
ERIC Educational Resources Information Center
SAIL: Technical Assistance Journal, 1996
This theme issue addresses the provision of behavioral support for students with behavior disorders. The first article, "Providing Effective Behavior Support to All Students: Procedures and Processes" (George Sugai), summarizes the literature on the effectiveness of various interventions and offers several models for examining the teaching ofģ
The aid effectiveness literature
Hristos Doucouliagos; Supmartin Paldam
Abstract: The AEL consists of empirical macro studies of the effects of development aid. At the end of 2004 it had reached 97 studies of three families, which we have summarized in one study each using meta-analysis. Studies of the effect on investments show that they rise by ,\\/3 ofthe aid ¢ the rest is crowded out by a fall
ERIC Educational Resources Information Center
Bedard, Catherine; Belin, Pascal
Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consistedģ
Resumming the Effective Action
A. Leonidov; A. Zelnikov
At the simple example of a massless scalar field propagating in the static background we study the resummed expressions for the effective action at zero and finite temperature that are free from a usual sickness of the effective action induced by massless particles.
Differential school effectiveness
Studies of school effectiveness are briefly reviewed. pointing to the need to study effectiveness for sub-groups within each school as well as overall. The results of a multilevel analysis of a large dataset covering the years 1985. 1986 and 1987 and using examination performance as the outcome measure are presented, revealing substantial differences between ethnic groups. The findings also show
Fry, R.J.M.
As more people spend more time in space, and the return to the moon and exploratory missions are considered, the risks require continuing examination. The effects of microgravity and radiation are two potential risks in space. These risks increase with increasing mission duration. This document considers the risk of radiation effects in space workers and explorers. 17 refs., 1 fig., 4 tabs.
Earthquake Effects and Experiences
NSDL National Science Digital Library
This portion of the United States Geological Survey's (USGS) frequently-asked-questions feature on earthquakes addresses what individuals might actually experience during an earthquake. Topics include earthquake motion (rolling or shaking), earthquake effects (ground shaking, surface faulting, ground failure, etc.), earthquake magnitude, what an earthquake feels like, and others. There are also links to additional resources on earthquake effects and experiences.
Listen to this page Effects of Drug Abuse Drug abuse hurts the people who take drugs AND the people around them, including families , kids , and ... HIV/AIDS Click here to learn more about effects of specific drugs . VIDEO: Why Are Drugs So ...
Cardiovascular Effects Of Weightlessness
NASA Technical Reports Server (NTRS)
Sandler, Harold
NASA technical memorandum presents study of effects of weightlessness and simulations upon cardiovascular systems of humans and animals. Reviews research up to year 1987 in United States and Soviet space programs on such topics as physiological changes induced by weightlessness in outer space and by subsequent return to Earth gravity and also reviews deconditioning effects of prolonged bed rest on ground.
Carbon star effective temperatures
S. T. Ridgway; G. H. Jacoby; R. R. Joyce; D. C. Wells
Possible methods for measuring the effective temperatures of individual carbon stars are discussed. Since calibrations of broad or narrow-band photometric colors is impractical at present, empirical corrections to narrow band color temperatures is the only valid procedure. The effective temperature of the star TW Oph is estimated, based on preliminary reduction of the occultation and associated photometry
The effect of temperature on thermoelectric properties of n-type Bi2Te3 nanowire/graphene layer-by-layer hybrid composites.
Ju, Hyun; Kim, Jooheon
The thermoelectric properties of Bi2Te3 nanowire/graphene composites prepared at different sintering temperatures have been investigated. The as-synthesized ultrathin Bi2Te3 nanowires are uniformly distributed between the graphene layers, leading to the formation of Bi2Te3 nanowire/graphene layer-by-layer hybrid structures. The electrical conductivity of the as-sintered composites increases dramatically with the sintering temperature, as the relative density and grain size increase and the interface density decreases. This in turn lowers the Seebeck coefficient due to the reduction of the potential barrier for carriers and their scattering at the interface. The fabricated n-type Bi2Te3 nanowire/graphene composites exhibit an enhanced figure of merit of 0.25 at an optimal sintering temperature of 623 K. PMID:26050633
NASA Astrophysics Data System (ADS)
Schwarz, John H.
It is conjectured that the world-volume action of a probe D3-brane in an AdS 5 ū S 5 background of type IIB superstring theory, with one unit of flux, can be reinterpreted as the exact effective action (or highly effective action) for U(2) = 4 super Yang-Mills theory on the Coulomb branch. An analogous conjecture for U(2) k ū U(2)- k ABJM theory is also presented. The main evidence supporting these conjectures is that the brane actions have all of the expected symmetries and dualities. Highly effective actions have general coordinate invariance, even though they describe nongravitational theories.
NSDL National Science Digital Library
This page was authored by the CATALST Group at the University of Minnesota, based on an original activity by Richard Lesh at Purdue University.
This model-eliciting activity challenges students to operationally define a construct (study effectiveness). Students are given a survey to review that rates different aspects of study behaviors. They are then given a set of data for a few students and asked to use their scores to determine an index of study effectiveness. After determining a method, they are then asked to use this index to put five students in rank order according to their scores on study effectiveness. Students write a report explaining the method they used to determine these scores and how they produced their ratings.
Thermoelectric power factor enhancement with gate-all-around silicon nanowires
Curtin, Benjamin M., E-mail: firstname.lastname@example.com [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Bowers, John E. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States)
The thermoelectric properties of gate-all-around silicon nanowires (Si NWs) are calculated to determine the potential for significant power factor enhancement. The Boltzmann transport equation and relaxation time approximation are employed to develop an electron transport model used to determine the field-effect mobility, electrical conductivity, Seebeck coefficient, and power factor for Si NWs with cross-sectional areas between 4?nm?ū?4?nm and 12?nm?ū?12?nm and a range of gate biases. Electrical conductivity for the gated Si NWs was much higher than that of doped Si due to the lack of ionized impurities and correspondingly greater carrier mobility. A significant increase in electrical conductivity with decreasing Si NW cross-sectional area was also observed due to a large increase in the average carrier density. For all Si NWs, the Seebeck coefficient was lower than that of doped bulk Si due to the different energy dependence between ionized impurity and phonon-mediated scattering processes. This decrease was also confirmed with Seebeck coefficient measurements of multigated Si NWs and n-type Si thin-films. Quantum confinement was also found to increase the Seebeck coefficient for <8?nm?ū?8?nm Si NWs and also at high charge densities. A maximum power factor of 6.8?ū?10{sup ?3}?W m{sup ?1} K{sup ?2} was calculated for the 6?nm?ū?6?nm Si NWs with typical Si/SiO{sub 2} interface roughness, which is 2¢3?ū?those obtained experimentally for bulk Si. The power factor was also found to greatly depend on surface roughness, with a root-mean-square roughness of <0.8?nm necessary for power factor enhancement. An increase in ZT may also be possible if a low thermal conductivity can be obtained with minimal surface roughness.
The Manhattan Effect 1 Running Head: THE MANHATTAN EFFECT
Reber, Paul J.
The Manhattan Effect 1 Running Head: THE MANHATTAN EFFECT The Manhattan Effect: When Relationship Wilhelm Hofmann University of Cologne Date: November 20, 2013 #12;The Manhattan Effect 2 Abstract Research in such situations is termed the Manhattan effect. These findings suggest that the partner
Relative Effect Declarations for Lightweight Effect-Polymorphism
Diggavi, Suhas
by the effect annotation e, the effect of a polymorphic function consists of two parts: the concrete effect e might have the topmost effect . However, in the concrete invocation expression f ((x: A) x), we see effects is closely related to the work on anchored ex- ceptions [2]. We break up their connection between
Creating effective character animationĀ
Gerwig, Jennifer
Several stages are involved in the creation of an graphics. effective, three-dimensional character animation. Before starting any work at the computer, the animator should consider what his characters will look like and how they will move, as well...
Strategies for Effective Outsourcing.
ERIC Educational Resources Information Center
Moneta, Larry; Dillon, William L.
Emphasizes strategies that can be employed for effective outsourcing in higher education settings. Several models of outsourcing are identified and described, and examples of institutions using each model are provided. (GCP)
NSDL National Science Digital Library
Mark Abolins
This PowerPoint show depicts the effects (blast, heat, etc.) of the Chesapeake Bay impact. To emphasize the human consequences of asteroid and comet impacts, the slides show what would happen to East Coast communities if an identical object hit the same place today. (The impact actually happened roughly 35 million years ago.) Impact effects were estimated with the Earth Impact Effects Program (www.lpl.arizona.edu/impacteffects/). Effects shown on these slides are at best very approximate, and, consequently, these slides should only be used to stimulate discussions about impact hazards. Satellite images were obtained through the NASA Earth Observing System Higher Education Alliance (GeoBrain) which provided funding for this work. Graphics were created with the Environmental Systems Research Institute (ESRI) family of geographic information system (GIS) products.
Effectiveness Safety Committee
Farritor, Shane
Increase the Effectiveness of Your Safety Committee Lisa Tobiason An equal opportunity educator 302 Acres. Ł East Campus 338 Acres. #12;UNL Safety Committees Ę Chancellors University Safety Committee (CUSC). Ę Unit Safety Committees. Ł Thirty-two active committees representing Lincoln campuses
PROCUREMENT ~ Effective and efficient
Duchowski, Andrew T.
PROCUREMENT SERVICES ~ Effective and efficient procurement of quality products and services at the best value from reputable vendors ~ Disbursements Division ~ Committed to providing quality financial, advisory, and administrative support to the University and supplier communities ~ Welcome to your directory
Identifying Effective School Principals
Fernandez, Kandyce; Flores, Santa; Huang, Emily; Igwe, Carolyn; McDonald, Leslie; Stroud, Ryan; Willis, Rebecca; Dugat, Amber
that teacher retention is also associated with principal effectiveness. Dissatisfaction with administrative support is frequently highly ranked as one of the reasons teachers leave a school (Graziano 2005; Ingersoll 2001; Darling-Hammond 1997). Results...
Ototoxic Medications (Medication Effects)
Ototoxic Medications (Medication Effects) By Barbara Cone, Patricia Dorn, Dawn Konrad-Martin, Jennifer Lister, Candice Ortiz, and ... in our Audiology Information Series [PDF]. What Is Ototoxicity? Certain medications can damage the ear, resulting in ...
Cytogenetic effects of cyclamates
Jemison, E.W.; Brown, K.; Rivers, B.; Knight, R.
PHA-stimulated human peripheral lymphocytes were used as a model system for assessing the in vitro effects of calcium cyclamate. Techniques of autoradiography, cytological staining, cell counting, liquid scintillation and karyotyping were used to study the cytogenetic damage and biochemical effects of calcium cyclamate when assayed in 24 hour intervals for 96 hours. The cells were exposed to 10(-2) and 10(-3) molar concentrations of calcium cyclamate in TC 199 medium with fetal calf serum and antibiotics. It was noted that the addition of cyclamate increased mitotic rate of lymphocyte cells in cultures. It was determined that calcium cyclamate impaired the synthesis of deoxribonunucleic acid (as depicted by decreased incorporation of tritiated thymidine), reduced grain counts in autoradiographs and increased chromosome aberrations in cyclamate treated PHA stimulated peripheral blood lymphocytes in vitro. Morphological changes and growth rates showed significant effects. These studies indicate that calcium cyclamate has variable significant effects on leucocytes growth and chromosome morphology.
Azoulay, Pierre
In a market context, a status effect occurs when actors are accorded differential recognition for their efforts depending on their location in a status ordering, holding constant the quality of these efforts. In practice, ...
Kaptchuk, Ted J; Miller, Franklin G
Research has revealed placebo effects to be genuine biopsychosocial phenomena representing more than simply spontaneous remission or normal symptom fluctuations. How can this understanding be used to benefit patients? PMID:26132938
Deposition and investigation of lanthanum-cerium hexaboride thin films
Kuzanyan, A.S. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia)]. E-mail: firstname.lastname@example.com; Harutyunyan, S.R. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Vardanyan, V.O. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Badalyan, G.R. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Petrosyan, V.A. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Kuzanyan, V.S. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Petrosyan, S.I. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Karapetyan, V.E. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Wood, K.S. [NRL, Washington, DC 20375 (United States); Wu, H.-D. [SFA/NRL, Washington, DC 20375 (United States); Gulian, A.M. [Physics Art Frontiers/NRL, Washington, DC 20375 (United States)
Thin films of lanthanum-cerium hexaboride, the promising thermoelectric material for low-temperature applications, are deposited on various substrates by the electron-beam evaporation, pulsed laser deposition and magnetron sputtering. The influence of the deposition conditions on the films X-ray characteristics, composition, microstructure and physical properties, such as the resistivity and Seebeck coefficient, is studied. The preferred (100) orientation of all films is obtained from XRD traces. In the range of 780-800 deg. C deposition temperature the highest intensity of diffractions peaks and the highest degree of the preferred orientation are observed. The temperature dependence of the resistivity and the Seebeck coefficient of films are investigated in the temperature range of 4-300 K. The features appropriate to Kondo effect in the dependences {rho}(T) and S(T) are detected at temperatures below 20 K. Interplay between the value of the Seebeck coefficient, metallic parameters and Kondo scattering of investigated films is discussed. - Graphical abstract: Kondo scattering in (La,Ce)B{sub 6} films: temperature dependence of the resistivity of (La,Ce)B{sub 6} films on various substrates and the ceramics La{sub 0.99}Ce{sub 0.01}B{sub 6}.
Codoping in SnTe: Enhancement of Thermoelectric Performance through Synergy of Resonance Levels and Band Convergence.
Tan, Gangjian; Shi, Fengyuan; Hao, Shiqiang; Chi, Hang; Zhao, Li-Dong; Uher, Ctirad; Wolverton, Chris; Dravid, Vinayak P; Kanatzidis, Mercouri G
We report a significant enhancement of the thermoelectric performance of p-type SnTe over a broad temperature plateau with a peak ZT value of ?1.4 at 923 K through In/Cd codoping and a CdS nanostructuring approach. Indium and cadmium play different but complementary roles in modifying the valence band structure of SnTe. Specifically, In-doping introduces resonant levels inside the valence bands, leading to a considerably improved Seebeck coefficient at low temperature. Cd-doping, however, increases the Seebeck coefficient of SnTe remarkably in the mid- to high-temperature region via a convergence of the light and heavy hole bands and an enlargement of the band gap. Combining the two dopants in SnTe yields enhanced Seebeck coefficient and power factor over a wide temperature range due to the synergy of resonance levels and valence band convergence, as demonstrated by the Pisarenko plot and supported by first-principles band structure calculations. Moreover, these codoped samples can be hierarchically structured on all scales (atomic point defects by doping, nanoscale precipitations by CdS nanostructuring, and mesoscale grains by SPS treatment) to achieve highly effective phonon scattering leading to strongly reduced thermal conductivities. In addition to the high maximum ZT the resultant large average ZT of ?0.8 between 300 and 923 K makes SnTe an attractive p-type material for high-temperature thermoelectric power generation. PMID:25856499
Thermoelectric Properties of Double-Filled p-Type La1- z Yb z Fe4- x Co x Sb12 Skutterudites
NASA Astrophysics Data System (ADS)
Joo, Gyeong-Seok; Shin, Dong-Kil; Kim, Il-Ho
La and Yb double-filled p-type skutterudites (La1- z Yb z Fe4- x Co x Sb12; 0.25 ? z ? 0.75 and 0.5 ? x ? 1) were synthesized by encapsulated melting and homogenized by use of heat treatment. It was apparent from the positive signs of the Seebeck coefficient and the Hall coefficient that all specimens had p-type characteristics. The carrier concentration decreased with charge compensation. The thermal conductivity and the electrical conductivity decreased and the Seebeck coefficient increased with increasing substitution of Co for Fe. However, the carrier concentration was increased by increasing the Yb filling ratio. Electrical conductivity increased and the Seebeck coefficient decreased with increasing Yb filling, because the electron valence of Yb2+ was lower than that of La3+. The thermal conductivity decreased with charge compensation, and the lattice thermal conductivity decreased with increasing Yb filling. Yb was more effective than La at reducing lattice thermal conductivity. The power factor ( PF) and dimensionless figure of merit ( ZT) increased with increasing temperature up to a specific temperature. The maximum PF = 2.81 mW/mK2 at 823 K was obtained for La0.75Yb0.25Fe3.5Co0.5Sb12 and the maximum ZT = 0.74 at 723 K was achieved for La0.5Yb0.5Fe3CoSb12.
Brain effects of melanocortins
Alfio Bertolini; Raffaella Tacchi; Anna Valeria Vergoni
The melanocortins (?, ? and ?-melanocyte-stimulating hormones: MSHs; adrenocorticotrophic hormone: ACTH), a family of pro-opiomelanocortin (POMC)-derived peptides having in common the tetrapeptide sequence His-Phe-Arg-Trp, have progressively revealed an incredibly wide range of extra-hormonal effects, so to become one of the most promising source of innovative drugs for many, important and widespread pathological conditions.The discovery of their effects on some brain
NSDL National Science Digital Library
Learners conduct a simple experiment to model and explore the harmful effects of acid rain (vinegar) on living (green leaf and eggshell) and non-living (paper clip) objects. Learners observe the effects over a period of days. This activity has links to other activities which can be combined to make a larger lesson. Resource contains vocabulary definitions and suggestions for assessment, extensions, and scaling for different levels of learners.
Effects of periodic discharges
NASA Technical Reports Server (NTRS)
Ford, F. E.
Periodic capacity checks are assessed as well as the effects of periodic discharges on the cycle life and the performance of cells during the cycle life. Topics discussed include the effect of the amount of electrolyte on cell capacity at 35 C; battery design for spacecraft; electrolyte starvation theory; battery separator degradation; negative electrode stability; voltage regulation; operating temperatures; and integration of reconditioning systems using microprocessors.
Tcherniega, N V
We observed new effect which we called photonic flame effect (PFE). Several 3-dimensional photonic crystals (artificial opals) were posed on Cu plate at the temperature of liquid nitrogen (77K). Typical distance between them was 1-5 centimeters. Long-continued optical luminescence was excited in one of them by the ruby laser pulse. Analogous visible luminescence manifesting time delay appeared in other samples of the crystals. Experiments were realized for opal crystals and for nanocomposites (opals filled with nonlinear liquids).
[Antinociceptive effects of counterirritants].
Taniguchi, Y; Deguchi, Y; Saita, M; Noda, K
Counterirritants such as l-menthol, methyl salicylate, camphor, thymol and capsaicin are widely used in the treatment of mild pains and itches by topical application. However, little experimental research on counterirritants has been reported. In the present study, we investigated the antinociceptive effects and mechanisms of topically applied counterirritants, especially those of l-menthol. From the formalin test in mice, l-menthol (at a concentration of 1-30% in ethanol) showed a major effect in the early phase of pain response (0-5 min). In contrast, the antinociceptive effects of indomethacin (10 mg/kg, p.o.) were found only in the late phase of pain response (15-25 min). Furthermore, morphine (0.75-6 mg/kg, s.c.) dose-dependently inhibited both phases. l-Menthol-induced analgesia during the early phase was significantly blocked by naloxone and potentiated by bestatin. The antinociceptive effects of l-menthol were furthermore examined in dexamethasone-treated mice. l-Menthol also produced antinociceptive effects in the hot plate test of mice and hind paw pressure test of rats. l-Menthol showed mild surface and infiltrating anesthetic effects in guinea pigs. l-Menthol did not inhibit both carrageenin-induced paw edema of rats and the synthesis of prostaglandin E2 in vitro. Based on these findings, we proposed that l-menthol produces antinociceptive effects by activation of the endogenous opioid system and/or partially by local anesthetic actions without anti-inflammatory effects. PMID:7851817
Pleiotropic effects of pitavastatin
Davignon, Jean
3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are established first line treatments for hypercholesterolaemia. In addition to the direct effects of statins in reducing concentrations of atherogenic low density lipoprotein cholesterol (LDL-C), several studies have indicated that the beneficial effects of statins may be due to some of their cholesterol-independent, multiple (pleiotropic) effects which may differ between different members of the class. Pitavastatin is a novel synthetic lipophilic statin that has a number of pharmacodynamic and pharmacokinetic properties distinct from those of other statins, which may underlie its potential pleiotropic benefits in reducing cardiovascular risk factors. This review examines the principal pleiotropic effects of pitavastatin on endothelial function, vascular inflammation, oxidative stress and thrombosis. The article is based on a systematic literature search carried out in December 2010, together with more recent relevant publications where appropriate. The available data from clinical trials and in vitro and animal studies suggest that pitavastatin is not only effective in reducing LDL-C and triglycerides, but also has a range of other effects. These include increasing high density lipoprotein cholesterol, decreasing markers of platelet activation, improving cardiac, renal and endothelial function, and reducing endothelial stress, lipoprotein oxidation and, ultimately, improving the signs and symptoms of atherosclerosis. It is concluded that the diverse pleiotropic actions of pitavastatin may contribute to reducing cardiovascular morbidity and mortality beyond that achieved through LDL-C reduction. PMID:22053916
Barner, J.O.; Cunningham, M.E.; Freshley, M.D.; Lanning, D.D.
This is the final report of the High Burnup Effects Program (HBEP). It has been prepared to present a summary, with conclusions, of the HBEP. The HBEP was an international, group-sponsored research program managed by Battelle, Pacific Northwest Laboratories (BNW). The principal objective of the HBEP was to obtain well-characterized data related to fission gas release (FGR) for light water reactor (LWR) fuel irradiated to high burnup levels. The HBEP was organized into three tasks as follows: Task 1 -- high burnup effects evaluations; Task 2 -- fission gas sampling; and Task 3 -- parameter effects study. During the course of the HBEP, a program that extended over 10 years, 82 fuel rods from a variety of sources were characterized, irradiated, and then examined in detail after irradiation. The study of fission gas release at high burnup levels was the principal objective of the program and it may be concluded that no significant enhancement of fission gas release at high burnup levels was observed for the examined rods. The rim effect, an as yet unquantified contributor to athermal fission gas release, was concluded to be the one truly high-burnup effect. Though burnup enhancement of fission gas release was observed to be low, a full understanding of the rim region and rim effect has not yet emerged and this may be a potential area of further research. 25 refs., 23 figs., 4 tabs.
Effect lines for specifying animation effects Yoshikazu Kato, Etsuya Shibayama
Takahashi, Shin
in comics and cartoons. They depict information on the effects of an object, such as its speed, length animation effects by drawing effect lines. Ef- fect lines are a popular technique that is used in comics
Anomalous Skin Effect Igor Kaganovich
Kaganovich, Igor
Anomalous Skin Effect Revisited Igor Kaganovich Princeton Plasma Physics Laboratory #12 to explain "simply" anomalous skin effect without abusing physics. #12;3 Outline Skin effect (Inductively Coupled Plasmas/ Lasers) Ł Normal skin effect Ł Concept of phase-mixing and scale Ł Anomalous skin effect
Effects of double filling of La and Ce on thermoelectric properties of Ce{sub m}La{sub n}Fe{sub 1.0}Co{sub 3.0}Sb{sub 12} compounds by spark plasma sintering
Lu, Q.M.; Zhang, J.X.; Zhang, X.; Liu, Y.Q.; Liu, D.M.; Zhou, M.L. [Key Laboratory of Advanced Functional Materials, Ministry of Education, College of Material Science and Engineering, Beijing University of Technology, Beijing 100022 (China)
Double-filled skutterudite compounds Ce{sub m}La{sub n}FeCo{sub 3}Sb{sub 12} with (m+n)=0.2-0.4 were synthesized by spark plasma sintering using powders of Co, Sb, Fe, and rare-earth Ce and La as starting materials, and the thermoelectric properties were studied in detail. The dominant phases of all the samples are the skutterudite with small amount of Sb as an impurity phase, and the amount of Sb decreases in double-filled compound. The lattice constant is enhanced linearly up to (m+n)=0.30 with increasing filling fraction and then unchanged. The Seebeck coefficient and thermal conductivity of double-filled compounds are generally higher than single-filled samples whatever the filling fraction is. Among all the samples, Ce{sub 0.1}La{sub 0.2}FeCo{sub 3}Sb{sub 12} shows the highest Seebeck coefficient of 150 {mu}V K{sup -1} at 773 K and the lowest thermal conductivity of 1.81 W/mK at 673 K, and the maximum ZT value reaches 0.60 at 773 K due to its lower thermal conductivity.
Effects of acemannan on macrophagesĀ
Zhang, Linna
, immune stimulation, anticancer, and antiviral effects. It is unclear how acemannan exerts this wide variety of effects. One common cell, however, that appears to link all the biological effects of acemannan is the macrophage. Macrophages play a wide...
Effects of acemannan on macrophages
Zhang, Linna
, immune stimulation, anticancer, and antiviral effects. It is unclear how acemannan exerts this wide variety of effects. One common cell, however, that appears to link all the biological effects of acemannan is the macrophage. Macrophages play a wide...
Stormwater BMP Effectiveness Assessment Toolkit
US EPA has identified stormwater BMP effectiveness as a priority research need. Effective protection of biotic integrity requires that processes maintaining the diversity of physical habitats be protected. Methods are needed to evaluate the effectiveness of existing Stormwater ...
The Generation Effect and Memory
Rosner, Zachary Alexander
generation effect: Further tests of the lexical activation hypothesis.generation effect: Some tests of the lexical activation hypothesis.generation effect for item memory was the cognitive effort hypothesis (
Rf radiation: biological effects
Lerner, E.J.
The controversy surrounding the biological effects and health hazards of radio-frequency (RF) radiation (below the infrared frequency of 300 gHz) is examined. The average person is exposed to only extremely low levels of RF radiation. However, a substantial fraction of the population receives higher than average exposures because of increased use of microwave ovens and citizens band radios. Possible effects of exposure to RF radiation on brain function are investigated. Results of limited studies of long-term low-level effects are presented. The question of legal liability concerning exposure of the general public to RF radiation generated by microwave ovens and FM antennas is explored. (4 diagrams, 4 graphs, 1 table)
Wunderlich, J÷rg; Park, Byong-Guk; Irvine, Andrew C; ZŌrbo, Liviu P; Rozkotovß, Eva; Nemec, Petr; Novßk, VĒt; Sinova, Jairo; Jungwirth, Tomßs
The field of semiconductor spintronics explores spin-related quantum relativistic phenomena in solid-state systems. Spin transistors and spin Hall effects have been two separate leading directions of research in this field. We have combined the two directions by realizing an all-semiconductor spin Hall effect transistor. The device uses diffusive transport and operates without electrical current in the active part of the transistor. We demonstrate a spin AND logic function in a semiconductor channel with two gates. Our study shows the utility of the spin Hall effect in a microelectronic device geometry, realizes the spin transistor with electrical detection directly along the gated semiconductor channel, and provides an experimental tool for exploring spin Hall and spin precession phenomena in an electrically tunable semiconductor layer. PMID:21205664
Effective Nutritional Supplement Combinations
NASA Astrophysics Data System (ADS)
Cooke, Matt; Cribb, Paul J.
Few supplement combinations that are marketed to athletes are supported by scientific evidence of their effectiveness. Quite often, under the rigor of scientific investigation, the patented combination fails to provide any greater benefit than a group given the active (generic) ingredient. The focus of this chapter is supplement combinations and dosing strategies that are effective at promoting an acute physiological response that may improve/enhance exercise performance or influence chronic adaptations desired from training. In recent years, there has been a particular focus on two nutritional ergogenic aidsŚcreatine monohydrate and protein/amino acidsŚin combination with specific nutrients in an effort to augment or add to their already established independent ergogenic effects. These combinations and others are discussed in this chapter.
NASA Technical Reports Server (NTRS)
Sleboda, Claire
Quality assurance programs provide a very effective means to monitor and evaluate medical care. Quality assurance involves: (1) Identify a problem; (2) Determine the source and nature of the problem; (3) Develop policies and methods to effect improvement; (4) Implement those polices; (5) Monitor the methods applied; and (6) Evaluate their effectiveness. Because this definition of quality assurance so closely resembles the Nursing Process, the health unit staff was able to use their knowledge of the nursing process to develop many forms which improve the quality of patient care. These forms include the NASA DFRC Service Report, the occupational injury form (Incident Report), the patient survey (Pre-hospital Evaluation/Care Report), the Laboratory Log Sheet, the 911 Run Sheet, and the Patient Assessment Stamp. Examples and steps which are followed to generate these reports are described.
Giant thermoelectric effect in graphene-based topological insulators with heavy adatoms and nanopores.
Chang, Po-Hao; Bahramy, Mohammad Saeed; Nagaosa, Naoto; Nikoli?, Branislav K
Designing thermoelectric materials with high figure of merit ZT = S(2)GT/Ktot requires fulfilling three often irreconcilable conditions, that is, the high electrical conductance G, small thermal conductance Ktot, and high Seebeck coefficient S. Nanostructuring is one of the promising ways to achieve this goal as it can substantially suppress lattice contribution to Ktot. However, it may also unfavorably influence the electronic transport in an uncontrollable way. Here, we theoretically demonstrate that this issue can be ideally solved by fabricating graphene nanoribbons with heavy adatoms and nanopores. The adatoms locally enhance spin-orbit coupling in graphene thereby converting it into a two-dimensional topological insulator with a band gap in the bulk and robust helical edge states, which carry electrical current and generate a highly optimized power factor S(2)G per helical conducting channel due to narrow boxcar-function-shaped electronic transmission (surpassing even the Mahan-Sofo limit obtained for delta-function-shaped electronic transmission). Concurrently, the array of nanopores impedes the lattice thermal conduction through the bulk. Using quantum transport simulations coupled with first-principles electronic and phononic band structure calculations, the thermoelectric figure of merit is found to reach its maximum ZT ? 3 at low temperatures T ? 40 K. This paves a way to design high-ZT materials by exploiting the nontrivial topology of electronic states through nanostructuring. PMID:24932511
Side Effects of Hormone Therapy
... My Bridge 4 Life Clinical Trials Guides Newsletters Nutrition & Wellness PCF Spotlight Glossary African American Men Living with Prostate Cancer Side Effects of Hormone Therapy Side Effects Urinary ...
US Army Corps of Engineers public web site for the "Environmental Residue Effects Database", a searchable database of adverse biological effects associated with tissue concentrations of various contaminants....
Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.
NASA Technical Reports Server (NTRS)
The in-situ optical surface measurement system is a facility designed to study the deleterious effects of particulate materials on the surface reflectivities of optical materials in the vacuum ultraviolet (VUV). This arrangement is designed to simulate the on-orbit effects of contamination and degradation of optical surfaces. This simulation is accomplished through the use of non-coherent VUV sources illuminating optical surfaces located in a high vacuum chamber. Several sources of contamination are employed. The reflectivity is measured both at the specular reflection as well as at two scattered positions, forward and reverse. The system components are described and an operating procedure is given.
Effects and effect inference for a core Java calculus
Gavin M. Bierman; Matthew J. Parkinson
An effects system can be used to delimit the scope of computational effects within a program. This information is not only useful for the programmer, but also can be used in the definition of a number of optimizations. Most effects systems have been defined for functional languages with simple state. Greenhouse and Boyland have recently suggested how an effects system
Effective Nonverbal Communication.
ERIC Educational Resources Information Center
Parratt, Smitty
Discusses the importance of understanding nonverbal communication in enhancing the personal and work relationships of interpreters and increasing their effectiveness in meeting the needs of customers. Discusses the mystique of body language, cultural variation in the use of gestures, the stages of an encounter, interpreting gesture clusters, andģ
Visualization and Effective Instruction.
ERIC Educational Resources Information Center
Moonen, Jef
Reviews the potential relationship between visualization and effective instruction. Highlights include the use of graphical user interfaces for enhancing visual communication, integrating visual communication into courseware design, theoretical principles of visual communication, empirical research needs, AIME (amount of invested mental effort),ģ
Repetition Effects in Grasping
Peter Dixon; Scott McAnsh; Lenore Read
The task in the present experiments was to reach out and grasp a novel object that afforded two possible grips. Different versions of the object were created that biased subjects to use one grip or the other. The dependent variable was the repetition effect, the tendency to repeat the grip that was used on the previous trial. In Experiment 1,
Towards Hall effect spintronics
A. Gerber
Major efforts in the current exploration of spintronics are focused on the giant magnetoresistance (GMR) phenomenon in metallic, semiconducting and tunnel junction magnetic heterostructures. I wish to present a different approach based on the extraordinary Hall effect (EHE). Since its discovery more than a century ago, the EHE was not considered seriously for technological applications because of its relatively small
Gary White; Tony Mondragon; David Slaughter; Dorothy Coates
Two models for demonstrating tides and experimenting with various tidal effects are presented. The first takes advantage of the approximately inverse-square nature of the force law for magnetic poles and exhibits symmetric tidal bulges on opposite sides of the planet, analogous to the tides of the earth. The second demonstration apparatus is a realization of the ``rubber sheet'' geometry analogy
Biasing Effects of Experimenters.
ERIC Educational Resources Information Center
Rosenthal, Robert
Explains the types of effects, usually unintentional, that psychologists can have upon the results of their research; describes the "Pygmalion Experiment," in which teachers' expectations for children's behavior proved to be self-fulfilling prophecies; and points to research needs in the area of interpersonal expectations. (GT)
M. J. Colles; N. R. Geddes; E. Mehdizadeh
The generation of acoustic signals following optical absorption in gases and solids is described. Important parameters in the design of cells and their relationships to detection sensitivity and limiting noise signals are discussed. Examples are given of important applications of the optoacoustic effect in pollution monitoring, the measurement of lifetimes and gas-phase and solid state spectroscopy.
Bob Kane; John Crawford; David Grant
In this study, scales were developed to measure the extent to which organisations exhibited ōsoftö or ōhardö approaches to HRM, and the extent to which potential barriers to the effective operation of HRM were present. The sample comprised 549 employees, managers and HRM staff across a wide range of types of organisations in Australia, New Zealand, the USA, the UK
NSDL National Science Digital Library
Jeff Radel
This website presents an online tutorial about creating effective poster presentations. The site guides users through the basics of poster design, which should free the presenter to focus on discussion of essential elements of the work. Decisions about poster format and design which contribute to efficient and accurate transfer of information using this medium are also discussed.
ERIC Educational Resources Information Center
Male, Mary
The Student Study Team (SST) is described as a California intervention model that encourages effective multidisciplinary team participation. The development, training, operation, and evaluation of such teams are discussed, and implementation recommendations are offered. The article includes a flow chart of the SST process, a meeting competencyģ
Teacher Effectiveness: A Position.
ERIC Educational Resources Information Center
Scott, Myrtle
This document summarizes the highlights of research on teacher effectiveness and concludes with recommendations based on a synthesis of this past work. The various methodologies that have been used are discussed, from rating scales to objective observation techniques, such as OScAR and the ecological studies. The major problems in teacherģ
Mohammad Taghi Goodarzi; Mohammad Reza Safari; Fatemeh Zal
Background: Combination of glycation and oxidation is associated with diabetes mellitus. The aim of this study was to clarify the effect of glycated proteins in presence of transition metal ions on production of reactive oxygen species (ROS) in rat hepatocyte suspension. Methods: Glycated albumin was prepared by incubation of bovine serum albumin with 100 mM glucose in 0.3 M phosphate
Robert E. Slavin
This article reviews evaluations of IBM's Writing to Read program in kindergartens and first grades. In Writing to Read (WTR), students rotate through five learning stations to learn and practice phonics, to write stories, and to listen to recorded books. Two of these stations involve computers. Twenty-one studies of Writing to Read in kindergartens found a median effect size of
Technology Transfer Automated Retrieval System (TEKTRAN)
Effective integrated pest management programs are needed for food processing and storage facilities and this requires improvements in our ability to monitor pest populations and use this information to target management tactics in both time and space. The use of pheromone traps to detect pests is i...
Climatic Effects of Urbanization
T. M. Barzyk; J. E. Frederick
Urban areas around the world have been increasing in size and population density in recent decades. The United Nations reports that in 1900, urbanites comprised 14% of the world's population. This value has increased to 47% in the year 2000, and is expected to grow to 60% by 2030. The goal of this study is to isolate the effects of
Peter H. G. Berkhout; Jos C. Muskens; Jan W. Velthuijsen
This paper gives rigorous definitions of the rebound effect, not only in the well described single commodity case (Khazzoom, 1980. The Energy Journal 1(4), 21¢40.), but also for a multiple commodity case. It is shown that the familiar laws for the single case do not hold for the multiple case. The paper describes the state of the art of empirical
The EPA's OHMSETT facility has developed a rapid field test that includes some of the theoretical aspects and conditions of dispersion at sea. This Field Dispersant Effectiveness Test (FDET) has been used to evaluate the dispersibility of various commonly-transported oils and mak...
E. Fortunato; Nuno Correia; Pedro Barquinha; Clßudia Costa; LuĒs Pereira; Gonńalo Gonńalves; Rodrigo Martins
In this paper we report the use of a sheet of cellulose fiber-based paper as the dielectric layer used in oxide based semiconductor thin film field-effect transistors (FETs). In this new approach we are using the cellulose fiber-based paper in an \\
Developing Effective Tourism Leadership
Karin Weber; Adele Ladkin
This study explores the development of effective leadership in the tourism industry from the perspective of current industry leaders in Hong Kong, China. The literature reviews the key themes in tourism leadership research, which is followed by an empirical qualitative study of 10 leaders in the tourism industry in Hong Kong. Findings are explored in relation to three key areas:
M. Kroner; A. O. Govorov; S. Remi; B. Biedermann; S. Seidl; A. Badolato; P. M. Petroff; W. Zhang; R. Barbour; B. D. Gerardot; R. J. Warburton; K. Karrai
The Fano effect is ubiquitous in the spectroscopy of, for instance, atoms, bulk solids and semiconductor heterostructures. It arises when quantum interference takes place between two competing optical pathways, one connecting the energy ground state and an excited discrete state, the other connecting the ground state with a continuum of energy states. The nature of the interference changes rapidly as
NSDL National Science Digital Library
This portal provides links to information on the potential damage caused to the environment by acid rain. An introductory paragraph briefly describes the damage to lakes and streams, building materials, and monuments. Each link access additional information on these topics: surface waters and aquatic animals, forests, automotive coatings, soluble building materials such as marble or limestone, atmospheric haze, and human health effects.
S. L. Ruby; L. M. Epstein; K. H. Sun
Because ferrooyanide has no magnetic moment, it was investigated as an ; absorber in studies of the Mossbaner effect with FeŌüĄŌüĘ as source. The ; source was soft iron plated with CoŌüĄŌüĘ and annealed; the 14.4-kev gamma ray ; from the vibrated source was passed through a sodium ferrocyanide absorber at 80 ; and 300 deg K and then analyzed.
Rainfall Effects Acknowledgements
Reduced AirflowInfiltration front Displaced vapor plume Dissolved plume as source Stable, open atmosphere Effects The intrusion of contaminated vapor originating from groundwater plumes and source zones this knowledge gap, an experimental and modeling study was initiated at the Colorado School of Mines to determine
Improving Glove Barrier Effectiveness
Dietmar Rabussay; Denise M. Korniewicz
Perioperative staff members depend on surgical gloves to prevent disease transmission between themselves and patients, but these gloves frequently fail during use. Three approaches can make surgical gloves more effective barriers: preventing glove failures, monitoring glove integrity, and improving glove quality. Failure prevention includes modifying surgical techniques, improving instruments and equipment, streamlining teamwork, selecting the most appropriate gloves, double gloving,
The Negative Repetition Effect
ERIC Educational Resources Information Center
Mulligan, Neil W.; Peterson, Daniel J.
A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, andģ
ERIC Educational Resources Information Center
Phillips, Gary W.
In 1987, a survey report by J. Cannell was published criticizing state reports based on national standardized testing of elementary school students that indicated that all 50 states were above the national average. This phenomenon--known as the "Lake Wobegon Effect"--is analyzed. Technical problems with the study are considered. (TJH)
Documentation: Effective AND Literate
Paul S. Burdett Jr.
The purpose of this paper is to show how documentation can be literate, in a stylistic sense, and still be effective. Literate prose is a powerful tool that, when properly used in computer documentation, can take advantage of the full power of the English language. This does not mean that all computer documentation must or can read like a Nobel
Lorenz Attractor -- Butterfly Effect
NSDL National Science Digital Library
Dr. Michael Cross, Cal Tech
The "Butterfly Effect", or more technically the "sensitive dependence on initial conditions", is the essence of chaos. This is illustrated an applet of the Lorenz Attractor. The demonstration shows a graphical representation of the time variation of three variables X(t),Y(t) and Z(t), coupled by non-linear evolution equations.
NSDL National Science Digital Library
This lesson plan will help students learn to evaluate energy-related purchases in terms of cost-effectiveness. How long will it take for the new purchase to "pay for itself" in terms of energy savings? The lesson involves both sustainability and economics concepts. The lesson should take two or three class periods to complete.
NASA Technical Reports Server (NTRS)
Wickman, Jerry L.; Kundu, Nikhil K.
This laboratory exercise seeks to develop a cost effective prototype development. The exercise has the potential of linking part design, CAD, mold development, quality control, metrology, mold flow, materials testing, fixture design, automation, limited parts production and other issues as related to plastics manufacturing.
Effectively Communicating Qualitative Research
ERIC Educational Resources Information Center
Ponterotto, Joseph G.; Grieger, Ingrid
This article is a guide for counseling researchers wishing to communicate the methods and results of their qualitative research to varied audiences. The authors posit that the first step in effectively communicating qualitative research is the development of strong qualitative research skills. To this end, the authors review a process model forģ
... EFFECT 5 = EXTREMELY)SUGGESTIONS FOR COPING Lack of energy/ I Change time of day medication fatigue/ sleepiness is taken. I Exercise. I Change diet. Dry mouth I Drink water. I Take care of teeth and mouth. Weight gain I Eat low fat foods. I Reduce food portions. I Avoid junk food. ...
Reporting Research Results Effectively
ERIC Educational Resources Information Center
Volkwein, J. Fredericks
Assessment research is at its best when it packages research results and data so that they can be digested by multiple audiences. Too many assessment researchers spend all their efforts planning and executing the research project with little attention to closing the loop at the end. If assessment findings are not communicated effectively, theģ
The biological effects of manganese were studied in a town on the coast of Dalmatia in which a ferromanganese plant has been operating since before World War II. The study focused on the question of whether the exposure to manganese can cause a higher incidence of respiratory dis...
Environmental Effects on Advanced Materials
NASA Astrophysics Data System (ADS)
Jones, R. H.; Henager, C. H.; Trzaskoma, Patricia P.; Stoloff, N. S.; Moffat, T. P.; Lichter, B. D.
This in-depth overview examines a number of key considerations relating to environmental effects on today's advanced materials. While certainly not inclusive of all environmental issues, the article does investigate high-temperature corrosion and crack growth in ceramics and ceramic composites, hydrogen effects on ceramics, hydrogen effects on fracture of intermetallics, and corrosion and hydroen effects in amorphous or glassy metals.
Thermoelectric energy conversion The objective of this laboratory is for you to explore the physics and practical aspects of solidsate heat
Braun, Paul
. Session 2: Seebeck coefficient and thermoelectric power generation Ę Measure the Seebeck coefficientThermoelectric energy conversion Objective The objective of this laboratory is for you to explore energy using thermoelectric materials, and the thermodynamic limits to the efficiency of heat
Verbal response-effect compatibility
Iring Koch; Wilfried Kunde
Ideomotor theory states that motor responses are activated by an anticipation of their sensory effects. We assumed that anticipated\\u000a effects would produce response-effect (R-E) compatibility when there is dimensional overlap of effects and responses. In a\\u000a four-choice task, visual digit stimuli called for verbal responses (color names). Each response produced a written response-effect\\u000a on the screen. In different groups, the
Limited list: limited effects?
Taylor, R J; Bond, C M
During the first month after the limited National Health Service drug list came into effect 17 cooperative general practitioners recorded the actions taken when a now prohibited drug would formerly have been prescribed. An average of 6% of direct surgery contacts with patients and 8% of indirect contacts with patients were affected by the new regulations, but in 2% and 4% of cases respectively the patient received the same pharmacological substance under a different (generic or approved) name. Where a real change in pharmacological constitution or formulation had been required four fifths of these substitutes were considered by the doctors to result in less effective treatment. In 1% of contacts no drug was issued or recommended where one would formerly have been given. PMID:3928035
Safety Intervention Effectiveness
Judging safety intervention effectiveness is often left up to the eye of the beholder. Safety and Health Professionals must increase skills and increase their body of knowledge, based on scientific evidence, that can be applied confidently in the workplace. Evidence must be collected and analyzed to separate the interventions of the month with those that stand the test of time. The book Guide to Evaluating the Effectiveness of Strategies for Preventing Work injuries DHHS (NIOSH) Publication No. 2001-119, April 2001, serves as a primary reference. An example study related to biorhythms, popular in the late 1970s, is used to illustrate the separating of scientific evidence and pseudo-science hype. The cited biorhythm study focuses on the relationship of the accident dates and the three biorhythmic cycles (physical, emotional, and intelligence).
NASA Astrophysics Data System (ADS)
Tong, Wei
Piezomagnetism designates a change in the magnetization of materials induced by mechanical actions such as tension or compression. The type of Barkhausen effect that occurs in this work consists of sudden, discontinuous jumps in a material's magnetization that appear in response to smooth (continuous) stress variations. A series of strain controlled fatigue tests with an alternating sinusoidal waveform were carried out to study the relationship between the endurance limit and the Barkhausen effect. Results of fatigue tests on steel specimens exhibiting Barkhausen pulses at various stages are reported and a threshold-crossing analysis is applied to the test results. These studies show that when the fatigue limit is approached, the Barkhausen pulses become, in general, more intense in amplitude and quantity than at other stress levels. A hypothetical mechanism is proposed that relates the intensity of the Barkhausen response to the inception of micro-cracking and rearrangements of the mechanical lattice at the microscopic level.
Cardiac effects of thyronamines.
Zucchi, Riccardo; Ghelardoni, Sandra; Chiellini, Grazia
3-Iodothyronamine (T(1)AM) is an endogenous compound derived from thyroid hormone through decarboxylation and deiodination, which interacts with a novel G protein-coupled receptor, known as trace amine-associated receptor 1 (TAAR1). TAAR1 and other receptors of this family are expressed in several tissues, including the heart. Functional effects have been observed after administration of exogenous T(1)AM: in the isolated heart, a negative inotropic and chronotropic action was produced, and the resistance to ischemic injury was increased, possibly as a consequence of an action on intracellular calcium homeostasis. Extracardiac effects include reduction of body temperature, increased lipid versus carbohydrate metabolism, and modulation of insulin secretion. T(1)AM might play an important physiological or pathophysiological role, and this signaling system might allow the development of new therapeutical agents. PMID:19016324
Electrocardiographic effects of rivastigmine.
Morganroth, Joel; Graham, Stephen; Hartman, Richard; Anand, Ravi
The electrocardiographic (ECG) effects of rivastigmine treatment were assessed in mild to moderately severe Alzheimer's disease (AD) by analysis of four 26-week, double-blind, multicenter, placebo-controlled, phase III clinical trials. Of an initial 2791 patients, 77% completed treatment. Seventy-one percent required at least one concomitant medication for conditions other than AD, with 34% requiring cardiovascular medications. Safety assessments included ECGs, adverse events, vital signs, and clinical laboratory parameters. Pooled 12-lead ECG data were analyzed by an independent cardiologist blinded to treatment group and clinical information. Heart rate, PR, QRS, and QTc intervals did not differ significantly between treatment and placebo groups. Percentage change from baseline for PR, QRS, and QTc intervals was also no different. In conclusion, rivastigmine appears not to produce adverse effects on cardiac function assessed by ECG. PMID:12017350
Towards Hall effect spintronics
NASA Astrophysics Data System (ADS)
Gerber, A.
Major efforts in the current exploration of spintronics are focused on the giant magnetoresistance (GMR) phenomenon in metallic, semiconducting and tunnel junction magnetic heterostructures. I wish to present a different approach based on the extraordinary Hall effect (EHE). Since its discovery more than a century ago, the EHE was not considered seriously for technological applications because of its relatively small value in bulk magnetic materials. Several techniques were recently developed to significantly enhance the effect. Field sensitivity of tens to hundreds ?/T has been obtained. We argue that EHE-based sensors and memory devices promise a number of valuable advantages, including high sensitivity, thermal stability and simplicity and low cost manufacture, and can become an alternative to the GMR.
Bliokh, Konstantin Y; Nori, Franco
We consider the relativistic deformation of quantum waves and mechanical bodies carrying intrinsic angular momentum (AM). When observed in a moving reference frame, the centroid of the object undergoes an AM-dependent transverse shift. This is the relativistic analogue of the spin-Hall effect, which occurs in free space without any external fields. Remarkably, the shifts of the geometric and energy centroids differ by a factor of 2, and both centroids are crucial for the Lorentz transformations of the AM tensor. We examine manifestations of the relativistic Hall effect in quantum vortices and mechanical flywheels and also discuss various fundamental aspects of this phenomenon. The perfect agreement of quantum and relativistic approaches allows applications at strikingly different scales, from elementary spinning particles, through classical light, to rotating black holes. PMID:22540559
Konstantin Y. Bliokh; Franco Nori
We consider the relativistic deformation of quantum waves and mechanical bodies carrying intrinsic angular momentum (AM). When observed in a moving reference frame, the centroid of the object undergoes an AM-dependent transverse shift. This is the relativistic analogue of the spin Hall effect, which occurs in free space without any external fields. Remarkably, the shifts of the geometric and energy centroids differ by a factor of 2, and both centroids are crucial for the correct Lorentz transformations of the AM tensor. We examine manifestations of the relativistic Hall effect in quantum vortices, and mechanical flywheels, and also discuss various fundamental aspects of this phenomenon. The perfect agreement of quantum and relativistic approaches allows applications at strikingly different scales: from elementary spinning particles, through classical light, to rotating black-holes.
NASA Astrophysics Data System (ADS)
Bliokh, Konstantin Y.; Nori, Franco
We consider the relativistic deformation of quantum waves and mechanical bodies carrying intrinsic angular momentum (AM). When observed in a moving reference frame, the centroid of the object undergoes an AM-dependent transverse shift. This is the relativistic analogue of the spin-Hall effect, which occurs in free space without any external fields. Remarkably, the shifts of the geometric and energy centroids differ by a factor of 2, and both centroids are crucial for the Lorentz transformations of the AM tensor. We examine manifestations of the relativistic Hall effect in quantum vortices and mechanical flywheels and also discuss various fundamental aspects of this phenomenon. The perfect agreement of quantum and relativistic approaches allows applications at strikingly different scales, from elementary spinning particles, through classical light, to rotating black holes.
Interpersonal effectiveness trainingĀ
DeOtte, Dona Lou Lewis
, Shoulders & Fair, 1974; Zlegler & Mazen, 1975). Johnson (1972) has suggested a combination of techniques, includ- ing insight, behavior training and transactional analysis, to help clients learn more effective methods of living together. Such a com..., 1975; Stuart, 1969; Weiss et al. , 1972; Wieman et al. , 1974; Ziegler & Mazen, 1975). The contingency contract is a means of circumventing the initial phase of resistance in couples where dys- functional patterns of relating are firmly established...
NSDL National Science Digital Library
The objective of this Web site is twofold: (1) to describe the Hall measurement technique for determining the carrier density and mobility in semiconductor materials and (2) to initiate an electronic interaction forum where workers interested in the Hall effect can exchange ideas and information. It includes an introductory description of the Hall measurement technique and covers basic principles, equipment, and recommended procedures. Keywords: Conductance, conductivity, resistance, resistivity
Magnetic effects on thermocouples
NASA Astrophysics Data System (ADS)
BeguÜ, Samo; Bojkovski, Jovan; DrnovÜek, Janko; GerÜak, Gregor
Thermometers in laboratory environment and industrial applications are often subject to extraneous, usually unwanted and uncontrolled magnetic fields. Magnetic field influence can be minimized, but cannot be fully cancelled out. Even more, in most cases, there is no awareness of the existence of magnetic fields, let alone their effect on measurement instrumentation. In the past, sensitivity to high dc magnetic fields has been investigated in cryogenics and at high temperatures. More recently, the magnetic effect on weak dc magnetic fields was presented. The goal of this paper was to analyse and empirically and experimentally prove the magnetic sensitivity of thermocouples exposed to low magnetic fields: both dc and ac. Precision and uniform alternating and direct magnetic flux densities were generated by means of permanent magnets and power amplifiers with air-cored coils. The magnetic effect on ferromagnetic and non-ferromagnetic thermocouples at liquid-nitrogen-boiling point (-196 ░C), ice point (0 ░C), in water (17 ░C) and at melting point of gallium fixed point cell (29.7646 ░C) was investigated. Magnetic-field-dependent temperature errors of up to 700 mK (at 5.3 mT: dc) and up to 1 ░C (at 10 mT: ac 50 Hz magnetic fields) were detected. From the results, it can be concluded that, ideally for temperature measurements of the highest accuracy in the above-cryogenic temperature range, magnetic sensitivity should be estimated and taken into account either as the correction of an error and/or as an additional source of measurement uncertainty. Special consideration should be given to thermocouple orientation relative to the magnetic field direction, influence of metal enclosures and magnetization effects on ferromagnetic components of thermocouples.
NSDL National Science Digital Library
This 8-page monograph offers strategies for effective questioning that engages students and that deepens their conceptual understanding in mathematics. It suggests questions and prompts that help students progress through various stages of the problem solving process and that help teachers assess the thinking of students. The article describes the purposes of questions at different stages of a lesson and describes situations when it is appropriate to convey information to students. A list of references is included.
Cardiac effects of thyronamines
Riccardo Zucchi; Sandra Ghelardoni; Grazia Chiellini
3-Iodothyronamine (T1AM) is an endogenous compound derived from thyroid hormone through decarboxylation and deiodination, which interacts with\\u000a a novel G protein-coupled receptor, known as trace amine-associated receptor 1 (TAAR1). TAAR1 and other receptors of this\\u000a family are expressed in several tissues, including the heart. Functional effects have been observed after administration of\\u000a exogenous T1AM: in the isolated heart, a negative
Brian Diffey; Colin Hindson; F Lawlor
A study was made of adverse dermatological reactions to the non-steroidal anti-inflammatory agent benoxaprofen. Photosensitivity was seen in several patients, confined to wavelengths less than 340 nm. Other cutaneous side effects were erythema multiforme, the Stevens-Johnson syndrome, milia, and onycholysis. One case of pancytopenia and toxic epidermal necrolysis was reported. patients were not rechallenged with the drug, but these reactions
NSDL National Science Digital Library
Created by Illuminations: Resources for Teaching Mathematics, this lesson is designed to help students understand the significance of outliers. This lesson includes thought questions and an applet to help students visualize the effect of an outlier. The authors divide the lesson into different groups, they include: learning objectives, materials, instructional plans, NCTM standards/expectations, and finally references. This is a great interactive resource for those wanting to learn more about correlation and regression.
NASA Astrophysics Data System (ADS)
Binder, J. M.; Landig, A. J.
The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for secondary school students. This is our solution to problem number 10, The Kaye effect, as presented in the final round of the 21st IYPT in Trogir, Croatia. The Kaye effect occurs when a thin stream of shampoo or a different adequate non-Newtonian liquid is poured onto a surface. Suddenly, a jet leaves the heap that is formed by the shampoo and begins to 'dance' around the primary jet like a lasso. The phenomenon ends when the 'dancing' jet hits the primary jet and subsequently collapses. We started our investigations based on available literature (Kaye 1963 Nature 197 1001, Versluis et al 2006 J. Stat. Mech., Collyer and Fischer 1976 Nature 261 682). We made experiments with a similar experimental set-up in which we could determine the velocities of both shampoo streams as well as the angle of the 'dancing' stream. From there on, we developed a theoretical model for the energy loss of the jet in the heap. We discovered that the air layer between the jet and the heap is a necessity for the Kaye effect to occur. At this point, our observations differ from the aforementioned literature. This also accounts for the shampoo beam acting as a light guide. Further experiments concerning the viscoelasticity of the shampoo revealed that the elastic property of the shampoo is necessary for the effect to occur. This article is a written version of the oral contribution of the German team to the 21st IYPT competition, which was awarded first prize by an international jury. The article has been edited by European Journal of Physics.
NASA Technical Reports Server (NTRS)
Direct and indirect effects of lightning on aircraft were examined in relation to aircraft design. Specific trends in design leading to more frequent lightning strikes were individually investigated. These trends included the increasing use of miniaturized, solid state components in aircraft electronics and electric power systems. A second trend studied was the increasing use of reinforced plastics and other nonconducting materials in place of aluminum skins, a practice that reduces the electromagnetic shielding furnished by a conductive skin.
Cascading Effects Following Intervention
Patterson, Gerald R.; Forgatch, Marion S.; DeGarmo, David S.
Four different sources for cascade effects were examined using 9-year process and outcome data from a randomized controlled trial (RCT) of a preventive intervention using Parent Management Training ¢ Oregon Model (PMTOÖ). The social interaction learning (SIL) model of child antisocial behavior serves as one basis for predicting change. A second source addresses the issue of comorbid relationships among clinical diagnoses. The third source, collateral changes, describes events in which changes in one family member correlate with changes in another. The fourth component is based on the long-term effects of reducing coercion and increasing positive interpersonal processes within the family. New findings from the 9-year follow-up show that mothers experienced benefits as measured by standard of living (i.e., income, occupation, education, and financial stress) and frequency of police arrests. It is assumed that PMTO reduces the level of coercion, which sets the stage for a massive increase in positive social interaction. In effect, PMTO alters the family environment and thereby opens doors to healthy new social environments. PMID:20883592
Bachiocco, Valeria; Mondardini, Maria Cristina
Placebo analgesia is the occurrence of an analgesic drug effect without drugs. The response is learned through conditioning and mediated by expectancy. It lies on the up-regulation of the pain-modulating areas and the down-regulation of the pain-encoding regions. A further mechanism is the retrieval of the brain circuit activity previously excited by drugs. We describe the case of an infant affected by a tracheal agenesis who underwent a series of operative and diagnostic bronchoscopies for which she received midazolam and fentanyl. After 61 procedures the infant showed a somatosensory response which in our interpretation reflected a placebo effect. Ontogenetic considerations and specific observations indicate that the infant had the appropriate competences in her learning and memory systems and nociceptive and antinociceptive circuits for the placebo effect to take place. Generalizing, the introduction of placebo manipulation in infant pain management may be taken into consideration; its approach through observational and experimental studies is the preliminary target. PMID:20705216
Neuroprotective effects of Asiaticoside
Qi, Feng-yan; Yang, Le; Tian, Zhen; Zhao, Ming-gao; Liu, Shui-bing; An, Jia-ze
In the central nervous system, Asiaticoside has been shown to attenuate in vitro neuronal damage caused by exposure to ?-amyloid. In vivo studies demonstrated that Asiaticoside could attenuate neurobehavioral, neurochemical and histological changes in transient focal middle cerebral artery occlusion animals. In addition, Asiaticoside showed anxiolytic effects in acute and chronic stress animals. However, its potential neuroprotective properties in glutamate-induced excitotoxicity have not been fully studied. We investigated the neuroprotective effects of Asiaticoside in primary cultured mouse cortical neurons exposed to glutamate-induced excitotoxicity invoked by N-methyl-D-aspartate. Pretreatment with Asiaticoside decreased neuronal cell loss in a concentration-dependent manner and restored changes in expression of apoptotic-related proteins Bcl-2 and Bax. Asiaticoside pretreatment also attenuated the upregulation of NR2B expression, a subunit of N-methyl-D-aspartate receptors, but did not affect expression of NR2A subunits. Additionally, in cultured neurons, Asiaticoside significantly inhibited Ca2+ influx induced by N-methyl-D-aspartate. These experimental findings provide preliminary evidence that during excitotoxicity induced by N-methyl-D-aspartate exposure in cultured cortical neurons, the neuroprotective effects of Asiaticoside are mediated through inhibition of calcium influx. Aside from its anti-oxidant activity, down-regulation of NR2B-containing N-methyl-D-aspartate receptors may be one of the underlying mechanisms in Asiaticoside neuroprotection. PMID:25221579
Environmental effects of aluminium.
Rosseland, B O; Eldhuset, T D; Staurnes, M
Aluminium (Al), when present in high concentrations, has for long been recognised as a toxic agent to aquatic freshwater organisms,i.e. downstream industrial point sources of Al-rich process water. Today the environmental effects of aluminium are mainly a result of acidic precipitation; acidification of catchments leads to increased Al- concentrations in soil solution and freshwaters. Large parts of both the aquatic and terrestrial ecosystems are affected.In the aquatic environment, aluminium acts as a toxic agent on gill-breathing animals such as fish and invertebrates, by causing loss of plasma- and haemolymph ions leading to osmoregulatory failure. In fish, the inorganic (labile) monomeric species of aluminium reduce the activities of gill enzymes important in the active uptake of ions. Aluminium seems also to accumulate in freshwater invertebrates. Dietary organically complexed aluminium, maybe in synergistic effects with other contaminants, may easily be absorbed and interfere with important metabolic processes in mammals and birds.The mycorrhiza and fine root systems of terrestrial plants are adversely affected by high levels of inorganic monomeric aluminium. As in the animals, aluminium seems to have its primary effect on enzyme systems important for the uptake of nutrients. Aluminium can accumulate in plants. Aluminium contaminated invertebrates and plants might thus be a link for aluminium to enter into terrestrial food chains. PMID:24202562
Effective mass in quantum effects of radiation pressure
M. Pinard; Y. Hadjar; A. Heidmann
We study the quantum effects of radiation pressure in a high-finesse cavity with a mirror coated on a mechanical resonator. We show that the optomechanical coupling can be described by an effective susceptibility which takes into account every acoustic modes of the resonator and their coupling to the light. At low frequency this effective response is similar to a harmonic response with an effective mass smaller than the total mass of the mirror. For a plano-convex resonator the effective mass is related to the light spot size and becomes very small for small optical waists, thus enhancing the quantum effects of optomechanical coupling.
Effective Learning and Effective Learners: Behavioral and Neuroimaging Studies
Loudon, Catherine
Effective Learning and Effective Learners: Behavioral and Neuroimaging of subsequent learning opportunities-- a phenomenon known as test-potentiated learning. This phenomenon will be explored in a series of experiments that use behavioral
Effect Size and Moderators of Effects for Token Economy InterventionsĀ
Soares, Denise
EFFECT SIZE AND MODERATORS OF EFFECTS FOR TOKEN ECONOMY INTERVENTIONS A Dissertation by DENISE A. SOARES Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... EFFECT SIZE AND MODERATORS OF EFFECTS FOR TOKEN ECONOMY INTERVENTIONS A Dissertation by DENISE A. SOARES Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR...
Sergei Kuksin; Alberto Maiocchi
In this chapter we present a general method of constructing the effective equation which describes the behaviour of small-amplitude solutions for a nonlinear PDE in finite volume, provided that the linear part of the equation is a hamiltonian system with a pure imaginary discrete spectrum. The effective equation is obtained by retaining only the resonant terms of the nonlinearity (which may be hamiltonian, or may be not); the assertion that it describes the limiting behaviour of small-amplitude solutions is a rigorous mathematical theorem. In particular, the method applies to the three-- and four--wave systems. We demonstrate that different possible types of energy transport are covered by this method, depending on whether the set of resonances splits into finite clusters (this happens, e.g. in case of the Charney-Hasegawa-Mima equation), or is connected (this happens, e.g. in the case of the NLS equation if the space-dimension is at least two). For equations of the first type the energy transition to high frequencies does not hold, while for equations of the second type it may take place. In the case of the NLS equation we use next some heuristic approximation from the arsenal of wave turbulence to show that under the iterated limit "the volume goes to infinity", taken after the limit "the amplitude of oscillations goes to zero", the energy spectrum of solutions for the effective equation is described by a Zakharov-type kinetic equation. Evoking the Zakharov ansatz we show that stationary in time and homogeneous in space solutions for the latter equation have a power law form. Our method applies to various weakly nonlinear wave systems, appearing in plasma, meteorology and oceanology.
Presser, T.S.
Hypothesized to be derived from Cretaceous marine sedimentary rocks, selenium contamination of the Kesterson National Wildlife Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway of selenium is defined here as the 'Kesterson effect.' At the refuge ponds, this effect culminated in 1983 in a 64% rate of deformity and death of embryos and hatchlings of wild aquatic birds. From the previous companion paper on irrigation drainage, the Kesterson effect has been implicated in nine of 11 reconnaissance areas studied in the western United States. Deformities have resulted in at least five of these sites. Climatic, geologic, hydrologic, and soil conditions in these reconnaissance areas are similar to those in the area surrounding Kesterson National Wildlife Refuge in the west-central San Joaquin Valley of California, in California, selenium as selenate, was ultimately found weathered with sulfur from marine sources in soluble sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California Coast Ranges were deposited. Bioaccumulation may be therefore a primary mechanism of selenium enrichment in ancient sediments in addition to that of the formerly suggested Cretaceous volcanic pathway.
Markus Roellig
Almost all properties of a photodissociation region (PDR) depend on its metallicity. The heating and cooling efficiencies that determine the temperature of the gas and dust, the dust composition, as well as the elemental abundances that influence the chemical structure of the PDR are just three examples that demonstrate the importance of metallicity effects in PDRs. PDRs are often associated with sites of star formation. If we want to understand the star formation history of our own Galaxy and of distant low-metallicity objects we need to understanding how metallicity acts on PDR physics and chemistry.
NSDL National Science Digital Library
Carol McLaren
This site provides an overview of the Earth's atmospheric greenhouse effect by briefly exploring the atmospheres of nearby planets and discussing the greenhouse gases of our atmosphere, such as, water vapor, carbon dioxide, methane, ozone, and nitrous oxide. Students will learn that the heat-trapping ability of a greenhouse is influenced by a number of factors, including the transparency of the greenhouse cover, and color and texture of the planet's surfaces. This site serves as a resource for and includes links to two classroom activities.
Assuring reliability program effectiveness.
NASA Technical Reports Server (NTRS)
Ball, L. W.
An attempt is made to provide simple identification and description of techniques that have proved to be most useful either in developing a new product or in improving reliability of an established product. The first reliability task is obtaining and organizing parts failure rate data. Other tasks are parts screening, tabulation of general failure rates, preventive maintenance, prediction of new product reliability, and statistical demonstration of achieved reliability. Five principal tasks for improving reliability involve the physics of failure research, derating of internal stresses, control of external stresses, functional redundancy, and failure effects control. A final task is the training and motivation of reliability specialist engineers.
NSDL National Science Digital Library
The Concord Consortium
Transistors are the building blocks of modern electronic devices. Your cell phones, iPods, and computers all depend on them to operate. Thanks to today's microfabrication technology, transistors can be made very tiny and be massively produced. You are probably using billions of them while working with this activity now--as of 2006, a dual-core Intel microprocessor contains 1.7 billion transistors. The field effect transistor is the most common type of transistor. So we will focus on it in this activity.
Assessments of astronaut effectiveness
NASA Technical Reports Server (NTRS)
Rose, Robert M.; Helmreich, Robert L.; Fogg, Louis; Mcfadden, Terry J.
This study examined the reliability and convergent validity of three methods of peer and supervisory ratings of the effectiveness of individual NASA astronauts and their relationships with flight assignments. These two techniques were found to be reliable and relatively convergent. Seniority and a peer-rated Performance and Competence factor proved to be most closely associated with flight assignments, while supervisor ratings and a peer-rated Group Living and Personality factor were found to be unrelated. Results have implications for the selection and training of astronauts.
Hepatoprotective effects of mushrooms.
Soares, Andrķia Assunńo; de Sß-Nakanishi, Anacharis Babeto; Bracht, Adelar; da Costa, Sandra Maria Gomes; Koehnlein, Eloß Angķlica; de Souza, Cristina Giatti Marques; Peralta, Rosane Marina
The particular characteristics of growth and development of mushrooms in nature result in the accumulation of a variety of secondary metabolites such as phenolic compounds, terpenes and steroids and essential cell wall components such as polysaccharides, b-glucans and proteins, several of them with biological activities. The present article outlines and discusses the available information about the protective effects of mushroom extracts against liver damage induced by exogenous compounds. Among mushrooms, Ganoderma lucidum is indubitably the most widely studied species. In this review, however, emphasis was given to studies using other mushrooms, especially those presenting efforts of attributing hepatoprotective activities to specific chemical components usually present in the mushroom extracts. PMID:23884116
NASA Technical Reports Server (NTRS)
Protection of an aircraft and each of its various systems against the direct effects of lightning were analyzed. Components located in different sections of the aircraft were individually examined since they are likely to experience different degrees of susceptibility to lightning, and may be vulnerable to different components of the lightning flash. The basic steps to be followed in establishing lightning protection were presented by discussing the varieties of arc entry and current flow-through damage. The lightning-strike zones and lightning current environments are established, since environmental conditions in the zones are those under which specific protective measures must perform. Airworthiness regulations which apply to lightning protection are cited.
Interfacial effects in multilayers
Barbee, T.W., Jr.
Interfacial structure and the atomic interactions between atoms at interfaces in multilayers or nano-laminates have significant impact on the physical properties of these materials. A technique for the experimental evaluation of interfacial structure and interfacial structure effects is presented and compared to experiment. In this paper the impact of interfacial structure on the performance of x-ray, soft x-ray and extreme ultra-violet multilayer optic structures is emphasized. The paper is concluded with summary of these results and an assessment of their implications relative to multilayer development and the study of buried interfaces in solids in general.
Proximity effect correction optimization considering fogging and loading effects compensation
Seung-Hune Yang; Yo-Han Choi; Jong R. Park; Yong-Hoon Kim; Seong-Woon Choi; Jung-Min Sohn
Recently, the interest in enhancement of critical dimension (CD) accuracy has been significantly increased to satisfy requirements of sub 100nm devices. Proximity effect correction becomes an indispensable choice to improve CD accuracy within local area, and fogging and loading effects compensation has been tried to enhance global CD uniformity. However, proximity effect correction (PEC) parameters obtained without considering additional exposure
Managing Chemotherapy Side Effects: Pain
... anD human services national institutes of health Managing Chemotherapy Side Effects Pain ōI was worried about getting ... need help to pay for pain medicine. Managing Chemotherapy Side Effects: Pain Keep track of the pain. ...
NASA Technical Reports Server (NTRS)
Chestnutt, D. (editor)
Simulation of inflight fan noise and flight effects was discussed. The status of the overall program on the flight effects of fan noise was reviewed, and flight to static noise comparisons with the JT15D engine were displayed.
Atomistic and orthoatomistic effect algebras
Tkadlec, Josef [Department of Mathematics, Faculty of Electrical Engineering, Czech Technical University, 166 27 Praha (Czech Republic)
We characterize atomistic effect algebras, prove that a weakly orthocomplete Archimedean atomic effect algebra is orthoatomistic and present an example of an orthoatomistic orthomodular poset that is not weakly orthocomplete.
The U.S. Environmental Protection Agency (EPA) initiated a program to evaluate an Improved Laboratory Dispersant Effectiveness Test (ILDET) which was developed to replace EPA's Revised Standard Dispersant Effectiveness Test (RSDET). The report summarizes the development of the IL...
HIV Medicines and Side Effects
... depend on a personÆs individual needs. Can HIV medicines cause side effects? HIV medicines help people with ... are common short-term side effects from HIV medicines? When starting an HIV medicine for the first ...
Ecotoxicological effects extrapolation models
Suter, G.W. II
One of the central problems of ecological risk assessment is modeling the relationship between test endpoints (numerical summaries of the results of toxicity tests) and assessment endpoints (formal expressions of the properties of the environment that are to be protected). For example, one may wish to estimate the reduction in species richness of fishes in a stream reach exposed to an effluent and have only a fathead minnow 96 hr LC50 as an effects metric. The problem is to extrapolate from what is known (the fathead minnow LC50) to what matters to the decision maker, the loss of fish species. Models used for this purpose may be termed Effects Extrapolation Models (EEMs) or Activity-Activity Relationships (AARs), by analogy to Structure-Activity Relationships (SARs). These models have been previously reviewed in Ch. 7 and 9 of and by an OECD workshop. This paper updates those reviews and attempts to further clarify the issues involved in the development and use of EEMs. Although there is some overlap, this paper does not repeat those reviews and the reader is referred to the previous reviews for a more complete historical perspective, and for treatment of additional extrapolation issues.
Ganichev, S D; Ivchenko, E L; Bel'kov, V V; Tarasenko, S A; Sollinger, M; Weiss, D; Wegscheider, W; Prettl, W
There is much recent interest in exploiting the spin of conduction electrons in semiconductor heterostructures together with their charge to realize new device concepts. Electrical currents are usually generated by electric or magnetic fields, or by gradients of, for example, carrier concentration or temperature. The electron spin in a spin-polarized electron gas can, in principle, also drive an electrical current, even at room temperature, if some general symmetry requirements are met. Here we demonstrate such a 'spin-galvanic' effect in semiconductor heterostructures, induced by a non-equilibrium, but uniform population of electron spins. The microscopic origin for this effect is that the two electronic sub-bands for spin-up and spin-down electrons are shifted in momentum space and, although the electron distribution in each sub-band is symmetric, there is an inherent asymmetry in the spin-flip scattering events between the two sub-bands. The resulting current flow has been detected by applying a magnetic field to rotate an optically oriented non-equilibrium spin polarization in the direction of the sample plane. In contrast to previous experiments, where spin-polarized currents were driven by electric fields in semiconductor, we have here the complementary situation where electron spins drive a current without the need of an external electric field. PMID:12000954
NASA Technical Reports Server (NTRS)
Schoenster, James A.; Jones, Michael G.
An experiment was conducted to determine the effect of acoustics on the laminar flow on the side of a nacelle. A flight test was designed to meet this goal and a brief review of the purpose is given. A nacelle with a significant length of laminar flow was mounted on the wing of NASA OV-1. Two noise sources are also mounted on the wing: one in the center body of the nacelle; the second in a wing mounted pod outboard of the nacelle. These two noise sources allow for a limited study of the effect of source direction in addition to control of the acoustic level and frequency. To determine the range of Tollmien-Schlichting frequencies, a stability analysis using the pressure coefficient distribution along the side of the nacelle was performed. Then by applying these frequencies and varying the acoustic level, a study of the receptivity of the boundary layer to the acoustic signal, as determined by the shortening of the length of laminar flow, was conducted. Results are briefly discussed.
Mikhail Lemeshko; Bretislav Friedrich
We present the physics of the quantum Zeno effect, whose gist is often expressed by invoking the adage "a watched pot never boils". We review aspects of the theoretical and experimental work done on the effect since its inception in 1977, and mention some applications. We dedicate the article - with our very best wishes - to Rudolf Zahradnik at the occasion of his great jubilee. Perhaps Rudolf's lasting youthfulness and freshness are due to that he himself had been frequently observed throughout his life: until the political turn-around in 1989 by those who wished, by their surveillance, to prevent Rudolf from spoiling the youth by his personal culture and his passion for science and things beautiful and useful in general. This attempt had failed. Out of gratitude, the youth has infected Rudolf with its youthfulness. Chronically. Since 1989, Rudolf has been closely watched by the public at large. For the same traits of his as before, but with the opposite goal and for the benefit of all generations. We relish keeping him in sight ...
Fox, Patrick J.; Liu, Jia; Tucker-Smith, David; Weiner, Neal
We describe a method to couple Z' gauge bosons to the standard model (SM), without charging the SM fields under the U(1)', but instead through effective higher-dimension operators. This method allows complete control over the tree-level couplings of the Z' and does not require altering the structure of any of the SM couplings, nor does it contain anomalies or require introduction of fields in nonstandard SM representations. Moreover, such interactions arise from simple renormalizable extensions of the SMŚthe addition of vectorlike matter that mixes with SM fermions when the U(1)' is broken. We apply effective Z' models as explanations ofmoreĀ╗various recent anomalies: the D0 same-sign dimuon asymmetry, the CDF W+di-jet excess and the CDF top forward-backward asymmetry. In the case of the W+di-jet excess we also discuss several complementary analyses that may shed light on the nature of the discrepancy. We consider the possibility of non-Abelian groups, and discuss implications for the phenomenology of dark matter as well.½Āless
JPL Test Effectiveness Analysis
NASA Technical Reports Server (NTRS)
Shreck, Stephanie; Sharratt, Stephen; Smith, Joseph F.; Strong, Edward
1) The pilot study provided meaningful conclusions that are generally consistent with the earlier Test Effectiveness work done between 1992 and 1994: a) Analysis of pre-launch problem/failure reports is consistent with earlier work. b) Analysis of post-launch early mission anomaly reports indicates that there are more software issues in newer missions, and the no-test category for identification of post-launch failures is more significant than in the earlier analysis. 2) Future work includes understanding how differences in Missions effect these analyses: a) There are large variations in the number of problem reports and issues that are documented by the different Projects/Missions. b) Some missions do not have any reported environmental test anomalies, even though environmental tests were performed. 3) Each project/mission has different standards and conventions for filling out the PFR forms, the industry may wish to address this issue: a) Existing problem reporting forms are to document and track problems, failures, and issues (etc.) for the projects, to ensure high quality. b) Existing problem reporting forms are not intended for data mining.
Effectively Stable Dark Matter
Cheung, Clifford
We study dark matter (DM) which is cosmologically long-lived because of standard model (SM) symmetries. In these models an approximate stabilizing symmetry emerges accidentally, in analogy with baryon and lepton number in the renormalizable SM. Adopting an effective theory approach, we classify DM models according to representations of $SU(3)_C\\times SU(2)_L\\times U(1)_Y \\times U(1)_B\\times U(1)_L$, allowing for all operators permitted by symmetry, with weak scale DM and a cutoff at or below the Planck scale. We identify representations containing a neutral long-lived state, thus excluding dimension four and five operators that mediate dangerously prompt DM decay into SM particles. The DM relic abundance is obtained via thermal freeze-out or, since effectively stable DM often carries baryon or lepton number, asymmetry sharing through the very operators that induce eventual DM decay. We also incorporate baryon and lepton number violation with a spurion that parameterizes hard breaking by arbitrary units. Howev...
NASA Astrophysics Data System (ADS)
Zhang, Shoucheng
Search for topologically non-trivial states of matter has become a prime goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. We show that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the electronic state changes at a critical thickness. This is a topological quantum phase transition between a conventional insulating phase and a phase exhibiting the QSH effect with a single pair of helical edge states. This theoretical proposal has been tested in a recent experiment carried out at University of Wuerzburg, and the distinct signatures of the QSH state have been experimentally observed. Note from Publisher: This article contains the abstract only.
Faroon, O; Roney, N; Taylor, J; Ashizawa, A; Lumpkin, M H; Plewak, D J
Acrolein is a chemical used as an intermediate reactive aldehyde in chemical industry. It is used for synthesis of many organic substances, methionine production, and methyl chloride refrigerant. The general population is exposed to acrolein via smoking, second-hand smoke, exposure to wood and plastic smoke. Firefighters and population living or working in areas with heavy automotive traffic may expose to higher level of acrolein via inhalation of smoke or automotive exhaust. Degradation of acrolein in all environmental media occurs rapidly, therefore, environmental accumulation is not expected. Acrolein degrade in 6A days when applied to surface water, and it has not been found as a contaminant in municipal drinking water. Acrolein vapor may cause eye, nasal and respiratory tract irritations in low level exposure. A decrease in breathing rate was reported by volunteers acutely exposed to 0.3A ppm of acrolein. At similar level, mild nasal epithelial dysplasia, necrosis, and focal basal cell metaplasia have been observed in rats. The acrolein effects on gastrointestinal mucosa in the animals include epithelial hyperplasia, ulceration, and hemorrhage. The severity of the effects is dose dependent. Acrolein induces the respiratory, ocular, and gastrointestinal irritations by inducing the release of peptides in nerve terminals innervating these systems. Levels of acrolein between 22 and 249 ppm for 10 min induced a dose-related decrease in substance P (a short-chain polypeptide that functions as a neurotransmitter or neuromodulator). PMID:19028774
Transformation of QTL genotypic effects to allelic effects
Nagamine, Yoshitaka
The genotypic and allelic effect models are equivalent in terms of QTL detection in a simple additive model, but the QTL allelic model has the advantage of providing direct information for marker-assisted selection. However, the allelic matrix is four times as large as the genotypic IBD matrix, causing computational problems, especially in genome scans examining multiple positions. Transformation from genotypic to allelic effects, after estimating the genotypic effects with a smaller IBD matrix, can solve this problem. Although the validity of transformation from genotypic to allelic effects has been disputed, this work proves that transformation can successfully yield unique allelic effects when genotypic and allelic IBD matrixes exist. PMID:16093016
Effects of harmonics on equipment
V. E. Wagner; J. C. Balda; T. M. Barnes; A. E. Emannuel; R. J. Ferraro; D. C. Griffith; D. P. Hartmann; W. F. Horton; W. T. Jewell; A. McEachern; D. J. Phileggi; W. E. Reid
The purpose of this paper is to summarize the state-of-knowledge of the effects of power system harmonics on equipment. The general mechanisms presented are thermal overloading, disruption, and dielectric stressing. Quantitative effects are presented or referenced whenever possible. However, many of the effects can only be qualitatively described. The equipment considered are adjustable speed drives, capacitors, circuit breakers, fuses, conductors,
Antimicrobial effect of zinc pyrithione
Synopsis The antimicrobial effect of zinc pyrithione has been studied with healthy scalps in relation to its ANTIDANDRUFF effect. Use of zinc pyrithione-containing shampoo sharply reduced the CORNEOCYTE COUNTS, while the similarly active antimicrobial agent, Irgasan DP-300 ® had no effect on the corneocyte counts. Quantitative estimation of scalp microorganisms revealed that corresponding to the decrease in dandruff, Pityrospbrum ovale
Solar Neutrino Matter Effects Redux
A. B. Balantekin; A. Malkus
Following recent low-threshold analysis of the Sudbury Neutrino Observatory and asymmetry measurements of the BOREXINO Collaboration of the solar neutrino flux, we revisit the analysis of the matter effects in the Sun. We show that solar neutrino data constrains the mixing angle $\\theta_{13}$ poorly and that subdominant Standard Model effects can mimic the effects of the physics beyond the Standard Model.
Effects Of Radiation On Elastomers
NASA Technical Reports Server (NTRS)
Bouquet, Frank L.
Report provides data on effects of radiation on elastomers. Quantifies effects by giving minimum radiation levels to induce changes of 1 percent and 25 percent in given properties. Electrical, mechanical, and chemical properties included in data. Combined effects of heat and radiation briefly considered. Data summarized in graphic form useful to designers.
Emotional intelligence and effective leadership
Benjamin Palmer; Melissa Walls; Zena Burgess; Con Stough
Emotional intelligence has become increasingly popular as a measure for identifying potentially effective leaders, and as a tool for developing effective leadership skills. Despite this popularity, however, there is little empirical research that substantiates the efficacy of emotional intelligence in these areas. The aim of the present paper was to explore the relationship between emotional intelligence and effective leadership. Emotional
"No Effects" Studies Raising Eyebrows
ERIC Educational Resources Information Center
Viadero, Debra
Like a steady drip from a leaky faucet, the experimental studies being released this school year by the federal Institute of Education Sciences are mostly producing the same results: "No effects," "No effects," "No effects." The disappointing yield is prompting researchers, product developers, and other experts to question the design of theģ
Assessing and Improving Institutional Effectiveness.
ERIC Educational Resources Information Center
Cameron, Kim S.
Information to promote assessment of organizational effectiveness in colleges and universities is presented, along with an exercise to rank the effectiveness of 10 institutions. The exercise uses three types of criteria to indicate effectiveness: subjective ratings, data about students and activities, and institutional capacity and financialģ
Cost Effectiveness NW Energy Coalition
1 Action 8 Cost Effectiveness Manual Kim Drury NW Energy Coalition Context Ę Inconsistent understanding of cost effectiveness contributed to under performing conservation E.g: individual measures vs at end of 2009 #12;2 The thinking was . . . That a Cost Effectiveness Guide could: Ę Increase regionally
The Future of Institutional Effectiveness
ERIC Educational Resources Information Center
Alfred, Richard L.
Forces inside and outside community colleges are changing the context for performance and mandating new conceptions of effectiveness. This article addresses the future of institutional effectiveness in community colleges. Its emphasis is on what is measured and why, beginning with a retrospective look at early efforts in effectiveness, moving toģ
Probiotics: mechanisms and established effects
Arthur C. Ouwehand; Pirkka V. Kirjavainen; Colette Shortt; Seppo Salminen
The definition for probiotics has gradually changed with increasing understanding of the mechanisms by which they influence human health. Health effects related to changes in the intestinal microflora also accompany or are related to adhesion and immune system effects, competitive exclusion or metabolic and nutritional effects, with an increasing array of other potential modes of action. Most clinically documented and
Dworza?ski, Wojciech; Opielak, Grzegorz; Burdan, Franciszek
Caffeine is one of the most commonly ingested alkaloids worldwide. It is present in coffee, tea, soft and energy drinks, chocolate, etc. Currently published data has been stressed that the metyloxantine consumption increases the risk of coronary heart disease, arterial hypertension, arterial stiffness, and an elevation of cholesterol and homocysteine plasma concentration. The acute high consumption may also modulate insulin sensitivity and glucose blood level. However, the long-term consumption reduces the incidence of the type 2 diabetes mellitus. When administered in high doses the substance may cause various side effects, related to abnormal stimulation of the central nervous system, decrease tonus of the lower esophageal sphincter, as well as increase risk of miscarriage and intrauterine growth retardation. The final manifestation of side reactions is dependent on the genotype, especially polymorphisms of genes associated with caffeine metabolism, i.e., cytochrome P450-CYP1A2 and catechol-O-methyltransferase (COMT). PMID:19999796
Patel, D R; Homnick, D N
The problems of tobacco addiction have evolved over centuries. The possible relationship between smoking and oral cancer was recognized as early as the 19th century. The use of tobacco results in an estimated 4 million deaths each year worldwide. Approximately 3,000 adolescents start smoking every day; 4.5 million children and adolescents smoke cigarettes; 1 million use smokeless tobacco. This article reviews the effects of environmental tobacco smoke and primary smoking on lung health and maturation and the pathophysiology of smoking-related pulmonary disease. Smoking prevention and timely smoking cessation will significantly reduce the risk of not only lung diseases (chronic obstructive pulmonary disease, cancer, chronic bronchitis, asthma, etc.) but also suboptimal lung growth during preadolescent and adolescent years. PMID:11060554
Crawford, F.S.
The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments.
'Special effects' burn injuries.
Peters, W
Three patients are presented with significant flame burns, resulting from accidents occurring during 'special effects' situations in the entertainment industry. These occurred as a result of the spontaneous combustion of various materials, during events in live theatre (gun powder), a television commercial (artificial 'rocket fuel'), and a video presentation (magnesium oxide). All three patients sustained flash burns to the face and hands. One patient sustained a significant bilateral corneal injury, a gamekeeper's thumb, and a permanent continuous right-sided high frequency tinnitus, in addition to his burn injury. Photographic documentation of all three patients is presented. The total loss of time from work for all patients was 6 months. All these injuries were potentially preventable. PMID:2031675
Crawford, Frank S.
The "hot chocolate effect" was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the ten percent accuracy of the experiments.
NASA Astrophysics Data System (ADS)
Crawford, Frank S.
The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments.
Action languages: Dimensions, effects
NASA Technical Reports Server (NTRS)
Hayes, Daniel G.; Streeter, Gordon
Dimensions of action languages are discussed for communication between humans and machines, and the message handling capabilities of object oriented programming systems are examined. Design of action languages is seen to be very contextual. Economical and effective design will depend on features of situations, the tasks intended to be accomplished, and the nature of the devices themselves. Current object oriented systems turn out to have fairly simple and straightforward message handling facilities, which in themselves do little to buffer action or even in some cases to handle competing messages. Even so, it is possible to program a certain amount of discretion about how they react to messages. Such thoughtfulness and perhaps relative autonomy of program modules seems prerequisite to future systems to handle complex interactions in changing situations.
Effectiveness of price regulation
Meyer, R.A.; Leland, H.E.
That it is easier to measure the costs of price regulation than the benefits is evident in the conflicting results of studies made to determine welfare gains. An econometric study based on a simple theory of demand by customer class concludes that: (1) the effectiveness of regulation across states is irregular, which suggests that state regulatory agencies confront firms with highly variable political climates and may serve customers with an uneven quality of benefits; (2) the pattern of cross-subsidization of prices that penalized residential customers in 1969 was gone or shifted to favor residential customers by 1974; (3) a more-detailed re-evaluation of the presumed benefits and costs of nonuniform pricing may be warranted; and (4) welfare improvements appear to be possible. The dominant question that emerges is how to explain what underlying forces contribute to the substantial state-to-state and between-customer variations in regulatory impact. 13 references, 6 tables.