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Continuous flow microwave sterilization is an emerging technology that has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temperature range of 20 to 130 degrees C and compared with those measured by the conventional approach (under static conditions). The food products chosen for this study were skim milk, green pea puree, carrot puree, and salsa con queso. Second-order polynomial correlations for the dependence of dielectric properties at 915 MHz of the food products on temperature were developed. Dielectric properties measured under static and continuous flow conditions were similar for homogeneous food products such as skim milk and vegetable puree, but they were significantly different for salsa con queso, which is a multiphase food product. The results from this study suggest that, for a multiphase product, dielectric properties measured under continuous flow conditions should be used for designing a continuous flow microwave heating system. PMID:17995769
Kumar, P; Coronel, P; Simunovic, J; Truong, V D; Sandeep, K P
Static dielectric constant, viscosity, and structure of pure isomeric pentanols
Static dielectric constants, viscosities, densitites and refractive indices of 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-methyl-2-butanol were measured at 15, 25, 35 and 45░C. These results together with the previous data on n-pentanol have been analyzed in terms of the Kirkwood correlation factor gk and of the energy of activiation for viscous flow. With the exception of 2-methyl-2-butanol, gk was found
Alessandro D'Aprano; Dorina I. Donato; Valeria Agrigento
Dielectric properties of gel collected from shark electrosensors
To investigate the physical mechanism of the electric sense, we present an initial characterization of the dielectric properties of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranches (sharks, skates, and rays). To ascertain the properties of the gel, low-frequency impedance spectroscopy is used. The impedance data collected from a dialyzed sample show large values of static permittivity
Mary E. Hughes; Brandon R. Brown; John C. Hutchison; Royce W. Murray
Estimate of the intermolecular polarization contribution to the static dielectric constant of water
In this paper, molecular-structure data derived from recent quantum-chemical studies are used in conjunction with the Mandel-Mazur theory of the static dielectric constant to estimate the importance of intermolecular polarization contributions to the static dielectric constant of water. A scalar expression for the static dielectric constant is identified and then investigated via a multibody decomposition in which the effects of
James W. Kress; John J. Kozak
Dielectric properties of PMT-PT crystals
NASA Astrophysics Data System (ADS)
Results of broadband dielectric investigations of 0.94PbMg1/3Ta2/3O3-0.06PbTiO3 (0.94PMT-0.06PT or PMT-PT) crystals in wide temperature range from 100 K to 950 K are presented. Below 300 K the dielectric properties of crystals are governed by polar nanoregions dynamics. However, at higher temperatures (above 600 K) the electrical conductivity effects also become important. The electrical conductivity occurs presumably due the hopping of oxygen vacancies and demonstrates change in the activation energy close to 750 K. The change in the activation energy can be explained by increase of concentration of single ionized vacancies. No anomaly in the temperature dependence of the static dielectric permittivity was observed in wide temperature range from 213 K to 950 K and the dependence was successfully described by spherical random bonds random fields theory. Moreover, two different contributions were successfully separated in the distributions of relaxation times in PMT-PT crystals. These contributions were attributed to different polar nanoregions dynamics. Moreover, the different freezing temperatures values were obtained for most probable and longest relaxation times, which was explained with an idea of continuous distribution of relaxation times broadening on cooling in relaxors. The critical remarks about the Vogel-Fulcher law application for relaxors are addressed in the paper.
Palaimiene, E.; Macutkevic, J.; Banys, J.; Kania, A.
Dielectric properties of gel collected from shark electrosensors
NASA Astrophysics Data System (ADS)
To investigate the physical mechanism of the electric sense, we present an initial characterization of the dielectric properties of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranches (sharks, skates, and rays). To ascertain the properties of the gel, low-frequency impedance spectroscopy is used. The impedance data collected from a dialyzed sample show large values of static permittivity and a loss peak corresponding to a long relaxation time (about 1 ms). Impedance measurements of the native (nondialyzed) gel reliable to 0.1 Hz will be presented and compared to the dialyzed gel. Ramifications of the gel's dielectric properties for the electric sense will be explored.
Hughes, Mary E.; Brown, Brandon R.; Hutchison, John C.; Murray, Royce W.
The Statics Dielectric Function and Interaction Potential In Strong Coupling With AdS/CFT
In this paper, we studied the static dielectric function and interaction potential in strong coupling limit with AdS/CFT correspondence. The dielectric function is depressed compared with that in weak coupling. The interaction potential then presents a weaker screening characteristics in strong coupling, which indicates a smaller Debye mass compared with weak coupling.
Lian Liu; Xuan-min Cao; Hui Liu
Static Dielectric Function and Interaction Potential in Strong Coupling with AdS/CFT
NASA Astrophysics Data System (ADS)
In this paper, we study the static dielectric function and interaction potential in strong coupling limit with AdS/CFT correspondence. The dielectric function is depressed compared with that in weak coupling. The interaction potential then presents a weaker screening characteristics in strong coupling, which indicates a smaller Debye mass compared with weak coupling.
Liu, Lian; Cao, Xuan-Min; Liu, Hui
Microwave dielectric properties of boreal forest trees
NASA Technical Reports Server (NTRS)
The knowledge of vegetation dielectric behavior is important in studying the scattering properties of the vegetation canopy and radar backscatter modelling. Until now, a limited number of studies have been published on the dielectric properties in the boreal forest context. This paper presents the results of the dielectric constant as a function of depth in the trunks of two common boreal forest species: black spruce and trembling aspen, obtained from field measurements. The microwave penetration depth for the two species is estimated at C, L, and P bands and used to derive the equivalent dielectric constant for the trunk as a whole. The backscatter modelling is carried out in the case of black spruce and the results are compared with the JPL AIRSAR data. The sensitivity of the backscatter coefficient to the dielectric constant is also examined.
Xu, G.; Ahern, F.; Brown, J.
Pyroelectric and dielectric properties of ceramics
NASA Astrophysics Data System (ADS)
Ferroelectric oxide ceramics have been investigated as possible alternatives to highly sensitive triglycine sulfate (TGS) crystals for their use in room temperature infrared detectors. In this paper dielectric and pyroelectric properties of some ceramics based on modified lead titanate and others are presented. The figures-of-merit of these ceramics calculated using the measured dielectric and pyroelectric data are presented. The relative advantages and disadvantages of the principal ceramic systems are also compared with existing materials reported in the literature.
Batra, A. K.; Moxon, Ryan; Guggilla, Padmaja; Aggarwal, M. D.; Edwards, M. E.
An ab-initio Computational Method to Determine Dielectric Properties of Biological Materials
Frequency dependent dielectric properties are important for understanding the structure and dynamics of biological materials. These properties can be used to study underlying biological processes such as changes in the concentration of biological materials, and the formation of chemical species. Computer simulations can be used to determine dielectric properties and atomic details inaccessible via experimental methods. In this paper, a unified theory utilizing molecular dynamics and density functional theory is presented that is able to determine the frequency dependent dielectric properties of biological materials in an aqueous solution from their molecular structure alone. The proposed method, which uses reaction field approximations, does not require a prior knowledge of the static dielectric constant of the material. The dielectric properties obtained from our method agree well with experimental values presented in the literature. PMID:23652459
Abeyrathne, Chathurika D.; Halgamuge, Malka N.; Farrell, Peter M.; Skafidas, Efstratios
Dielectric properties of Ekibastuz coal
An investigation was carried out into the relationships between the dielectric loss angle of an Ekibastuz brown coal, its moisture and ash and the electric field frequency. It has been demonstrated that it is, in principle, possible to measure the ash and moisture contents of this coal by a high-frequency multi-parameter method.
Protopopov, O.A.
Dielectric nanocomposites with insulating properties
Polymer nanocomposites possess promising high performances as engineering materials, if they are prepared and fabricated properly. Some work has been recently done on such polymer nanocomposites as dielectrics and electrical insulation. This was reviewed in 2004 based on the literatures published up to 2003. New significant findings have been added since then. Furthermore, a multi-core model with the far-distance effect,
Toshikatsu Tanaka
Static and dynamic properties of Fibonacci multilayers
NASA Astrophysics Data System (ADS)
We theoretically investigate static and dynamic properties of quasiperiodic magnetic multilayers. We considered identical ferromagnetic layers separated by non-magnetic spacers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr, the minimum energy was determined and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. Regarding dynamic behavior, ferromagnetic resonance (FMR) curves were calculated using an approximation known from the literature. Our numerical results illustrate the effects of quasiperiodicity on the static and dynamic properties of these structures.
Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A.
How does static stretching decrease the dielectric constant of VHB 4910 elastomer?
NASA Astrophysics Data System (ADS)
Subject to a voltage, dielectric elastomers deform by the effect of Maxwell stress which is depended directly on the dielectric constant of the material. The combination of large strain, soft elastic response and good dielectric properties has established VHB 4910 elastomer as the most used material for dielectric elastomer actuators. However, the effect of stretch on the dielectric constant for this elastomer is much debated topic while controversy results are demonstrated in the literature. The dielectric constant of this material is studied and demonstrated that it decreases slightly or hugely among the stretch but any pertinent response and any physic explications are validated by the scientific community. In this paper, we presented a detail study about dielectric behavior of VHB 4910 elastomer versus a broadband of stretch and temperature. We found that the dielectric constant of this material depends strongly on the stretch following a polynomial law. Among all the explanations of stretch dependence of the dielectric constant of VHB 4910 in the literature: the crystallization, the change of glass transition temperature, the decrease of dipole orientation, the electrostriction effect under stress; and based on our experimental result, we conclude that the decrease of dipole orientation seems the main reason to the drop of dielectric constant of VHB 4910 elastomer versus the stretch. We proposed also an accurate model describing the dielectric constant of this material for a large range of stretch and temperature.
Vu-Cong, T.; Nguyen-Thi, N.; Jean-Mistral, C.; Sylvestre, A.
Microwave dielectric properties of plant materials
NASA Technical Reports Server (NTRS)
Three waveguide transmission systems covering the 1-2, 3.5-6.5, and 7.5-8.5 GHZ bands were used to measure the dielectric properties of vegetation material as a function of moisture content and microwave frequency. The materials measured included, primarily, the leaves and stalks of corn and wheat. Dielectric measurements also were made of the liquid included in the vegetation material after it was extracted from the vegetation by mechanical means. The extracted liquids were found to have an equivalent NaCl salinity of about 10 per mil, which can have a significant effect on the dielectric loss at frequencies below 5 GHz. The results of attempts to model the dielectric constant of the vegetatioon-water mixture in terms of the dielectric constants and volume fractions of its constituent parts (i.e., bulk vegetation, air, bound water, and free water) are discussed. Additionally, measurements of the temporal variations in the total attenuation at 10.2 GHz are presented for a corn canopy and a soybean canopy.
Ulaby, F. T.; Jedlicka, R. P.
Fundamentals of dielectric properties measurements and agricultural applications.
Dielectrics and dielectric properties are defined generally and dielectric measurement methods and equipment are described for various frequency ranges from audio frequencies through microwave frequencies. These include impedance and admittance bridges, resonant frequency, transmission-line, and free-space methods in the frequency domain and time-domain and broadband techniques. Many references are cited describing methods in detail and giving sources of dielectric properties data. Finally a few applications for such data are presented and sources of tabulated and dielectric properties data bases are identified. PMID:21721322
Nelson, Stuart O
frequency dielectric constant of borosilicate glasses has been measured down to 5 mK. A new law in Log T/03C and temperatures. We have measured the very low frequency dielectric constant of a borosilicate glassL-153 NEW DIELECTRIC PROPERTIES OF GLASSES AT VERY LOW TEMPERATURES G. FROSSATI, R. MAYNARD, R
Paris-Sud XI, Universit├® de
Complex Dielectric Properties of Sulfate-Reducing Bacteria Suspensions
Sulfate-reducing bacteria (SRB) can potentially enhance the remediation of heavy metals in the subsurface. Previous geophysical research has demonstrated the sensitivity of electrical measurements to SRB mediated mineral transformation in porous media. However, the inherent dielectric properties of SRB and their direct contribution to the electrical properties of porous media are poorly understood. We studied the complex dielectric properties of
Chi Zhang; Lee Slater; Camelia Prodan
The dielectric properties of polymer-water systems
THE DIELECTRIC PROPERTIES OF POLYMER- WATER SYSTEMS A Thesis by JOE BILL LEWIS Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE December 1976 Major... Subject: Chemistry THE DIELECTRIC PROPERTIES OF POLYMER- WATER SYSTEMS A Thesis by JOE SILL LEWIS Approved as to style and content by: C z Cnairman, o Comni ttee Head of Department 1 I Member Member December 1976 ABSTRACT The Dielectric...
Lewis, Joe Bill
Millimeter wave and terahertz dielectric properties of biological materials
Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to
Usman Ansar Khan
Dielectric properties of cottage cheese and surface treatment using microwaves
This research determines the dielectric properties of cottage cheese and explores the application of microwave treatment to reduce surface spoilage microorganisms, extending the shelf-life of cottage cheese in sealed plastic containers. Dielectric properties of cottage cheese of 0, 2 and 4% fat content were measured at temperatures between 5 and 65 ░C. The penetration depths of microwaves of 2450 and
A. G. Herve; J. Tang; L. Luedecke; H. Feng
Microwave dielectric properties of dry rocks
NASA Technical Reports Server (NTRS)
A combination of techniques was used to measure the dielectric properties of 80 rock samples in the microwave region. The real part (RP) of the relative dielectric constant was measured in 0.1-GHz steps from 0.5 to 18 GHz, and the imaginary part (IP) was measured at five frequencies between 1.6 and 16 GHz. The bulk density rho(b) was also measured for all the samples, and the bulk chemical composition (BCC) was determined for 56 of the samples. RP is found to be frequency-independent at 0.5-18 GHz for all samples, and rho(b) accounts for about 50 percent of the observed variance. For silicate rocks, as much as 78 percent of the variance is explained by the combination of rho(b) and the fractional contents of oxides when the silicates are subgrouped by genesis. In contrast, IP decreases with increasing frequency for most rock samples, and no statistically significant relationships are found between IP and rho(b). For subgrouped silicate rocks, 60 percent of the variance in IP can be explained by BCC.
Ulaby, Fawwaz T.; Dobson, Myron C.; East, Jack R.; Bengal, Thomas H.; Garvin, James B.; Evans, Diane L.
Electrophysical properties of dielectric films in MDM-structures
NASA Astrophysics Data System (ADS)
Using the methods of reactive cathode sputtering in a low-voltage, penning-discharge installation, dielectric films from silica, silicon nitride, aluminum nitride, etc. are obtained. Parameters of the films in MDM structures, their optical properties and porosity are investigated as a function of the deposition rate, substrate temperature and reaction gas pressure. It is found out that the films from silicon nitride exhibit the highest dielectric strength and those from silicon dioxide show the least dielectric loss.
Danilina, T. I.; Troyan, P. E.
Dielectric properties of lead-magnesium niobate ceramics
Dielectric properties are reported for lead magnesium niobate (PbMg ŌüŌ Nb ŌŌ OŌ) ceramics which were prepared as single phase (i.e., without pyrochlore) with an improved technique. Dielectric constants of 18,000 for pure PMN and 31,000 for PMN with 10% PbTiOŌ were achieved; these values are 50% larger than those reported in the literature. The dielectric constant of PMN ceramics
S. L. Swartz; T. R. SHROUT; W. A. SCHULZE; L. E. CROSS
First-principles study of dielectric properties of cerium oxide
We have theoretically investigated the dielectric properties of fluorite CeO2 as well as hexagonal and cubic Ce2O3 by using first-principles pseudopotentials techniques within the local density approximation. Calculated electronic and lattice dielectric constants of CeO2 are in good agreement with previous theoretical and experimental results. For Ce2O3, the hexagonal phase has a lattice dielectric constant comparable to that of CeO2,
Takenori Yamamoto; Hiroyoshi Momida; Tomoyuki Hamada; Tsuyoshi Uda; Takahisa Ohno
High-? gate dielectrics: Current status and materials properties considerations
Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 ?m complementary metal¢oxide¢semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film
G. D. Wilk; R. M. Wallace; J. M. Anthony
We analyzed the dielectric properties of molecular liquids using the external field method with reaction field approximations. The applicability of this method to determine the dielectric properties of molecules with zero (1,4-dioxane) and non-zero (water and bio-molecular aqueous solutions) permanent dipole moment was studied. The relative static dielectric constant obtained using the external field method for polar and non-polar molecular liquids, including molecules with zero permanent dipole moment, agreed well with the experimental values presented in the literature. Our results indicate that the Debye relaxation time constants estimated from the non-equilibrium simulations using the external field method were accurate for molecules whose permanent dipole moments were less than 12 D. PMID:24899067
Abeyrathne, Chathurika D; Halgamuge, Malka N; Farrell, Peter M; Skafidas, Efstratios
The static actuation of dielectric elastomer actuators: how does pre-stretch improve actuation?
It has previously been shown that providing dielectric elastomer actuators with a level of pre-stretch can improve properties such as breakdown strength, actuation strain and efficiency. The actuation in such actuators depends on an interplay between the highly nonlinear hyperelastic stress-strain behaviour with the electrostatic Maxwell's stress; however, the direct effects of pre-stretch on the electromechanical coupling have still not
Guggi Kofod
Dielectric properties of barium titanate supramolecular nanocomposites.
Nanostructured dielectric composites can be obtained by dispersing high permittivity fillers, barium titanate (BTO) nanocubes, within a supramolecular framework. Thin films of BTO supramolecular nanocomposites exhibit a dielectric permittivity (?r) as high as 15 and a relatively low dielectric loss of ?0.1 at 1 kHz. These results demonstrate a new route to control the dispersion of high permittivity fillers toward high permittivity dielectric nanocomposites with low loss. Furthermore, the present study shows that the size distribution of nanofillers plays a key role in their spatial distribution and local ordering and alignment within supramolecular nanostructures. PMID:24584569
Lee, Keun Hyung; Kao, Joseph; Parizi, Saman Salemizadeh; Caruntu, Gabriel; Xu, Ting
Relationship between Dielectric Properties and Microphonics of Mulutilayer Ceramic Capacitors
NASA Astrophysics Data System (ADS)
As a result of investigating the relationship between the dielectric properties of BaTiO3-based dielectrics and the microphonics of multilayer ceramic capacitors (MLCCs), it was confirmed that microphonics, electric-induced strain, and polarization have very high correlation, and piezostriction becomes dominant in electric-induced strain when high DC bias is applied to BaTiO3-based dielectrics in spite of their very low spontaneous polarizations. Dielectrics with a large paraelectric phase area in which rare-earth elements have diffused into BaTiO3 are useful for applications of MLCCs, especially under high DC bias.
Inoue, Noriyuki; Kawasaki, Kenichi; Sano, Harunobu; Morimoto, Tadashi
Millimeter wave and terahertz dielectric properties of biological materials
NASA Astrophysics Data System (ADS)
Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to polarization and birefringence effects, it was determined that one can not utilize the dielectric properties of powder-containing packages to differentiate hoax attacks and serious security threats.
Khan, Usman Ansar
Dielectric properties of human placenta, umbilical cord and amniotic fluid
NASA Astrophysics Data System (ADS)
The dielectric properties of freshly delivered human placenta, umbilical cord and amniotic fluid have been acquired at 37 ░C and in the frequency range of 200 MHz-10 GHz. The experimental data were fitted to a Cole-Cole expression. The results show that dielectric properties of the umbilical cord are significantly higher than placenta due to the presence of high water content Wharton's jelly. The results also demonstrate large differences in the dielectric properties of amniotic and cerebrospinal fluids. The data presented can be used in numerical simulations of the exposure of pregnant women to electromagnetic fields.
Peyman, A.; Gabriel, C.; Benedickter, H. R.; Fr÷hlich, J.
Structural aspects in the dielectric properties of pentyl alcohols
NASA Astrophysics Data System (ADS)
At temperatures between 0 and 60 ░C densities, shear viscosities and dielectric spectra have been measured for isomers 1-pentanol, 2-pentanol, 3-pentanol, isopentylalcohol, and tert-pentanol, as well as for mixtures of these alcohols. The density and shear viscosity data are discussed in terms of deviations from ideal mixing behavior. The dielectric spectra are evaluated to yield the extrapolated static permittivity and the relaxation time of the principal (low-frequency) relaxation term. The former parameter is analyzed in view of dipole orientation correlations, the latter one is discussed in terms of the activation enthalpy controlling the relaxation process. A noticeable result is the effect of isomer structure on both the dipole orientation correlation and the dielectric relaxation. Especially the dielectric parameters of tert-pentanol deviate significantly from the relevant parameters of the other pentanols. Such deviations are considered in the light of models of hydrogen network structure and fluctuations.
Kaatze, Udo; Behrends, Ralph; von Roden, Kerstin
Ultralow Dielectric Property of Electrospun Polylactide-Polyglycolide Nanofibrous Membranes
NASA Astrophysics Data System (ADS)
Polylactide-polyglycolide (PLGA) has been one of the most important biodegradable and biocompatible materials. In this study, nanofibrous membranes of PLGA were fabricated using an electro fiber spinning setup that consisted of a syringe and needle (the internal diameter is 0.42 mm), a ground electrode, an aluminum sheet, and a high voltage supply. The dielectric properties of the electrospun membranes were characterized. The experimental results suggested that the electrospun membranes exhibited ultralow dielectric behavior. The influences of the nanofibers diameter and the density of the membranes on the dielectric properties were also instigated. It was found that the dielectric constants decreased with the fiber diameter and increased with the density of the nanofibrous membranes. By employing the electrospinning process, one will be able to fabricate polymeric membranes with ultralow dielectric performance.
Liu, Shih-Jung; Chiou, Lung-Yi; Liao, Jun-Yi
On thermodynamic and dielectric properties of PbHPO4 and PbHAsO4 crystals
NASA Astrophysics Data System (ADS)
Thermodynamic and dielectric properties of PbHPO4 and PbHAsO4 crystals are studied using the pseudo-spin model for proton subsystem within a two-particle cluster approximation neglecting the proton tunneling on hydrogen bonds. Temperature dependence of spontaneous polarization, heat capacity, static dielectric permittivity and dielectric dispersion in wide frequency range is calculated for both compounds in two structural phases. At a proper set of model parameters, a good quantitative description of the corresponding experimental data is obtained.
Zachek, I. R.; Shchur, Ya.; Levitskii, R. R.; Bilenka, O. B.
Electrical Properties and Dielectric Relaxation of DNA in Solution.
National Technical Information Service (NTIS)
In this report the authors overview and summarize the electrical properties and dielectric relaxation of solvenated DNA. The authors review models for counterion dynamics, dipole moment, polarizability, and relaxation in both double- and single-stranded D...
J. Baker-Jarvis, C. A. Jones, B. Riddle
Static and dynamic properties of a two-dimensional charged Bose fluid
NASA Astrophysics Data System (ADS)
We investigate some static and dynamic properties of a two-dimensional charged Bose fluid interacting via ln (r) potential by using the self-consistent-field approximation of Singwi, Tosi, Land, and Sj÷autlander. The static structure factor, the pair-correlation function, the energy spectrum of elementary excitations, and the static dielectric-response function are calculated over a wide density range (1<=rs<=10). Wherever available, the results for the structure factor are compared with the recent diffusion Monte Carlo calculation by Magro and Ceperley and a good agreement is found. A comparison is also made with the two-dimensional charged Bose fluid with 1/r interaction potential. It is noticed that the Bose fluid interacting with ln (r) potential becomes partially localized at rs~10, which is closer to the Monte Carlo prediction of Wigner crystallization at rs~12.
Moudgil, R. K.; Ahluwalia, P. K.; Tankeshwar, K.; Pathak, K. N.
Conducting dielectric polymer properties at Terahertz wavelength
The dielectric function of polyaniline (Pani) doped by couple drug\\/solvent sulphonic camphoracid\\/dichloroacetic CSA\\/DCAA is studied in the terahertz range. Numerous films of this polymer with different doping level are measured by Terahertz Time-Domain Spectroscopy (THz-TDS). The Fourier transmission spectrum, the permittivity and conductivity are then precisely obtained between 0.1 and 4 THz. The behavior of the dielectric function does not
E. Nguema; J. D. Delagnes; A. Elfatimy; P Mounaix
Dielectric properties of some vegetable oils
SummaryĀĀThe density, the refractive index and the dielectric constants at room temperature (26░) are determined for the solutions\\u000a of castor oil, olive oil, sesame oil and cocoanut oil in benzene. The dielectric constants were determined at 30 meters (10,000\\u000a Kc.) by observing the resonance with the help of a valve-voltmeter. It is found that in very dilute solutions the molecules
G. R. Paranjpe; P. Y. Deshpande
Optical Transmission Properties of Dielectric Aperture Arrays
NASA Astrophysics Data System (ADS)
Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index units (RIU) and a dynamic range as large as 0.17 RIU. Subsequently, optical transmission properties through a self-mixing interferometer array are studied and a novel high-resolution cost-effective optical spectrometer is proposed. The miniature interferometer-based spectrometer is made of polymethyl methacrylate (PMMA) with a CCD as the detector. The detected intensity of each CCD pixels contains the spectral information. Since each frequency component in the incoming beam corresponds to a unique phase difference of the two beam portions of each optical interferometer, the total intensity received by each CCD pixel, which is resulted from the addition of the interference signals from all the frequency components in the beam, should also be unique. Therefore, the spectrum calculation is a problem to solve an ill-posed linear system by using Tikhonov regularization method. Simulation results show that the resolution can reach picometer level. Apart from the choice of path difference between the interfering beams, the spectral resolution also depends on the signal-to-noise ratio and analogue-digital conversion resolution (dynamic range) of the CCD chip. In addition, the theory of uniform waveguide scattering is explored to expand the possibility of using such mini-interferometers for performing free-space spectral analysis of waveguide devices. At the same time, the method of least squares is used to correct the pixel non-uniformity of the CCD so as to improve the performance of the spectrometer. The sensor chip and spectrometer chip introduced here are based on the interference of light transmitted through dielectric aperture arrays. Their compact feature renders these devices ideal for miniaturization and integration as the systems in microfluidics architectures and lab-on-chip designs.
Yang, Tao
Collective and static properties of model two-component plasmas.
Classical MD data on the charge-charge dynamic structure factor of two-component plasmas (TCP) modeled in Phys. Rev. A 23, 2041 (1981) are analyzed using the sum rules and other exact relations. The convergent power moments of the imaginary part of the model system dielectric function are expressed in terms of its partial static structure factors, which are computed by the method of hypernetted chains using the Deutsch effective potential. High-frequency asymptotic behavior of the dielectric function is specified to include the effects of inverse bremsstrahlung. The agreement with the MD data is improved, and important statistical characteristics of the model TCP, such as the probability to find both electron and ion at one point, are determined. PMID:17930158
Arkhipov, Yu V; Askaruly, A; Ballester, D; Davletov, A E; Meirkanova, G M; Tkachenko, I M
Static properties of granular materials In this chapter, we are interested in static pilings in another language than english, as well as conference proceedings or reviews difficult to access. 1 Statics at the grain scale 1.1 Static solutions Equilibrium conditions Let us consider a single grain in a granular
Claudin, Philippe
Effect of sorbed oil on the dielectric properties of sand and clay
NASA Astrophysics Data System (ADS)
The dielectric response of geologic materials is related to the amount of water-wetted solid surface present. This dependence raises the possibility that dielectric measurements may be used to detect changes in the state of the solid-fluid interface such as those caused by the sorption of a chemical species. In this study, complex impedance data are collected for systems of clean and oil-bearing sand and kaolinite vacuum- saturated with a 0.001 M NaCl brine in the frequency range 100 kHz to 10 MHz. The effective dielectric constant k and electrical conductivity ? of the samples are calculated from these measurements assuming quasi-static conditions. We define the components in our system as brine, air, and a "wetted" solid phase. In this way, the contribution of the solid-fluid interface to the bulk dielectric response is included in the last component. We use an inclusion-based effective medium theory to extract the dielectric response of the wetted solid from the experimental data. The presence of sorbed oil is found to have little effect on the dielectric response of the wetted sand matrix, presumably because of the very low surface area (0.2 m2/g) of the solid-fluid interface. In contrast, the kaolinite (5-12 m2/g) data indicate a decrease of the order of 50% in the dielectric constant of the wetted matrix phase as the amount of water-wetted surface in the sample decreases. The results from this experimental study show that the presence of sorbed oil leads to a detectable change in the dielectric properties of high surface area geologic materials.
Li, Camille; Tercier, Paulette; Knight, Rosemary
Dielectric properties and microstructures for various MLCCs coated with additives
NASA Astrophysics Data System (ADS)
As electronic devices become smaller and have higher capacity, dielectric thin films are being used in the development of multilayer ceramic capacitors (MLCCs). Smaller BaTiO3 dielectric particles should be used to obtain the thickness of low dielectric layers. Further, MLCC properties are achieved through the uniform addition of various additives, but the existing method of adding nano additives has limitations. As such, this study evaluated the dielectric properties of BaTiO3 pellets after using the liquid coating method to add additives such as Dy, Mg, Mn, Cr, and Si to 150 nm BaTiO3 dielectric powder. Mn, Cr, and Si ions were each fixed at 0.1, 0.1, and 0.65 mol-%. Sintering was performed in a reducing atmosphere, and the microstructure and the dielectric properties were evaluated while varying Dy from 0.5 to 1.0 mol-% and Mg from 1.0 to 2.0 mol-%. Grain growth was observed for higher amounts of Dy, but were suppressed for higher amounts of Mg. With regards to changes in particle size, both the permittivity and the temperature coefficient of capacitance (TCC) increased with increasing particle size. The permittivity was highest for Si=0.65, Mn=0.1, Cr=0.1 Dy=0.75, and Mg=2.0 mol-%. These levels also satisfied the TCC properties of X7R. In the microstructure, the core-shell was the most developed.
Oh, Min Wook; Yeo, Dong Hun; Shin, Hyo Soon; Jeong, Dae Yong
Millimeter wave analysis of the dielectric properties of oil shales
Natural sedimentation processes give rise to fine layers in shales. If these layers alternate between organic-rich and organic-poor sediments, then the contrast in dielectric properties gives rise to an effective birefringence as the presence of hydrocarbons suppresses the dielectric constant of the host rock. We have measured these effects with a quasioptical millimeter wave setup that is rapid and noncontacting. We find that the strength of this birefringence and the overall dielectric permittivity provide two useful diagnostic of the organic content of oil shales.
John A. Scales; Michael Batzle
Radiation induced changes in electronic and dielectric properties of polyoxymethylene
First-principle calculations have been done for the Orthorhombic helical Polyoxymethylene. Electronic density of states calculation gives a value of 6.6 eV as the band gap. Phonon frequencies have been calculated at the Gamma point. Phonon modes show wave numbers ranging from 55 cm{sup -1} to 3020 cm{sup -1}. The value of Dielectric constant has been experimentally determined. The gamma irradiation of the sample causes variations in the electronic and dielectric properties of the material. Electrical conductivity increases with increase in dosage of irradiation. Percentage of crystallinity increases where as the value of dielectric constant decreases with increase in dosage of irradiation.
Sreepad, H. R.; Ravi, H. R.; Ahmed, Khaleel; Waghmare, Umesh V. [Post-Graduate Department of Physics, Government College (Autonomous), Mandya-571401 (India); Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore-560064 (India)
improved room-temperature dielectric constant. The dielectric properties of the composites under ) of the dielectric constant can be determined, where A is the area and t is the thickness of the capacitor, and q electrically actuated elastomers with strain greater than 100%. Science 287, 836┬Ł839 (2000). 6. Lehmann, W. et
Segall, Paul
Dielectric properties of silver borophosphate glasses
Dynamic behaviour of electrical conduction and polarization in silver borophosphate glasses has been studied over wide range of frequencies and temperatures. The dielectric spectrum showed a strong dispersion in C'(?) with rise in temperature which distinguishes the conduction process from a pure steady state. The observed behaviour was found to be temperature activated with an activation energy of 0.39 eV.
R. A. Hashmi; Noor-Ul Haque; N. Bano; M. K. Anis
NASA Astrophysics Data System (ADS)
Electronic and vibrational contributions to the static and dynamic (hyper)polarizability tensors of ice XI and model structures of ordinary hexagonal ice have been theoretically investigated. Calculations were carried out by the finite field nuclear relaxation method for periodic systems (FF-NR) recently implemented in the CRYSTAL code, using the coupled-perturbed Kohn-Sham approach (CPKS) for evaluating the required electronic properties. The effect of structure on the static electronic polarizabilities (dielectric constants) and second-hyperpolarizabilities is minimal. On the other hand, the vibrational contributions to the polarizabilities were found to be significant. A reliable evaluation of these (ionic) contributions allows one to discriminate amongst ice phases characterized by different degrees of proton-order, primarily through differences caused by librational motions. Transverse static and dynamic vibrational (hyper)polarizabilities were found by extrapolating calculations for slabs of increasing size, in order to eliminate substantial surface contributions.
Casassa, S.; Baima, J.; Mahmoud, A.; Kirtman, B.
Macroscopic static and dynamic mechanical properties of Yule marble
The static and dynamic tensile and compressive properties of Colorado Yule marble have been obtained from samples all secured from the same parent slab. Specimens were cored in the three principal directions of this transversely isotropic material, the axis of symmetry having been determined petrographically. Standard quasi-static and creep tests were performed, and both Hopkinson-bar and split-Hopkinson-bar tests were conducted
S. P. Howe; W. Goldsmith; J. L. Sackman
Modeling of dielectric properties of complex fluids with an equation of state.
The static permittivity is a key property for describing solutions containing polar and hydrogen bonding compounds. However, the precise relationship between the molecular and dielectric properties is not well-established. Here we show that the relative permittivity at zero frequency (static permittivity) can be modeled simultaneously with thermodynamic properties. The static permittivity is calculated from an extension of the framework developed by Onsager, Kirkwood, and Fr÷hlich to associating mixtures. The thermodynamic properties are calculated from the cubic-plus-association (CPA) equation of state that includes the Wertheim association model as formulated in the statistical associating fluid theory (SAFT) to account for hydrogen bonding molecules. We show that, by using a simple description of the geometry of the association, we may calculate the Kirkwood g-factor as a function of the probability of hydrogen bond formation. The results show that it is possible to predict the static permittivity of complex mixtures over wide temperature and pressure ranges from simple extensions of well-established theories simultaneously with the calculation of thermodynamic properties. PMID:23458349
Maribo-Mogensen, Bj°rn; Kontogeorgis, Georgios M; Thomsen, Kaj
Dielectric properties of carbon nanotubes/epoxy composites.
Material with high dielectric properties possesses the effect of energy storage and electric field homogenization, which plays an important role in the electrical and electronics domain, especially in the capacitor, electrical machinery and cable realm. In this paper, epoxy-based nanocomposites with high dielectric constant were fabricated by adding pristine and ozone functionalized multi-wall carbon nanotubes (MWCNTs). In the process-related aspect, the favorable technological parameter was obtained via reasonable arrangement and consideration of the dispersing methods including high-speed stirring and three-roller mill. As a result, a uniform dispersion status of MWCNTs in matrix has been guaranteed, which was observed by scanning and transmission electron microscopy. Meanwhile, the influence of different MWCNTs contents and diverse frequencies on the dielectric properties was compared. It was found that the dielectric constant of nano-composites decreased gradually with the increasing of frequency (10(3)-10(6) Hz). Moreover, as the content of MWCNTs increasing, the dielectric constant reached to a maximum of about 1,328 at 10(3) Hz when the pristine MWCNTs content was 0.5 wt.%. Accordingly, the DC conductivity results could interpret the peak value phenomenon by percolation threshold of MWCNTs. In addition, at the fixed content, the dielectric constant of epoxy-based nano-composites with ozone functionalized MWCNTs was lower than that of pristine ones. PMID:23646551
Peng, Jin-Ping; Zhang, Hui; Tang, Long-Cheng; Jia, Yu; Zhang, Zhong
Dielectric properties of soils as a function of moisture content
NASA Technical Reports Server (NTRS)
Soil dielectric constant measurements are reviewed and the dependence of the dielectric constant on various soil parameters is determined. Moisture content is given special attention because of its practical significance in remote sensing and because it represents the single most influential parameter as far as soil dielectric properties are concerned. Relative complex dielectric constant curves are derived as a function of volumetric soil water content at three frequencies (1.3 GHz, 4.0 GHz, and 10.0 GHz) for each of three soil textures (sand, loam, and clay). These curves, presented in both tabular and graphical form, were chosen as representative of the reported experimental data. Calculations based on these curves showed that the power reflection coefficient and emissivity, unlike skin depth, vary only slightly as a function of frequency and soil texture.
Cihlar, J.; Ulaby, F. T.
Dielectric properties of grain-grainboundary binary system
NASA Astrophysics Data System (ADS)
Dielectric properties of grain-grainboundary binary system are analyzed theoretically and compared with unary system and classical Maxwell-Wagner (MW) polarization in binary system. It is found that MW polarization appears at higher frequency compared with intrinsic polarization for grain-grainboundary binary system, which is abnormal compared with classical dielectric theory. This dielectric anomaly is premised on the existence of electronic relaxation at grainboundary. The origin of giant dielectric constant of CaCu3Ti4O12 (CCTO) ceramics is also investigated on the basis of the theoretical results. It is proposed that low frequency relaxation originates from electronic relaxation of oxygen vacancy at depletion layer, while high frequency relaxation comes from MW polarization. The results of this paper offer a quantitative identification of MW polarization from intrinsic polarization at grainboundary and a judgment of the mechanism and location of a certain polarization in grain-grainboundary binary system.
Cheng, Peng-Fei; Li, Sheng-Tao; Wang, Hui
Static and dynamic properties of stretched water
We present the results of molecular dynamics simulations of the extended simple point charge model of water to investigate the thermodynamic and dynamic properties of stretched and supercooled water. We locate the liquid¢gas spinodal, and confirm that the spinodal pressure increases monotonically with T, supporting thermodynamic scenarios for the phase behavior of supercooled water involving a ōnon-reentrantö spinodal. The dynamics
Paulo A. Netz; Francis W. Starr; H. Eugene Stanley; Marcia C. Barbosa
NASA Technical Reports Server (NTRS)
The diurnal characteristics of microwave dielectric properties and water potential of two conifer species were investigated in July and September, 1990. P-band and C-band radial dielectric profiles of hemlock and red spruce, as well as hemlock diurnal water potential and dielectric profiles, are presented. The resulting radial dielectric profiles matched the regions of the functional sapwood (water transport component of the active xylem) in both species such that the sapwood was characterized by a higher dielectric than the bark and heartwood tissues. This is probably due to characteristic differences in the water content of each tissue. As the hemlocks progressed through their diurnal water potential pattern, the dielectric profile remained static until mid-afternoon. As the tension in the water column relaxed (2 to 3 bars) the dielectric constant decreased by 30 to 40 percent. There are several possible explanations for this phenomenon, and these may relate to the dependency of the dielectric measurements on temperature, salinity, and volumetric water content.
Salas, W. A.; Ranson, K. J.; Rock, B. N.; Moss, D. M.
Pyroelectric and dielectric properties of calcium barium niobate single crystals
NASA Astrophysics Data System (ADS)
The effect of the calcium concentration on the pyroelectric and dielectric properties of Ca x Ba1 - x Nb2O6 (CBN) crystals has been studied over a wide temperature range. It has been shown that the calcium concentration only influences the Curie point of crystals of this class. It insignificantly changes the absolute values of the permittivity, the coercive field, and the remanent polarization and does not influence their temperature dependences and the shape of the dielectric hysteresis loop. The possibility of the existence of relaxor properties in CBN crystals has been discussed.
Malyshkina, O. V.; Lisitsin, V. S.; Dec, J.; ?ukasiewicz, T.
High field dielectric properties of anisotropic polymer-ceramic composites
Using dielectrophoretic assembly, we create anisotropic composites of BaTiO{sub 3} particles in a silicone elastomer thermoset polymer. We study a variety of electrical properties in these composites, i.e., permittivity, dielectric breakdown, and energy density as function of ceramic volume fraction and connectivity. The recoverable energy density of these electric-field-structured composites is found to be highly dependent on the anisotropy present in the system. Our results indicate that x-y-aligned composites exhibit higher breakdown strengths along with large recoverable energy densities when compared to 0-3 composites. This demonstrates that engineered anisotropy can be employed to control dielectric breakdown strengths and nonlinear conduction at high fields in heterogeneous systems. Consequently, manipulation of anisotropy in high-field dielectric properties can be exploited for the development of high energy density polymer-ceramic systems.
Tomer, V.; Randall, C. A. [Center of Dielectric Studies, Materials Research Institute, Materials Research Laboratory Bldg., Pennsylvania State University, Pennsylvania 16802I (United States)
The Effect of Crystal Forms on Dielectric Properties of Polypropylene
In the present paper, the dielectric properties of polypropylenes with different crystal forms were investigated. The space charge distribution was measured by using electro-acoustic pulse and the effect of space charge on short circuit breakdown was analyzed by using DC pre-stress voltage. Relative crystallinity of the beta crystal in beta crystal form polypropylenes was analyzed by using DSC, and morphology
Hong Zhao; Mingzhong Xu; wenlong Zhang; Xuan Wang
Mechanical and Dielectric Breakdown Properties of Biodegradable Plastics
The mechanical and dielectric breakdown properties of polylactic acid (PLA), which is a biodegradable plastic, were examined, and a physicochemical analysis was performed. At room temperature, the tensile strength of PLA was about 100 MPa, almost the same as for PP, but at 100░C, even the value for LDPE decreased. The Young's modulus of PLA at room temperature was about
Katsuyoshi Shinyama; Shigetaka Fujita
Electrical Conduction and Dielectric Properties of Biodegradable Plastics
We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60░C and the melting point (Tm) was about 166░C. For the temperature dependence of current density (J), J of PLA
Katsuyoshi Shinyama; Shigetaka Fujita
Dielectric properties of biodegradable polylactic acid and starch ester
In order to examine the applicability of biodegradable polymers to the fields of electrical insulation, several dielectric properties of two typical biodegradable polymers, polylactic acid (PLA) and starch ester (SE), are examined. A fairly larger amount of space charge is accumulated in both polymers in comparison to low-density polyethylene (LDPE). This seems partly due to the presence of hydroxyl and
N. Hirail; Y. Maeno; H. Tamura; D. Kaneko; T. Tanaka; Y. Ohki; Y. Tajitsu; M. Kohtoh; S. Okabe
NASA Astrophysics Data System (ADS)
The electromagnetic properties of dielectric-conductor mixtures are investigated and the validity of several 'mixture laws' is discussed. Wideband microwave absorption can not be performed by means of homogeneous materials. Experimentally, it was noticed that some compounds made with small conducting grains dipersed in a dielectric host can be used in radar absorber design. Many 'mixture laws' were derived to model the dielectric permittivity of dielectric conductor mixtures. Though they give good results for mixtures in which grains are separated, they fail in modeling those in which there exist conducting paths between inclusions. If the paths are tunneling junctions, the mixtures are called 'supercolative'. Electron jumping is responsible for special phenomena: an anomalous direct current conduction threshold; and a 'Jonscher effect' caused by short electrostatic interactions. The mixtures for which the quasi static approximation is not matched inside the conducting medium are considered. It yields an artificial lossy diamagnetic behavior for which a model is derived. Experimental results that show very good agreements with this model are presented. This special effect gives rise to a new method for measuring the electrical conductivity of grain in conducting powders.
Guillot, Thierry
Dielectric and pyroelectric properties of ultrathin, monocrystalline lithium tantalate
NASA Astrophysics Data System (ADS)
Ultrathin, self-supporting lithium tantalate (LiTaO3) wafers have been fabricated out of a single crystal with a minimum thickness of about 0.4 ?m using ion-beam milling. The most decisive parameters (pyroelectric coefficient, relative permittivity, and dielectric loss factor) for their use in pyroelectric radiation detectors were studied in dependence on film thickness and temperature. The potential performance of pyroelectric materials was evaluated using appropriate figures of merit. In addition, the dielectric and pyroelectric properties of stoichiometric LiTaO3 were investigated and compared to congruent LiTaO3 bulk material conventionally used for pyroelectric detectors.
Schossig, Marco; Norkus, Volkmar; Gerlach, Gerald
Dielectric properties of Ba2YMoO6 ceramics
NASA Astrophysics Data System (ADS)
Double-perovskite Ba2YMoO6 ceramics were prepared via the solid-state reaction route. Their dielectric properties were investigated as a function of temperature (100 ░C?T?800 ░C) and frequency (300 Hz?f?5 MHz). In the temperature below 600 ░C, two thermally activated dielectric relaxations can be well identified. The low-temperature relaxation was ascribed to be a dipolar relaxation caused by oxygen vacancy diffusion, and the high-temperature relaxation is found to be a Maxwell-Wagner relaxation due to surface-layer effect.
Li, Qiuju; Ren, Jun; Cui, Jiangyu; Yu, Yi; Zhang, Jian; Wang, Chunchang
Amorphous aluminum oxynitride (AlON) possesses unique properties of high dielectric strength, high resistivity, low loss, high decomposition temperature, chemical inertness, and high thermal conductivity. These properties make it a candidate for a next generation capacitor dielectric. DC pulsed magnetron reactive sputtering is used to produce amorphous AlON films on various substrates. Dielectric properties are optimized by adjusting DC power, pulse
K. R. Bray; R. L. C. Wu; S. Fries-Carr; J. Weimer
Electrical conductivity and dielectric property of fly ash geopolymer pastes
NASA Astrophysics Data System (ADS)
The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were studied. The effects of the liquid alkali solution to ash ratios (L/A) were analyzed. The mineralogical compositions and microstructures of fly ash geopolymer materials were also investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The 10 mol sodium hydroxide solution and sodium silicate solution at a sodium silicate-to-sodium hydroxide ratio of 1.0 were used in making geopolymer pastes. The pastes were cured at 40░C. It is found that the electrical conductivity and dielectric constant are dependent on the frequency range and L/A ratios. The conductivity increases but the dielectric constant decreases with increasing frequency.
Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin
Static, statistical, and dynamical properties of small sodium clusters
This paper reports results obtained in the study of small alkali metal clusters (2=n=34). Properties of interest include static descriptions of the Potential Energy Surfaces (PES) using a Distance-Dependent Tight Binding hamiltonian (DDTB) and new results obtained with the same hamiltonian through a Monte-Carlo Growth Method (MCGM) which is shown to give an efficient way to sample the PES, but
R. Poteau; D. Maynau; J.-P. Daudey; F. Spiegelmann
Technique for Performing Dielectric Property Measurements at Microwave Frequencies
NASA Technical Reports Server (NTRS)
A paper discusses the need to perform accurate dielectric property measurements on larger sized samples, particularly liquids at microwave frequencies. These types of measurements cannot be obtained using conventional cavity perturbation methods, particularly for liquids or powdered or granulated solids that require a surrounding container. To solve this problem, a model has been developed for the resonant frequency and quality factor of a cylindrical microwave cavity containing concentric cylindrical samples. This model can then be inverted to obtain the real and imaginary dielectric constants of the material of interest. This approach is based on using exact solutions to Maxwell s equations for the resonant properties of a cylindrical microwave cavity and also using the effective electrical conductivity of the cavity walls that is estimated from the measured empty cavity quality factor. This new approach calculates the complex resonant frequency and associated electromagnetic fields for a cylindrical microwave cavity with lossy walls that is loaded with concentric, axially aligned, lossy dielectric cylindrical samples. In this approach, the calculated complex resonant frequency, consisting of real and imaginary parts, is related to the experimentally measured quantities. Because this approach uses Maxwell's equations to determine the perturbed electromagnetic fields in the cavity with the material(s) inserted, one can calculate the expected wall losses using the fields for the loaded cavity rather than just depending on the value of the fields obtained from the empty cavity quality factor. These additional calculations provide a more accurate determination of the complex dielectric constant of the material being studied. The improved approach will be particularly important when working with larger samples or samples with larger dielectric constants that will further perturb the cavity electromagnetic fields. Also, this approach enables the ability to have a larger sample of interest, such as a liquid or powdered or granulated solid, inside a cylindrical container.
Barmatz, Martin B.; Jackson, Henry W.
in the experimentally detected dielectric response of organic semi- conductor copper phthalocyanine. While a giantIntrinsic dielectric properties and charge transport in oligomers of organic semiconductor copper. Huang and Q. M. Zhang Electrical Engineering Department and Materials Research Institute
Bobnar, Vid
Dielectric properties of anodic oxide films on tantalum
The electrochemical behaviour of Ta-TaOx structures was investigated by impedance spectroscopy. It was shown that, after the polishing treatment, the electrode is covered by an ōinitialö oxide film containing tantalum monoxide, TaO, and that ōelectrogeneratedö oxides are only composed of tantalum pentoxide, Ta2O5 (? 97 mol%). However, the dielectric properties of the structures strongly depend on the thickness of the
O. Kerrec; D. Devilliers; H. Groult; M. Chemla
Multiferroic laminated composites consisting of lead-zirconate titanate (PZT)\\/polyvinylidene-fluoride (PVDF) particulate composite layers and Tb-Dy-Fe alloy (Terfenol-D)\\/PVDF particulate composite layers, prepared by a simple hot-molding technique, were reported. In the laminated composites, the polymer PVDF is inert and used just as a binder. The measured dielectric, ferroelectric, magnetic, and magnetoelectric properties demonstrate strong dependence on volume fraction f of the PVDF
N. Cai; J. Zhai; C.-W. Nan; Y. Lin; Z. Shi
Dielectric and structural properties of aqueous nonpolar solute mixtures
NASA Astrophysics Data System (ADS)
The dielectric properties and molecular structure of water mixtures with different nonpolar solutes (methane and noble gases) are studied using molecular dynamics. The water-water, water-solute, and solute-solute interactions are calculated using the combination of a polarizable potential [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys. 127, 154509 (2007), 10.1063/1.2786449] for water plus the Lennard-Jones potential. The effect of solute size and concentration on the solubility of the system, hydrogen bonding, dielectric constant, and dipole moment are investigated over a temperature range of 278-750 K and solute percentage mole fractions up to 30%. Solute particles affect the structure of water, resulting in the compression of oxygen-oxygen and oxygen-hydrogen radial distribution functions. The influence of the solute extends both to relatively low concentrations and high temperatures. The coordination numbers of aqueous solutions of the nonpolar solutes appear to be proportional to the size of the solute particles. Our study shows the destructive influence of the nonpolar solute on both the tetrahedral water structure and hydrogen bond formation at solute concentrations greater than 30%. The presence of nonpolar particles typically decreases both the dielectric constant and dipole moment. The decrease of dielectric constant and water dipole moment is directly proportional to the solute concentration and temperature.
Shvab, I.; Sadus, Richard J.
Dielectric surface plasmon Bragg mirrors: theory, design, and properties
NASA Astrophysics Data System (ADS)
Surface plasmon based photonic devices are promising candidates for highly integrated optics. An important effort in the development of these devices is dedicated to the design of systems allowing the two dimensional control of surface plasmon (SPP) propagation. Recently, it has been shown that Bragg mirrors consisting of gratings of metallic lines or indentations on a metallic surface are very efficient tools to perform this task. Alternatively, using structured dielectric layers on top of the metallic layer to build SPP optical elements based on the effective refractive index contrast has been lately demonstrated. This kind of elements relies on the same principles as conventional optical elements. Here we analyze the ability of gratings of dielectric ridges deposited on a metallic layer to act as dielectric SPP Bragg mirrors. The dispersion relation of these systems shows the presence of a gap whose position can be approximately predicted by the same relation as for standard optical Bragg mirrors. The properties of these dielectric based SPP Bragg mirrors have been examined as a function of several structural grating parameters. The obtained results have been experimentally confirmed by means of Fourier plane leakage radiation microscopy.
Randhawa, Sukanya; Gonzßlez, MarĒa Ujuķ; Renger, Jan; Weeber, Jean-Claude; Quidant, Romain
Static and dynamic properties of the classical XY chain
NASA Astrophysics Data System (ADS)
We present results for the static and dynamic behavior of a one-dimensional classical XY chain. Equilibrium configurations are produced by an importance-sampling Monte Carlo method. Static properties are evaluated from these data and a spin-dynamics method is then used to evaluate time-displaced correlation functions and to calculate the scattering function S(q,?). The transverse spin-spin correlation functions decay exponentially for large times. The longitudinal spin-spin correlation functions show oscillatory behavior, especially at low temperatures. The longitudinal-scattering function displays spin-wave peaks, and the transverse-scattering function shows central peaks (relaxational behavior) which change to fluctuation-broadened spin-wave peaks for large values of q?. The energy-energy correlation function shows diffusive behavior for high temperatures and non-diffusive behavior for low temperatures.
Gerling, R. W.; Landau, D. P.
Dielectric properties of 'diamondlike' carbon prepared by RF plasma deposition
NASA Technical Reports Server (NTRS)
Metal-carbon-metal structures were fabricated using either gold or aluminum evaporated electrodes and RF plasma (methane) deposited 'diamondlike' carbon films. Alternating-current conductance and capacitance versus voltage and frequency (10 Hz to 13 MHz) data were taken to determine the dielectric properties of these films. Conductance versus frequency data fit a generalized power law, consistent with both dc and hopping conduction components. The capacitance versus frequency data are well matched to the conductance versus frequency data, as predicted by a Kramers-Kronig analysis. The dielectric loss tangent is nearly constant at 0.5 to 1.0 percent over the frequency range from 1 to 100 kHz. The dc resistivity is above 10 to the 13th ohm cm, and the dc breakdown strength is above 8 x 10 to the 6th V/cm is properly prepared samples.
Lamb, J. D.; Woollam, J. A.
Mechanism Underlying Stacking-Layer Effect of Dielectric Properties of Multilayer Ceramic Capacitors
NASA Astrophysics Data System (ADS)
The stacking-layer effect in multilayer ceramic capacitors (MLCCs) is a phenomenon in which the dielectric permittivity of dielectric layers increases with increasing number of layers. To elucidate the mechanism underlying this effect, we performed a simulation of residual stress in MLCCs by the finite element method (FEM) as well as dielectric measurements under uniaxial compressive stress. The FEM analysis revealed that tensile stress along the stacking direction was induced in dielectric layers owing to the difference in thermal expansion coefficient between internal electrodes and dielectric layers. The results of dielectric measurements indicated that the shell part in the dielectrics of MLCCs played an important role in the stress dependence of dielectric properties. The mechanism underlying the stacking-layer effect proposed in this study was based on the enhancement of polarization rotations in polar nanoregions in the relaxor by the tensile stress in dielectric layers.
Yokomizo, Satoshi; Hoshina, Takuya; Takeda, Hiroaki; Taniguchi, Katsuya; Mizuno, Youichi; Chazono, Hirokazu; Tsurumi, Takaaki
--aimed at shedding light on the behavior of dielectric elastomer composites--have been recently reported demonstrated that dielectric elastomer composites--comprising, in essence, a mechanically soft matrix of lowSome simple explicit results for the elastic dielectric properties and stability of layered
Lopez-Pamies, Oscar
NASA Astrophysics Data System (ADS)
We report first-principles study of structural, electronic, vibrational, dielectric, and elastic properties of Ba2YTaO6, a pinning material in high temperature superconductors (HTS), by using density functional theory. By using different exchange-correlation potentials, the accuracy of the calculated lattice constants of Ba2YTaO6 has been achieved with GGA-RPBE, since many important physical quantities crucially depend on change in volume. We have calculated the electronic band structure dispersion, total and partial density of states to study the band gap origin and found that Ba2YTaO6 is an insulator with a direct band gap of 3.50 eV. From Mulliken population and charge density studies, we conclude that Ba2YTaO6 have a mixed ionic-covalent character. Moreover, the vibrational properties, born effective charges, and the dielectric permittivity tensor have been calculated using linear response method. Vibrational spectrum determined through our calculations agrees well with the observed Raman spectrum, and allows assignment of symmetry labels to modes. We perform a detailed analysis of the contribution of the various infrared-active modes to the static dielectric constant to explain its anisotropy, while electronic dielectric tensor of Ba2YTaO6 is nearly isotropic, and found that static dielectric constant is in good agreement with experimental value. The six independent elastic constants were calculated and found that tetragonal Ba2YTaO6 is mechanically stable. Other elastic properties, including bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and elastic anisotropy ratios are also investigated and found that Poisson's ratio and Young's modulus of Ba2YTaO6 are similar to that of other pinning materials in HTS.
Ganeshraj, C.; Santhosh, P. N.
Static properties of nuclear matter within the Boson Loop Expansion
The use of the Boson Loop Expansion is proposed for investigating the static properties of nuclear matter. We explicitly consider a schematic dynamical model in which nucleons interact with the scalar-isoscalar sigma meson. The suggested approximation scheme is examined in detail at the mean field level and at the one- and two-loop orders. The relevant formulas are provided to derive the binding energy per nucleon, the pressure and the compressibility of nuclear matter. Numerical results of the binding energy at the one-loop order are presented for Walecka's sigma-omega model in order to discuss the degree of convergence of the Boson Loop Expansion.
W. M. Alberico; R. Cenni; G. Garbarino; M. R. Quaglia
The dielectric properties of water within model transbilayer pores.
Ion channels contain extended columns of water molecules within their transbilayer pores. The dynamic properties of such intrapore water have been shown to differ from those of water in its bulk state. In previous molecular dynamics simulations of two classes of model pore (parallel bundles of Ala20 alpha-helices and antiparallel barrels of Ala10 beta-strands), a substantially reduced translational and rotational mobility of waters was observed within the pore relative to bulk water. Molecular dynamics simulations in the presence of a transpore electrostatic field (i.e., a voltage drop along the pore axis) have been used to estimate the resultant polarization (due to reorientation) of the intrapore water, and hence to determine the local dielectric behavior within the pore. It is shown that the local dielectric constant of water within a pore is reduced for models formed by parallel alpha-helix bundles, but not by those formed by beta-barrels. This result is discussed in the context of electrostatics calculations of ion permeation through channels, and the effect of the local dielectric of water within a helix bundle pore is illustrated with a simple Poisson-Boltzmann calculation. Images FIGURE 1 PMID:9370434
Sansom, M S; Smith, G R; Adcock, C; Biggin, P C
Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites
Particulate composites of ferrite and ferroelectric phases with xNiFe{sub 2}O{sub 4} (NF) and (1 - x)Pb{sub 0.988}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.976}Nb{sub 0.024}O{sub 3} (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 Degree-Sign C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.
Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana [Faculty of Physics, 'Al. I. Cuza' University of Iasi 700506, Iasi (Romania); Airimioaei, Mirela [Faculty of Chemistry, 'Al. I. Cuza' University of Iasi 700506, Iasi, Romania and Dept. Chemistry and Process Engineering, University of Genoa, P-le Kennedy no. 1, I-16129, Genoa (Italy); Tascu, Sorin [RAMTECH Faculty of Physics, 'Al. I. Cuza' University of Iasi 700506 (Romania); Schileo, Giorgio [Christian Doppler Laboratory for Advanced Ferroic Oxides, Sheffield Hallam University, Howard Street, Sheffield S1 1WB (United Kingdom); Galassi, Carmen [CNR-ISTEC, Via Granarolo no. 64, I-48018 Faenza (Italy)
Soft Actuator for Robotic Applications Based on Dielectric Elastomer: Quasi-Static Analysis
In this paper a new soft actuator based on dielectric elastomer is proposed. The actuator, called an antagonistically-driven linear actuator (ANTLA), has the muscle-like characteristics capable of performing the motions such as forward\\/backward\\/controllable compliance. Due to its simplicity of configuration and ease of fabrication, it has the advantage to be scale-independently implemented in meso- or micro-scale robotic applications. Its basic
Hyoukryeol Choi; Sungmoo Ryew; K. M. Jung; H. M. Kim; Jae Wook Jeon; Jea-do Nam; Ryutaro Maeda; Kazuo Tanie
Static Properties of the Multiple-Sine-Gordon Systems
In this paper, we examine some basic properties of the multiple-Sine-Gordon (MSG) systems, which constitute a generalization of the celebrated sine-Gordon (SG) system. We start by showing how MSG systems can be viewed as a general class of periodic functions. Next, periodic and step-like solutions of these systems are discussed in some details. In particular, we study the static properties of such systems by considering slope and phase diagrams. We also use concepts like energy density and pressure to characterize and distinguish such solutions. We interpret these solutions as an interacting many body system, in which kinks and antikinks behave as extended particles. Finally, we provide a linear stability analysis of periodic solutions which indicates short wavelength solutions to be stable.
M. Peyravi; N. Riazi; Afshin Montakhab
Dielectric and Thermal Properties of Rice Cake Formulations Containing Different Gums Types
In this study, dielectric properties of rice cake formulations containing different gum types (xanthan, guar, locust bean, HPMC, and kappa-carrageenan) were determined at temperatures between 25 and 90░C at 2450 MHz. Moreover, thermal properties of these formulations were determined by using differential scanning calorimeter (DSC). Dielectric properties of cake batters were found to be dependent on cake formulation. Xanthan and
Elif Turabi; Marc Regier; Gulum Sumnu; Serpil Sahin; Matthias Rother
Dielectric properties of carbon nanotube\\/silicone elastomer composites
Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to mechanical work. Their large strains and conformability make them enticing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators should have a high dielectric constant and high dielectric breakdown strength.
Zhen Zhang; Shouhua Sun; Liwu Liu; Kai Yu; Yanju Liu; Jinsong Leng
NASA Astrophysics Data System (ADS)
We present a novel approach to evaluate quasi particle energies within many body perturbation theory, that substantially improves both the computational efficiency and the numerical accuracy of existing techniques.ootnotetextHuy-Viet Nguyen, T. Anh Pham, D. Rocca and G. Galli (preprint). We use a spectral decomposition of the static dielectric matrix as a basis for the frequency dependent density-density response function, and density functional perturbation theory to avoid the explicit calculation of empty electronic states. A Lanczos-chain algorithm is employed that allows for the evaluation of spectra over a wide frequency range. The numerical accuracy of computed quasi particle energies is controlled by a single parameter. The efficiency and accuracy of our approach are demonstrated by computing vertical ionization potentials and electron affinities of several molecules and diamondoids. Our results are in good agreement with experiment and those reported in the literature using Quantum Monte Carlo calculations.
Pham, T. Anh; Nguyen, Huy-Viet; Rocca, Dario; Galli, Giulia
Static and dynamic properties of a reversible gel
We study a microscopically realistic model of a physical gel and use computer simulations to investigate its static and dynamic properties at thermal equilibrium. The phase diagram comprises a sol phase, a coexistence region ending at a critical point, a gelation line, and an equilibrium gel phase unrelated to phase separation. The global structure of the gel is homogeneous, but the stress is supported by a fractal network. Gelation results in a dramatic slowing down of the dynamics, which can be used to locate the transition, which otherwise shows no structural signatures. Moreover, the equilibrium gel dynamics is highly heterogeneous as a result of the presence of particle families with different mobilities. An analysis of gel dynamics in terms of mobile and arrested particles allows us to elucidate several differences between the dynamics of equilibrium gels and that of glass-formers.
Pablo I. Hurtado; Pinaki Chaudhuri; Ludovic Berthier; Walter Kob
Effect of dielectric properties of metals on terahertz transmission in subwavelength hole arrays
of subwavelength hole arrays at THz frequencies. Extraordinary trans- mission at two pronounced surface plasmon ┬▒1Effect of dielectric properties of metals on terahertz transmission in subwavelength hole arrays of dielectric function of metals on the transmission properties of terahertz pulses through periodically
Mechanical properties of dielectric elastomer actuators with smart metallic compliant electrodes
Dielectric elastomer actuator technology is based on electric field induced deformation. From the viewpoint of materials technology, many points must be addressed, among which are material dielectric properties, breakdown voltage, viscoelastic losses and elastomer spring mechanical properties. From the viewpoint of actuator manufacturing, we will mention elastomer thin film and fiber processing as well as compliant electrode design. However, among
Mohammed Benslimane; Peter Gravesen; Peter Sommer-Larsen
Structural and Dielectric Properties of Quartz-Water Interfaces
The structure, orientation, and dielectric of water at the quartz|water interface has been examined under different hydration levels using classical molecular dynamics. The properties of 1H?O/10 ┼▓, 2H?O/10 ┼▓, 4H?O/10 ┼▓, and bulk water on quartz have been benchmarked against experimental data. Structurally, the simulations match existing sum-frequency spectroscopy data, which indicate the existence and orientation of both frozen and loosely bound water on the quartz surface. Good agreement has also been found with existing experimental dielectric data for the 1H?O/10 ┼▓ level of hydration, and a clear difference has been found in the values of ?s = 48, ?| = 48, and ?? = 40 for the first slice of a bulk-water-solid interface and ?s= 30, ?| = 30, and ?? = 10 for that of 1H?O/10 ┼▓ water coverage. Overall there is a fundamental difference in shielding between a single interface and the 1H?O/10 ┼2 level of hydration.
Wander, Matthew C.; Clark, Aurora E.
NASA Astrophysics Data System (ADS)
We report structural, magnetic, and dielectric properties of oxygen deficient hexagonal BaFeO3-?. A large dielectric permittivity comparable to that of other semiconducting oxides is observed in BaFeO3-?. Magnetization measurements indicate magnetic inhomogeneity and the system shows a paramagnetic to antiferromagnetic transition at ś160 K. Remarkably, the temperature, at which paramagnetic to antiferromagnetic transition occurs, around this temperature, a huge drop in the dissipation factor takes place and resistivity shoots up; this indicates the possible correlation among magnetic and dielectric properties. First principle simulations reveal that some of these behaviors may be explained in terms of many body electron correlation effect in the presence of oxygen vacancy present in BaFeO3-? indicating its importance in both fundamental science as well as in applications.
Sagdeo, Archna; Gautam, Kamini; Sagdeo, P. R.; Singh, M. N.; Gupta, S. M.; Nigam, A. K.; Rawat, Rajeev; Sinha, A. K.; Ghosh, Haranath; Ganguli, Tapas; Chakrabarti, Aparna
NASA Astrophysics Data System (ADS)
The (NH4)2S treatment can reduce native oxides and passivate GaAs. Atomic layer-deposited Al2O3 can further remove the residue native oxides by self-cleaning. Stacked with high dielectric constant TiO2 prepared by atomic layer deposition on Al2O3/(NH4)2S-treated GaAs MOS capacitor, the leakage current densities can reach 4.5 ū 10-8 and 3.4 ū 10-6 A/cm2 at ▒2 MV/cm. The net effective dielectric constant of the entire stack is 18 and the interface state density is about 4.2 ū 1011/cm2/eV. The fabricated enhancement-mode n-channel GaAs MOSFET exhibited good electrical characteristics with a maximum g m of 122 mS/mm and electron mobility of 226 cm2/V s.
Lee, Ming-Kwei; Yen, Chih-Feng
Magnetic properties and dielectric behavior in ferrite/ferroelectric particulate composites
NASA Astrophysics Data System (ADS)
Particulate composites of ferrite and ferroelectric phases having the general formula ( x)BaTiO 3+(1- x)Ni 0.92Co 0.03Cu 0.05Fe 2O 4 (where x is mole fraction of components that varies as 0.85, 0.70 and 0.55) were prepared by conventional double-sintering ceramic method. The presence of constituent phases was confirmed by X-ray diffraction (XRD) technique. The average grain size was determined by using scanning electron micrographs. The variation of dielectric constant and tan ? with frequency in the range 20 Hz-1 MHz was studied. The variation of loss tangent (tan ?) and dielectric constant with temperature at fixed frequencies of 1 kHz, 10 kHz, 100 kHz and 1 MHz was also studied. The saturation magnetization ( Ms) and magnetic moment ( ?B in Bohr magnetons) are reported for all composites. The static magnetoelectric (ME) voltage coefficient was measured as a function of intensity of applied DC magnetic field. The changes were observed in dielectric properties as well as in ME output with variation in molar fraction of constituent phases. A maximum ME conversion factor of 538.59 ?V/cm G was observed for the composites with 70% BaTiO 3+30% Ni 0.92Co 0.03Cu 0.05Fe 2O 4. The present ME composites may be useful in preparing devices such as magnetic sensors and cables, etc.
Devan, R. S.; Chougule, B. K.
Testing techniques for determining static mechanical properties of Pneumatic tires
NASA Technical Reports Server (NTRS)
Fore-aft, lateral, and vertical spring rates of model and full-scale pneumatic tires were evaluated by testing techniques generally employed by industry and various testing groups. The purpose of this experimental program was to investigate what effects the different testing techniques have on the measured values of these important static tire mechanical properties. The testing techniques included both incremental and continuous loadings applied at various rates over half, full, and repeated cycles. Of the three properties evaluated, the fore-aft stiffness was demonstrated to be the most affected by the different testing techniques used to obtain it. Appreciable differences in the fore-aft spring rates occurred using both the increment- and continuous-loading techniques; however, the most significant effect was attributed to variations in the size of the fore-aft force loop. The dependence of lateral stiffness values on testing techniques followed the same trends as that for fore-aft stiffness, except to a lesser degree. Vertical stiffness values were found to be nearly independent of testing procedures if the nonlinear portion of the vertical force-deflection curves is avoided.
Dodge, R. N.; Larson, R. B.; Clark, S. K.; Nybakken, G. H.
Characterization of concrete properties from dielectric properties using ground penetrating radar
This paper presents the experimental results of a study of the relationships between light-weight (LWAC) and normal aggregate concrete (NAC) properties, as well as radar wave properties that are derived by using ground penetrating radar (GPR). The former (LWAC) refers to compressive strength, apparent porosity and saturated density, while the latter (NAC) refers to real part of dielectric permittivity ({epsilon}' or real permittivity) and wave energy level (E). Throughout the test period of the newly cast concrete cured for 90 days, the above mentioned material properties gradually changed which can be attributed to the effects of cement hydration, different types of aggregates and initial water to binder ratios. A number of plots describing various properties of concrete such as dielectric, strength and porosity perspectives were established. From these plots, we compare the characteristics of how much and how fast free water was turned to absorbed water in LWAC and NAC. The underlying mechanisms and a mechanistic model are then developed.
Lai, W.L.; Kou, S.C. [Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Tsang, W.F. [Department of Building and Real Estate, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Poon, C.S. [Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)], E-mail: email@example.com
Dielectric properties of betaine phosphite and deuterated betaine phosphite films
NASA Astrophysics Data System (ADS)
Polycrystalline films of betaine phosphite (BPI) and deuterated BPI have been grown by evaporation on LiNbO3, ?-SiO2, ?-Al2O3, and NdGaO3 substrates. These films consist of large single-crystal blocks in which the polar axis ( b) lies in the substrate plane. The results of studying the dielectric properties of the films using interdigital electrodes, X-ray diffraction, and block images in a polarized-light microscope in reflection are reported. The film transition into the ferroelectric state at T = T c is accompanied by strong anomalies of the capacitance of the film/interdigital structure/substrate structure. The deuteration of BPI films leads to an increase in their temperature T c: from T c = 200 K for BPI-based structures to T c = 280 K for structures with a high degree of deuteration ( d ś 90%).
Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Pankova, G. A.; Frederiks, I. D.; Lemanov, V. V.
A spherical model with directional interactions: I. Static properties
We introduce a simple spherical model whose structural properties are similar to the ones generated by models with directional interactions, by employing a binary mixture of large and small hard spheres, with a square-well attraction acting only between particles of different size. The small particles provide the bonds between the large ones. With a proper choice of the interaction parameters, as well as of the relative concentration of the two species, it is possible to control the effective valence. Here we focus on a specific choice of the parameters which favors tetrahedral ordering and study the equilibrium static properties of the system in a large window of densities and temperatures. Upon lowering the temperature we observe a progressive increase in local order, accompanied by the formation of a four-coordinated network of bonds. Three different density regions are observed: at low density the system phase separates into a gas and a liquid phase; at intermediate densities a network of fully bonded particles develops; at high densities -- due to the competition between excluded volume and attractive interactions -- the system forms a defective network. The very same behavior has been previously observed in numerical studies of non-spherical models for molecular liquids, such as water, and in models of patchy colloidal particles. Differently from these models, theoretical treatments devised for spherical potentials, e.g. integral equations and ideal mode coupling theory for the glass transition can be applied in the present case, opening the way for a deeper understanding of the thermodynamic and dynamic behavior of low valence molecules and particles.
Emanuela Zaccarelli; Francesco Sciortino; Piero Tartaglia
Dielectric properties of carbon nanotube/silicone elastomer composites
NASA Astrophysics Data System (ADS)
Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to mechanical work. Their large strains and conformability make them enticing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators should have a high dielectric constant and high dielectric breakdown strength. Here we have investigated the increase in permittivity of a commercial silicone elastomer by the addition of carbon nanotube. The percolation threshold of the composites is obtained to be low. Experimental results suggest that for the case of conductive filler particle-elastomer matrix interaction, actuation strain increases with increasing carbon nanotube content.
Zhang, Zhen; Sun, Shouhua; Liu, Liwu; Yu, Kai; Liu, Yanju; Leng, Jinsong
to study gases,2 semiconductors,3 super- conductors,4 dielectrics,5 nonpolar liquids,6 and water.7 WeFar-Infrared Dielectric Properties of Polar Liquids Probed by Femtosecond Terahertz Pulse (), over the frequency range from 2 to 50 cm-1 for water, methanol, ethanol, 1-propanol, and liquid ammonia
NASA Astrophysics Data System (ADS)
Polymer based composites with high dielectric constant and low dielectric loss were fabricated by dispersing core-shell structured carbon/silica nanohybrid (CS) into a poly (vinylidene fluoride) (PVDF) matrix. Due to the high conductive carbon core, nonconductive silica shell and the good dispersion of the CS fillers in PVDF, the CS/PVDF composites exhibited better dielectric properties than most nano-carbon materials/polymer composites. These experimental results can be understood by the percolation theory and microcapacitor model. Our strategy provides a pathway to achieve nano-carbon materials/polymer composites with good dielectric performances.
Lei, Tuo; Xue, Qingzhong; Chu, Liangyong; Han, Zhide; Sun, Jin; Xia, Fujun; Zhang, Zhongyang; Guo, Qikai
Coupling between magnetism and dielectric properties in quantum paraelectric EuTiO3
NASA Astrophysics Data System (ADS)
The dielectric constant of quantum paraelectric EuTiO3, which contains Eu2+ with S=7/2 spin and Ti4+, has been measured under a magnetic field. The dielectric constant shows a critical decrease at the antiferromagnetic ordering of the Eu spins at 5.5 K, as well as a substantial change under a magnetic field (by ~7% with 1.5 T), indicating a strong coupling between the Eu spins and dielectric properties. We show that the variation of the dielectric constant is dominated by the pair correlation of the nearest-neighbor Eu spins, likely via the variation of the soft-phonon-mode frequency.
Katsufuji, T.; Takagi, H.
NASA Astrophysics Data System (ADS)
The particulate composite materials of ferrite-ferroelectric ceramics viz. nickel-cobalt-copper ferrite (i.e., Ni0.94Co0.01Cu0.05Fe2O4) and barium titanate were synthesized by the double sintering ceramic technique. The presence of constituent phases in the composites was confirmed by x-ray diffraction studies. The average grain size was calculated by using a scanning electron micrograph. The electrical properties such as dc resistivity and thermo-emf were measured as a function of temperature and volume fraction of constituent phases. The ac conductivity was calculated from dielectric data in the frequency range from 100Hzto1MHz. It is concluded that the conduction in the present composites is due to small polarons. The relative dielectric constant measured as a function of applied frequency varies with the variation in the dc resistivity and molar fraction of constituent phases. It shows dispersion in the lower frequency range. The hysteresis behavior was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (?B). The static magnetoelectric (ME) voltage coefficient was measured as a function of applied dc magnetic field. It increases first and then falls down with increasing magnetic field. The variation in ME response has been explained in terms of content of ferrite phase, resistivity of composites, and intensity of magnetic field. The maximum ME conversion factor of 637?V/cmOe was observed for the composite with 30% Ni0.94Co0.01Cu0.05Fe2O4+70% BaTiO3. These composites may be useful as phase shifters, magnetic sensors, cables, etc.
Devan, R. S.; Chougule, B. K.
The interface between the polymer and the particle has a critical role in altering the properties of a composite dielectric. Polymer-ceramic nanocomposites are promising dielectric materials for many electronic and power devices, combining the high dielectric constant of ceramic particles with the high dielectric breakdown strength of a polymer. Self-assembled monolayers of electron rich or electron poor organophosphate coupling groups were applied to affect the filler-polymer interface and investigate the role of this interface on composite behavior. The interface has potential to influence dielectric properties, in particular the leakage and breakdown resistance. The composite films synthesized from the modified filler particles dispersed into an epoxy polymer matrix were analyzed by dielectric spectroscopy, breakdown strength, and leakage current measurements. The data indicate that significant reduction in leakage currents and dielectric losses and improvement in dielectric breakdown strengths resulted when electropositive phenyl, electron-withdrawing functional groups were located at the polymer-particle interface. At a 30 vol % particle concentration, dielectric composite films yielded a maximum energy density of ~8 JĘcm(-3) for TiO2-epoxy nanocomposites and ~9.5 JĘcm(-3) for BaTiO3-epoxy nanocomposites. PMID:23452250
Siddabattuni, Sasidhar; Schuman, Thomas P; Dogan, Fatih
Synthesis, characterization and dielectric properties of SnO2 thin films.
SnO2 thin films have been grown on glass substrates using Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature and ambient pressure. The annealing temperature effect on the structural, morphological, optical and electrical properties of SnO2 thin films has been investigated. The X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) studies have showed that all the films have exhibited polycrystalline nature with tetragonal structure and have been covered well on glass substrates. The crystalline and surface properties of the films have improved with increasing annealing temperature. The band gap values have been changed from 3.73 to 3.66eV depending on the annealing temperature. The refractive index (n), optical static and high frequency dielectric constants (?o, ??) values have been calculated as a function of the annealing temperature. The resistivity values of the films have changed between 10(-1) - 10(-3)?cm with annealing temperature and light at room temperature. PMID:24929316
Y?ld?r?m, M Ali; Y?ld?r?m, S³meyra Tuna; Sakar, Emine Fedakar; Ate?, Aytunń
NASA Astrophysics Data System (ADS)
Contamination of soils with non-aqueous phase liquids (NAPLs) is frequently produced by accidental spills and storage tanks or pipes leakage. The main goals dealing with soil and groundwater contamination include determining the extension of the affected zone, monitoring the contaminant plume and quantifying the pollution degree. The objective of this work is to evaluate the potential of dielectric permittivity measurements to detect the presence of NAPLs in sands. Tested samples were fine, medium, coarse and silty sand with different volumetric contents of water and paraffin oil. The dielectric permittivity was measured by means of a Coaxial Impedance Dielectric Reflectometry method in specimens with either known fluid content or at different stages during immiscible displacement tests. A simplified method was developed to quantify the amount of oil from dielectric permittivity measurements and effective mixture media models. Obtained results showed that groundwater contamination with NAPL and the monitoring of immiscible fluid displacement in saturated porous media can be clearly identified from dielectric measurements. Finally, very accurate results can be obtained when computing the contamination degree with the proposed method in comparison with the real volumetric content of NAPL (r2 > 90%).
Francisca, Franco M.; Montoro, Marcos A.
Dielectric properties of betaine phosphite and deuterated betaine phosphite films
Polycrystalline films of betaine phosphite (BPI) and deuterated BPI have been grown by evaporation on LiNbO{sub 3}, {alpha}-SiO{sub 2}, {alpha}-Al{sub 2}O{sub 3}, and NdGaO{sub 3} substrates. These films consist of large single-crystal blocks in which the polar axis (b) lies in the substrate plane. The results of studying the dielectric properties of the films using interdigital electrodes, X-ray diffraction, and block images in a polarized-light microscope in reflection are reported. The film transition into the ferroelectric state at T = T{sub c} is accompanied by strong anomalies of the capacitance of the film/interdigital structure/substrate structure. The deuteration of BPI films leads to an increase in their temperature T{sub c}: from T{sub c} = 200 K for BPI-based structures to T{sub c} = 280 K for structures with a high degree of deuteration (d {approx} 90%).
Balashova, E. V., E-mail: email@example.com; Krichevtsov, B. B.; Zaitseva, N. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Pankova, G. A. [Russian Academy of Sciences, Institute of Macromolecular Compounds (Russian Federation); Frederiks, I. D.; Lemanov, V. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)
Dielectric and electromechanical properties of barium and zirconium co-doped sodium bismuth titanate
Compositional exploration was conducted within the alkaline bismuth titanate system by doping on the A- and B- sites with Ba?▓ and Zr??, respectively. Results on the phase, dielectric and electromechanical properties of ...
Sheets, Sossity A. (Sossity Amber), 1973-
Enhanced dielectric properties from barium strontium titanate films with strontium titanate buffer in their PE state. One of the leading material candidates for tunable materials is barium strontium titanate
Alpay, S. Pamir
Changes in the dielectric properties of rat tissue as a function of age at microwave frequencies
NASA Astrophysics Data System (ADS)
The dielectric properties of ten rat tissues at six different ages were measured at 37 ░C in the frequency range of 130 MHz to 10 GHz using an open-ended coaxial probe and a computer controlled network analyser. The results show a general decrease of the dielectric properties with age. The trend is more apparent for brain, skull and skin tissues and less noticeable for abdominal tissues. The variation in the dielectric properties with age is due to the changes in the water content and the organic composition of tissues. The percentage decrease in the dielectric properties of certain tissues in the 30 to 70 day old rats at cellular phone frequencies have been tabulated. These data provide an important input in the provision of rigorous dosimetry in lifetime-exposure animal experiments. The results provide some insight into possible differences in the assessment of exposure for children and adults.
Peyman, A.; Rezazadeh, A. A.; Gabriel, C.
In this work, we hypothesized that the difference in the dielectric constant value existing between two non-miscible phases such as oil and water could be partially responsible for both protein unfolding and reorganization of the protein structure at the interface. So, we replaced the oil phase, whose dielectric constant value is 2, by organic solvents chosen for both their non-miscibility
E. Cases; P. Cayot
Dielectric Properties of Two-Phase Mixture Ceramics Composed of Rutile and Its Compounds
Dielectric properties of two-phase mixture systems including rutile (TiO2) have been investigated. One of its binary compounds---MnTiO3, ZnTiO3, PbTiO3 and Al2TiO5-was chosen as the second component. Dielectric constants \\\\varepsilonr and their temperature coefficients tau\\\\varepsilon were first examined at 1 MHz. Dielectric properties in the microwave frequency region were measured in the TE011 mode of a cylindrical specimen. The temperature coefficient
Kiyoshi Haga; Tsuyoshi Ishii; Jin-ichi Mashiyama; Takuro Ikeda
PRELIMINARY NON-DESTRUCTIVE ASSESSMENT OF MOISTURE CONTENT, HYDRATION AND DIELECTRIC PROPERTIES OF PORTLAND CEMENT CONCRETE A Thesis by IVAN AVELAR LEZAMA Submitted to the Office of Graduate Studies of Texas A... AND DIELECTRIC PROPERTIES OF PORTLAND CEMENT CONCRETE A Thesis by IVAN AVELAR LEZAMA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE...
Avelar Lezama, Ivan
Dielectric properties and electronic transitions of porous and nanostructured cerium oxide films
Cerium dioxide (CeO2) exhibits exceptional electronic properties such as optical transparency and high refractive index (n) and high dc dielectric constant (k). Therefore, it is an attractive material for ultra-thin gate oxide in CMOS technology, where high-k dielectrics are required. We study the electronic properties of nanostructured and porous cerium oxide (CeOx) films, 110¢500nm thick, grown on Si by electron
S Logothetidis; P Patsalas; E. K Evangelou; N Konofaos; I Tsiaoussis; N Frangis
NASA Astrophysics Data System (ADS)
Phase field modeling and computer simulation is employed to study the relations between filler microstructures and effective properties of dielectric composites. The model solves electrostatic equations in terms of polarization vector field in reciprocal space using a fast Fourier transform technique and parallel computing algorithm. Composites composed of linear constituent phases of different dielectric constants are considered. Interphase boundary conditions are automatically taken into account without explicitly tracking interphase interfaces in the composites. Various factors associated with filler microstructures are systematically investigated, including dielectric constant mismatch between fillers and matrix, particle size, shape, orientation, volume fraction, and spatial arrangement as well as directional alignment. Heterogeneous distributions of polarization, charge density, and local electric field are calculated for each composite microstructure, based on which effective dielectric constant and dielectric anisotropy of the composites are determined. It is found that electrostatic interactions among high-dielectric-constant fillers embedded in low-dielectric-constant matrix play critical roles in determining the composite properties, which sensitively depend on filler arrangement and, especially, directional alignment into fibrous microstructures (chains). Such microstructurally engineered composites, whose fillers are not randomly dispersed, exhibit strong dielectric anisotropy despite all constituent components being isotropic.
Wang, Yu U.; Tan, Daniel Q.
Static properties of hydrostatic thrust gas bearings with curved surfaces.
NASA Technical Reports Server (NTRS)
The classical treatment of circular, hydrostatic, orifice-regulated thrust gas bearings, in which perfectly plane bearing plates are assumed, is extended to include axisymmetric, but otherwise arbitrary, plate profiles. Plate curvature has a strong influence on bearing load capability, static stiffness, tilting stiffness, and side force per unit misalignment angle. By a suitable combination of gas inlet impedance and concave plate profile, the static stiffness can be made almost constant over a wide load range, and to remain positive at the closure load. Extensive measurements performed with convex and concave plates agree with theory to within the experimental error throughout and demonstrate the practical feasibility of using curved plates.
Rehsteiner, F. H.; Cannon, R. H., Jr.
Structural and Dielectric properties of Acid Activated Metakaolinite and Kaolinite
NASA Astrophysics Data System (ADS)
CC31 kaolinite has been metakaolinized and activated with H_2SO_4 of varying concentrations. The samples were characterized using XRD,SEM, and Raman spectroscopy. The dielectric permittivity of these samples were studied.
Izci, E.
Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain
NASA Astrophysics Data System (ADS)
Five sample mixtures of kaolin, ball clay, feldspar and Quartz were formulated and porcelain samples fabricated. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. A composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded a body with high dielectric strength of 19kV/mm compare to an ISO graded product having dielectric strength 14.6 KV/mm after firing at 1225░C.
Tak, S. K.; Shekhawat, M. S.; Mangal, R.
Pyroelectric and dielectric properties of modified lead titanate ceramics
The temperature dependence of pyroelectric coefficient P, relative dielectric constant ?r and dielectric losses tan ? of modified lead titanate ceramics (Pb, Ca) [(Co1\\/2W1\\/2)Ti]O3 with addition of NiO and MnO2 was investigated in the 80¢345 K temperature range. Frequency dependence of ?r and tan ? in low frequency range was studied too. Pyroelectric coefficient P at 80 K is approximately
M. M. Nadoliisky; T. K. Vassileva; R. V. Yanchev
Electrical conductivity and dielectric properties of sulfamic acid doped polyaniline
The temperature and frequency dependence of dielectric constant (??) and dielectric loss (??) is studied for different samples of polyaniline (PANI), doped with different concentration of sulfamic acid in the frequency range (10¢100kHz) and temperature range (300¢400K). The dc conductivity has also been measured to see the effect of sulfamic acid and the conduction mechanism has been explained by the
Sadia Ameen; Vazid Ali; M. Zulfequar; M. Mazharul Haq; M. Husain
Infrared dielectric properties of low-stress silicon nitride.
Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented. PMID:23073410
Cataldo, Giuseppe; Beall, James A; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D; Wollack, Edward J
Dielectric properties of muscle and liver from 500ĀMHz-40ĀGHz.
Dielectric properties are the most important parameters determining energy deposition when biological tissues are exposed to radio frequency and microwave fields. Energy absorption is determined by the specific absorption rate (SAR). SAR distributions can be computed accurately only if the complex relative permittivity of the target tissue is known to a sufficiently high accuracy, and currently there is a lack of data on the dielectric properties of biological tissues at high frequencies. In this study, tissue dielectric properties are measured using an open-ended coaxial probe technique from 500ĀMHz up to 40ĀGHz. We present dielectric data for ex vivo bovine and porcine muscle and liver tissues at 37Ā░C. One-pole Cole-Cole model is used to fit the measured data as a function of frequency and the dispersion parameters are presented. This data is supported by an accurate study on reference liquids such as methanol and ethanediol. PMID:23675628
Abdilla, Lourdes; Sammut, Charles; Mangion, Louis Zammit
SPE 109547 Experimental Validation of Pore-Level Calculations of Static and Dynamic Petrophysical. To test and validate our pore-scale model, we consider three micro-CT images of quartzose sandstones fun- damental macroscopic static and dynamic properties of porous media, including absolute
Torres-Verd├Łn, Carlos
Synthesis and dielectric properties of substituted lanthanum aluminate
LaAlO[sub 3] was chemically modified in order to ascertain the effects of substitution of larger cations on the compound's slight rhombohedral distortion from cubic symmetry--a property that often degrades the performance of LaAlO[sub 3] substrates for epitaxial high-temperature superconducting films. La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Ti[sub x]O[sub 3] (x = 0.05, 0.10, 0.15, 0.25), La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Zr[sub x]O[sub 3], La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Mg[sub x]O[sub 3[minus]2x]F[sub 2x] and La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Sc[sub x]O[sub 3[minus]x]F[sub x] (x = 0.05, 0.10, 0.15) were prepared in polycrystalline form and 1--2 mm single crystals of the Sr, Ti- and Sr,Zr-substituted systems were grown using a PbO-PbF[sub 2]-B[sub 2]O[sub 3]-PbO[sub 2] flux. Shifts in the peak positions of the X-ray powder diffraction patterns confirmed substitution of the larger cations. The diffraction patterns were also typified by line-broadening and a decrease in the rhombohedral splitting at all doping levels. The dielectric constant of LaAlO[sub 3] was unchanged for all of the fluoride-containing systems and for the 5% Sr,Ti- and Sr,Zr-systems.
Vanderah, T.A.; Lowe-Ma, C.K.; Gagnon, D.R. (Naval Air Warfare Center, China Lake, CA (United States))
NASA Technical Reports Server (NTRS)
Data were collected for dominant conifer species. Dielectric properties of trunk wood were measured using a C-band dielectric probe. For certain specimens, electrical resistance was also measured using a shigometer. The water status of the trees studies was determined either by use of a Scholander pressure chamber on branch samples collected simultaneously with dielectric measurements or by fresh-weight/dry-weight assessment of wood core samples extracted and analyzed with the dielectric probe and shigometer. Diurnal delectric properties and xylem water column tension are inversely correlated such that real and imaginary dielectric values drop as tension increases. The dielectric properties were positively correlated with wood core moisture content while electrical resistance was poorly correlated with wood core moisture content in one species studied. Results support the view that dielectric properties are strongly correlated with moisture status in trunk wood, and possibly ion concentrations associated with decay processes in damaged specimens.
Ranson, K. J.; Rock, B. N.; Salas, W. A.; Smith, K.; Williams, D. L.
Structural behavior of alcohol-1,4-dioxane mixtures through dielectric properties using TDR.
The values of complex permittivity for alcohol-1,4-dioxane (DX) mixtures with various concentrations have been determined in the frequency range 10 MHz to 20 GHz using the time domain reflectometry (TDR) method. Numbers of hydrogen bonds between alcohol-alcohol and alcohol-dioxane pairs are estimated from the values of the static dielectric constant by using the Luzar model. The model provides a satisfactory explanation of the experimental results related to the static dielectric constant. The binding energies for alcohol-alcohol (pair 11) and alcohol-DX (pair 12) are estimated to be -13.98 and -16.25 kJ/mol, respectively. The results have also been compared with previous results of the ethyleneglycol-DX system. PMID:19715297
Kumbharkhane, Ashok C; Shinde, M N; Mehrotra, Suresh C; Oshiki, Noriaki; Shinyashiki, Naoki; Yagihara, Shin; Sudo, Seiichi
Optical and dielectric properties of L-methionine L-methioninium hydrogen maleate single crystal
NASA Astrophysics Data System (ADS)
An organic nonlinear optical single crystal L-methionine L-methioninium hydrogen maleate has been grown by solution growth technique. It is confirmed from XRD data that the crystal belongs to monoclinic system with non-centrosymmetric space group P21. Photoluminescence study was carried out for the grown crystal and maximum emission occurs at 395 nm. Dielectric measurements were made for the frequency range from 100 Hz to 5 MHz. The lower value of dielectric constant and dielectric loss at higher frequencies reveal that the material possesses enhanced optical quality with lesser defects. Nonlinear optical property was confirmed by Kurtz and Perry technique.
Vasudevan, P.; Sankar, S.; Gokulraj, S.
A possible coupling mechanism between magnetism and dielectric properties in EuTiO3
NASA Astrophysics Data System (ADS)
The dielectric constant of an incipient ferroelectric EuTiO3 exhibits a sharp decrease at about 5.5K, at which the antiferromagnetic ordering of the Eu spins simultaneously appears. This fact indicates the existence of a coupling between the magnetism and dielectric properties of EuTiO3. We propose a possible coupling mechanism between the magnetic and electrical subsystems as -gsumlsumlanglei,jrangleq2lvec SiĘvec Sj. In the framework of soft-mode theory, we have obtained analytically a dielectric constant expression related to the spin correlation of nearest neighbours of Eu ions.
Jiang, Qing; Wu, Hua
Dielectric Properties of Two-Phase Mixture Ceramics Composed of Rutile and Its Compounds
NASA Astrophysics Data System (ADS)
Dielectric properties of two-phase mixture systems including rutile (TiO2) have been investigated. One of its binary compoundsŚMnTiO3, ZnTiO3, PbTiO3 and Al2TiO5-was chosen as the second component. Dielectric constants \\varepsilonr and their temperature coefficients ?\\varepsilon were first examined at 1 MHz. Dielectric properties in the microwave frequency region were measured in the TE011 mode of a cylindrical specimen. The temperature coefficient of resonant frequency, ?f, of MnTiO3 was negative, and a zero coefficient was found at an intermediate composition x{=}0.13 in the (1-x) MnTiO3-xTiO2 system. In the PbTiO3-TiO2 system, zero ?\\varepsilon composition was confirmed at low frequencies, but composition modification trials aiming to make microwave dielectric measurements possible were unsuccessful throughout the entire system.
Haga, Kiyoshi; Ishii, Tsuyoshi; Mashiyama, Jin-ichi; Ikeda, Takuro
Dielectric properties of rat embryo and foetus as a function of gestation
NASA Astrophysics Data System (ADS)
The dielectric properties of rat embryos/foetuses have been acquired at several stages of gestation at 37 ░C and in the frequency range of 40 MHz-20 GHz. Measurements were carried out on homogenized tissues, as trial experiments did not show any systematic difference between the dielectric data of intact and homogenized tissues at microwave frequencies. The results showed that dielectric properties of the foetus are generally higher than adult muscle and brain. The measured data also showed some decline for both permittivity and conductivity as the foetus grew from 18 to 20 days old; however, these changes were not statistically significant. Data were also collected for placenta and amniotic fluid which were in good agreement with those recently obtained from human tissues. Finally, tabulated numerical dielectric data for rat foetal tissues are presented for a wide range of medical and telecommunication frequencies.
Peyman, A.; Gabriel, C.
Properties and Applications of Silicon Oxynitride Gate Dielectrics.
NASA Astrophysics Data System (ADS)
Reducing the size of silicon CMOS transistors enables higher speed, lower-power, denser and cheaper circuits, but introduces many challenges in process technology. As the gate oxide thickness is reduced, and as electric fields in the MOSFET increase, there are increased concerns about hot-carrier damage and oxide breakdown. Additionally, thinner SiO2 layers cannot effectively block diffusion of dopants and impurities. Silicon oxynitride dielectrics minimize these difficulties, making them attractive as gate dielectrics for future CMOS processes. Silicon oxynitrides are thermally grown on Si, in N_2O at temperatures ranging from 800-1100^circC, to thicknesses of 3-10 nm. The resulting material is primarily SiO_2, with 10^14-10^15 cm-2 nitrogen atoms incorporated (as measured by nuclear reaction analysis), equivalent to less than a monolayer of pure Si_3N_4. Secondary ion mass spectroscopy profiles indicate that this nitrogen is mainly near the crystalline silicon/dielectric interface, as a result of two competing reactions:(E.C. Carr, K.A. Ellis and R.A. Buhrman, Appl. Phys. Lett., v. 66, n. 12, p. 1492, (1995).) first, a nitrogen-oxygen species diffuses through the film and reacts at the Si interface, growing a silicon oxynitride layer. As the reaction proceeds and the grown layer is pushed up from the interface, a competing reaction removes the nitrogen from the dielectric ``bulk'', leaving behind SiO_2. This small amount of nitrogen incorporated at the dielectric interface has a dramatic effect on electrical reliability. Nitrogen-containing gate dielectrics inhibit generation of electrical defects and charge traps that degrade device performance, and they can more than double the time until breakdown. Such improvements are attributed to reduction of strain at the interface, which allows stronger bonds and fewer defect precursors. Oxynitrides also have the advantage of acting as a diffusion barrier. In MOS structures, boron dopant atoms originating in the polycrystalline silicon gate electrode can easily diffuse through thin gate dielectrics, resulting in threshold voltage shifts and degrading process control. Nitrogen in the dielectric inhibits boron diffusion, although the mechanism is still unclear. By blocking boron, these oxynitrides allow more aggressive scaling of oxide thickness. Collaborators: D. Brasen, L.C. Feldman, M.L. Green, W. Lennard, L. Manchanda, H. Tang, B.E. Weir, H. Tang.
Krisch, K. S.
Antiferroelectric and Dielectric Properties of Tin Chloride Dihydrate Crystal
NASA Astrophysics Data System (ADS)
A two-sublattice pseudospin lattice coupled mode model along with third-and- fourth order phonon anharmonic interaction terms has been considered by using double-time thermal Green's function method for SnCl2.2H2O crystal, expressions for shift, width, renormalized soft mode frequency, Curie temperature, dielectric constant and loss tangent are obtained for tin chloride dehydrate crystal. By fitting model values of physical quantities temperature dependences of soft mode frequency, dielectric constant and loss tangent have been calculated for tin chloride dehydrate crystal. Theoretical results compare well with experimental results of Mognaschi et al [Phys. Rev. B., 14 (1976)2005
Upadhyay, Trilok Chandra; Sati, Pramod
Dielectric properties of barium titanate nanocube ordered assembly sintered at various temperatures
NASA Astrophysics Data System (ADS)
Single-crystalline BaTiO3 nanocubes were synthesized by a hydrothermal method using a water-soluble titanium complex and surfactants. Ordered assemblies of BaTiO3 nanocubes were directly fabricated on substrates by the dip-coating method. To optimize the conjugation of the nanocubes, the sintering temperature was changed in the range of 750 to 900 ░C to compare with the dielectric properties. The microstructures and dielectric properties of BaTiO3 nanocube assemblies sintered at various temperatures were characterized. The structure-property relation and the sintering temperature dependence of the dielectric properties are discussed. The assembly sintered at 850 ░C showed the most enhanced dielectric properties. The face-to-face conjugation of the nanocubes was completed and there was good adhesion between the electrode and the assembly at 850 ░C. The enhanced dielectric properties were considered to be due to the combination of the single-crystalline nanocubes and the interface between them.
Mimura, Ken-ichi; Kato, Kazumi
Dielectric properties of Be(IO 3 ) 2 ?4H 2 O crystals
The article studies the dielectric properties, dc conductivity and ac conductivity of Be(IO3)2?4H2O single crystals. The dielectric constant ? has been defined for the three directions of the vectors a, b and c in the crystals in the temperature interval 280¢340 K and frequency range 100 Hz¢106 Hz. The crystals show strongly expressed anisotropy, at 20 ?C and frequency 100
M. M. Nadoliisky; M. P. Georgiev; D. K. Nikolova; V. A. Karadjova
Non-linear dielectric properties of BiFeO3 ceramics
NASA Astrophysics Data System (ADS)
The nonlinear dielectric properties of BiFeO3 ceramics as a function of temperature were investigated. The present results demonstrate a high dielectric tunability in quite low range of the bias electric fields over a broad temperature interval around the room temperature. The non-linear permittivity-field response results from multiple contributions, whose weights are different at various temperatures and in different field ranges.
Curecheriu, Lavinia; Gheorghiu, Felicia; Ianculescu, Adelina; Mitoseriu, Liliana
Voltage and frequency dependent dielectric properties of BST-0.5 thin films on alumina substrates
Dielectric properties of Ba0.5Sr0.5TiO3 (BST-0.5) polycrystalline thin films, deposited on alumina substrates by means of reactive pulsed laser deposition (PLD), were measured at GHz frequencies using an interdigital capacitor (IDC). By applying a voltage up to 40 V between the two groups of fingers at room temperature, a high tunability of ?27% was achieved at 5 GHz. A relative dielectric
Sķbastien Delprat; Mossaab Ouaddari; Franńois Vidal; Mohamed Chaker; Ke Wu
Effect of Uniaxial Stress on Dielectric Properties of 0¢3 PZT-Portland Cement Composite
The effects of uniaxial stress on the 0¢3 lead zirconate titanate (PZT)-portland cement (PC) composite were investigated. PZT and PC composites were fabricated using 50% of PZT by volume. At room temperature, the dielectric properties were measured under stress free and stress level up to 57 MPa at the frequency of 1¢100 kHz. The results showed that the dielectric constant
N. Jaitanong; R. Yimnirun; A. Chaipanich
Dielectric properties of an ytterbium-based nematic liquid-crystal complex
NASA Astrophysics Data System (ADS)
The dielectric properties of an yttrium-based paramagnetic thermotropic nematic liquid-crystal complex have been studied. The conditions for the measurement of the magnitude and sign of the dielectric anisotropy of the mesophase have been determined. The relaxation of the components of the relative permittivity of a macroscopically homogeneously oriented sample has been observed. A high polarity of the metallomesogenic complex has been revealed.
Dobrun, L. A.; Sakhatskii, A. S.; Kovshik, A. P.; Ryumtsev, E. I.; Knyazev, A. A.; Galyametdinov, Yu. G.
The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s-1 at heights of 1-2 mm are reached when filamentary discharges with current peaks up
Jķr¶me Pons; Eric Moreau; Gķrard Touchard
Dielectric properties of the BaTiO 3 -AlN-additive system
The mixed system of BaTiO3 and AlN has been investigated in terms of dielectric properties and microstructure. Two different types of additives, bismuth\\u000a oxide and bismuth borosilicate glass, were used to lower sintering temperature. First, the addition of a fixed content (3\\u000a wt.%) of Bi2O3 provided densification at 1200?C where monotonous decreases of dielectric constant were found with increasing the
Yong Soo Cho; Dong Joo Shin; In June Kim; Hyung Sub Lee; Dong Suck Jeong
A possible coupling mechanism between magnetism and dielectric properties in EuTiO3
The dielectric constant of an incipient ferroelectric EuTiO3 exhibits a sharp decrease at about 5.5K, at which the antiferromagnetic ordering of the Eu spins simultaneously appears. This fact indicates the existence of a coupling between the magnetism and dielectric properties of EuTiO3. We propose a possible coupling mechanism between the magnetic and electrical subsystems as -gsumlsumlanglei,jrangleq2lvec SiĘvec Sj. In the
Qing Jiang; Hua Wu
Coupling between the magnetism and dielectric properties in Eu1-xBaxTiO3
The dielectric constant of the quantum paraelectric EuTiO3 exhibits a sharp decrease at about 5.5 K, at which temperature antiferromagnetic ordering of the Eu spins simultaneously appears, indicating coupling between the magnetism and dielectric properties. A similar feature has also been detected in Eu1-xBaxTiO3 (0 Hua Wu; Qing Jiang; Wen Zhong Shen 2004-01-01
Acid Rain Affecting the Electrical Properties of Outdoor Composite Dielectric Materials
NASA Astrophysics Data System (ADS)
Acid rain is precipitation with acidity, i.e., pH, below 5.6. There is an increasing interest in the degradation of the electrical properties of outdoor composite dielectric materials under severe contaminant conditions such as acid rain. In this study, the degradation effects of acid rain on the outdoor composite dielectrics are investigated by accelerated aging due to artificial acid rain. Based on the investigation of acid rain, the composition of artificial acid rain is chosen to agree with the actual composition of precipitation. The surface potential, breakdown voltage, tracking resistance, and surface discharge current of dielectric materials are studied. Furthermore, the degradation mechanisms of electrical properties of composite dielectrics are discussed by investigating the degradation of the chemical and physical microstructures of material surface using Fourier transform infrared (FTIR), the X-ray diffraction spectrum (XDS), and the metalloscope. Experimental results show that the outdoor polymeric dielectrics suffer severely and degrade due to acid rain so that their surface electrical properties deteriorate after aging. The erosion, by acid rain, of the energized dielectric materials is larger than that of outdoor materials used for other purposes.
Wang, Xinsheng; Kumagai, Seiji; Yoshimura, Noboru
Dielectric properties of grapes and sugar solutions at 2.45 GHz.
Dielectric properties of grapes at 2.45 GHz were measured at moisture contents varying from 80 to 15% (wet basis) at temperatures ranging from 25-80 degrees C using the Open Ended Coaxial Transmission Line Technique. Both dielectric constant and loss factor decreased with decreasing moisture content. In low moisture samples these properties were found to be considerably influenced by higher temperatures. Dielectric properties of sugar solutions of varying concentrations (20-250% by weight in water) were also determined at different temperatures, and these values were compared to those of grapes of corresponding moisture concentration. Predictive models of the dieletric properties as functions of moisture content and temperature were generated using response surface methodology. The results are useful in estimating the volumetric heating of grapes by microwave energy, and these methods can be extended to sugar-based foods in general. PMID:7643292
Tulasidas, T N; Raghavan, G S; van de Voort, F; Girard, R
The Dielectric Properties of Water and Heavy Water
Measurements by a number of different methods of the dielectric constant and loss angle of water and heavy water at three widely separated wavelengths in the region of anomalous dispersion, ?=10 cm., 3 cm., 1.25 cm., are described. Results show that the Debye equations are exactly obeyed, there being a single time of relaxation varying with the temperature; the ratios
C. H. Collie; J. B. Hasted; D. M. Ritson
Derivation of the cell dielectric properties based on Clausius-Mossotti factor
NASA Astrophysics Data System (ADS)
The dielectric properties of membrane and cytoplasm of cells were commonly derived using the experimental electrorotation spectra, which are proportional to the spectra of the imaginary part of the Clausius-Mossotti factor (Ki). However, it was found in this study that the cell properties thus derived do not agree with those derived using the experimental spectra of the real part of the Clausius-Mossotti factor (Kr). Both the Kr and Ki spectra are required simultaneously for deriving appropriate cell dielectric properties. Also the membrane and cytoplasm conductivities decrease, while the membrane and cytoplasm permittivities remain relatively unchanged, as the medium conductivity decreases.
Lo, Y. J.; Lei, U.; Chen, K. Y.; Lin, Y. Y.; Huang, C. C.; Wu, M. S.; Yang, P. C.
The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number
Mariya Lazebnik; Leah McCartney; Dijana Popovic; Cynthia B. Watkins; Mary J. Lindstrom; Josephine Harter; Sarah Sewall; Anthony Magliocco; John H. Booske; Michal Okoniewski; Susan C. Hagness
An analysis of local and global mechanisms of heat generation and distribution in carbon-fiber-based composites subjected to an alternating magnetic field has shown that heating is dependent upon the dielectric properties of the polymer matrix. These properties were investigated ...
Dielectric properties of a novel high absorbing onion-like-carbon based polymer composite
Dielectric properties of a novel high absorbing onion-like-carbon based polymer composite J resonance devices, for targeting radars and vehicle speed detection, for intelligent transportation systems properties and unique electronic structure [12], being incorporated into the polymer matrix, demonstrate
Mayer, Alexandre
Improving the Dielectric Properties of Ethylene-Glycol Alkanethiol Self-Assembled Monolayers
Self-assembled monolayers (SAMs) can be formed at the interface between solids and fluids, and are often used to modify the surface properties of the solid. One of the most widely employed SAM systems is exploiting thiol-gold chemistry, which, together with alkane-chain-based molecules, provides a reliable way of SAM formation to modify the surface properties of electrodes. Oligo ethylene-glycol (OEG) terminated alkanethiol monolayers have shown excellent antifouling properties and have been used extensively for the coating of biosensor electrodes to minimize nonspecific binding. Here, we report the investigation of the dielectric properties of COOH-capped OEG monolayers and demonstrate a strategy to improve the dielectric properties significantly by mixing the OEG SAM with small concentrations of 11-mercaptoundecanol (MUD). The monolayer properties and composition were characterized by means of impedance spectroscopy, water contact angle, ellipsometry and X-ray photoelectron spectroscopy. An equivalent circuit model is proposed to interpret the EIS data and to determine the conductivity of the monolayer. We find that for increasing MUD concentrations up to about 5% the resistivity of the SAM steadily increases, which together with a considerable decrease of the phase of the impedance, demonstrates significantly improved dielectric properties of the monolayer. Such monolayers will find widespread use in applications which depend critically on good dielectric properties such as capacitive biosensor. PMID:24447311
Effect of surface modification on the dielectric properties of BaTiO3 nanocrystals.
We present the first direct comparison of the dielectric properties of organically modified BaTiO(3) nanocrystals with unmodified BaTiO(3) nanocrystals. Well-defined 6 nm BaTiO(3) nanocrystals were functionalized with n-hexylphosphonic acid (HPA) to give a surface coverage of 2.4 phosphonate groups/nm(2). Chemisorption of HPA to the oxide surface occurs mainly via tridentate bonding of the deprotonated phosphonate, as determined by (31)P MAS NMR, FT-IR, and XPS spectroscopies. The HPA-modified BaTiO(3) (HPA-BaTiO(3)) nanocrystals possess improved dielectric properties, as demonstrated by decreased sensitivity to temperature and frequency for both the dielectric constant and dielectric loss. HPA-BaTiO(3) had a much lower dielectric loss than unmodified BaTiO(3), which also indicates an improvement in the dielectric quality of the material. Such improvements are of potential importance for the fabrication of high energy density nanocomposites. PMID:20039602
Beier, Christopher W; Cuevas, Marie A; Brutchey, Richard L
We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated)-reinforced high-density polyethylene (HDPE) composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials.
Comparison effects and dielectric properties of different dose methylene-blue-doped hydrogels.
The dielectric properties of methylene blue (MB)-doped hydrogels were investigated by impedance spectroscopy. The real part (?') and the imaginary part (?") of the complex dielectric constant and the energy loss tangent/dissipation factor (tan ?) were measured in the frequency range of 10 Hz to 100 MHz at room temperature for pH 5.5 value. Frequency variations of the resistance, the reactance, and the impedance of the samples have also been investigated. The dielectric permittivity of the MB-doped hydrogels is sensitive to ionic conduction and electrode polarization in low frequency. Furthermore, the dielectric behavior in high-frequency parts was attributed to the Brownian motion of the hydrogen bonds. The ionic conduction for MB-doped samples was prevented for Cole-Cole plots, while the Cole-Cole plots for pure sample show equivalent electrical circuit. The alternative current (ac) conductivity increases with the increasing MB concentration and the frequency. PMID:23799863
Yalń?n, O; Co?kun, R; Okutan, M; ųzt³rk, M
NASA Astrophysics Data System (ADS)
By using the finite element method within the effective mass approximation, the effects of both dielectric confinement and electric field on the shallow-donor binding energy and polarizability in spherical Si quantum dots are investigated. It is found that: (i) the ground state binding energy is significantly increased by the dielectric mismatch at the dot interface, (ii) in the freestanding nanodot the competition between the electric field, polarization charges induced at interfaces and impurity position determines the symmetry of the electron probability distribution; (iii) the donor polarizability decreases with electric field strength and this effect is more pronounced for large dielectric mismatches. Therefore, the electronic properties of the nanocrystals could be tuned by proper tailoring of the surrounding medium dielectric constant as well as by varying the electric field. The normalized binding energy of an on-center hydrogenic donor is also been estimated and the results are in good agreement with the previous reported values.
Niculescu, E. C.; Cristea, M.
Epitaxial growth and in-plane dielectric properties of orthorhombic HoMnO3 films
NASA Astrophysics Data System (ADS)
Orthorhombic HoMnO3 (HMO) thin films were grown epitaxially on LaAlO3 (001) substrates by using pulsed laser deposition technique. The films showed perfect orthorhombic crystallization and were well-aligned with the substrates. The in-plane dielectric constant and loss of HMO films were measured as functions of temperature (80-300 K) and frequency (120 Hz-100 kHz) by using coplanar interdigital electrodes. Two thermally activated dielectric relaxations were found, and the respective peaks shifted to higher temperatures as the measuring frequency increased. The in-plane dielectric properties of epitaxial orthorhombic HMO films were considered as universal dielectric response behavior, and the dipolar effects and the hopping conductivity induced by the charge carriers were used to explain the results.
Gao, Ping; Wang, WeiTian; Zhang, Wei; Sun, YuMing
Epitaxial growth and in-plane dielectric properties of orthorhombic HoMnO3 films
NASA Astrophysics Data System (ADS)
Orthorhombic HoMnO3 (HMO) thin films were grown epitaxially on LaAlO3 (001) substrates by using pulsed laser deposition technique. The films showed perfect orthorhombic crystallization and were well-aligned with the substrates. The in-plane dielectric constant and loss of HMO films were measured as functions of temperature (80-300 K) and frequency (120 Hz-100 kHz) by using coplanar interdigital electrodes. Two thermally activated dielectric relaxations were found, and the respective peaks shifted to higher temperatures as the measuring frequency increased. The in-plane dielectric properties of epitaxial orthorhombic HMO films were considered as universal dielectric response behavior, and the dipolar effects and the hopping conductivity induced by the charge carriers were used to explain the results.
Gao, Ping; Wang, WeiTian; Zhang, Wei; Sun, YuMing
NASA Astrophysics Data System (ADS)
We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated)-reinforced high-density polyethylene (HDPE) composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials.
Liu, Tian; Wood, Weston; Zhong, Wei-Hong
In-Vivo Time Domain Measurement of Dielectric Properties of Human Body Tissue
NASA Astrophysics Data System (ADS)
It is essential to measure dielectric properties of human tissues for the safety evaluation of electromagnetic field exposures. In this paper, towards developing an in-vivo measurement method for living human tissues, we employed an open-ended coaxial probe together with a time domain reflectometry (TDR) technique, which probably enables us to extract a reflected waveform from some specified tissues in the time domain. We compared the TDR-measured dielectric properties for human surface tissues with those derived from a conventional frequency-domain technique. As a result, we found a fair agreement between them in the frequency range from 300 MHz to 6 GHz. This result suggests the possibility of in-vivo dielectric property measurement for superficial human tissues by using the proposed TDR technique.
Koyama, Kazunori; Hirata, Akimasa; Wang, Jianquing; Fujiwara, Osamu
Tailoring the Microwave Dielectric Properties of Alkaline Earth Gehlenite Type Ceramic
NASA Astrophysics Data System (ADS)
The effect of glass fluxing and isovalent substitution on the microwave dielectric properties of low permittivity Sr2Al2SiO7 (SAS) ceramic has been investigated. X - ray diffraction pattern of all the compositions indicate the formation of tetragonal Gehlenite type ceramics with space group P/line{4}21m (no. 113). The addition of small amounts of lithium magnesium zinc borosilicate (LMZBS) glass to Sr2Al2SiO7 ceramic enhanced the densification. Glass fluxing also improved the quality factor and relative permittivity. A small partial substitution of Al3+ and Si4+ by Ga3+ and Ge4+ was found to degrade the dielectric properties of SAS ceramic. The composition Sr2Al2SiO7 + 1 wt. % LMZBS glass showed the best dielectric properties with ?r = 7.3, Quūf = 36000 GHz and ?f = -23.0 ppm/░C.
Arun, B.; Manu, K. M.; Sebastian, M. T.
Dielectric properties of wheat flour mixed with oat meal
NASA Astrophysics Data System (ADS)
Possibilities of using electric methods for determining admixtures of oat meal to wheat flour, type 650 are presented. In wheat flour, oat meal and mixtures containing 10, 20 and 30% of the oat meal, moisture, protein, starch and ash content, sedimentation value, yield and softening of wet gluten were determined. In samples containing 0, 5, 10, 15, 20, 25, 30 and 100% of oat meal, the dielectric loss factor and conductivity were determined using an impedance analyzer for electromagnetic field frequency ranging from 0.1-20 kHz. It was found that the dielectric loss factor varied for tested material. The best distinguishing between tested mixtures was obtained at the measuring electromagnetic field frequency of 20 kHz. The loss factor was significantly correlated with the yield of wet gluten and the sedimentation value, parameters indicating the amount and quality of gluten proteins in flour.
?uczycka, D.; Czubaszek, A.; Fujarczuk, M.; Pruski, K.
Ferroelectric films of deuterated glycine phosphite: Structure and dielectric properties
NASA Astrophysics Data System (ADS)
Polycrystalline textured films of deuterated glycine phosphite consisting of single-crystal blocks with lateral dimensions ś(50-100) ?m and a thickness d ś (1-5) ?m have been grown by evaporation on NdGaO3(100) and ?-Al2O3 substrates with preliminarily deposited interdigitated electrodes, as well as on Al substrates. The c* ( Z) crystallographic axis in the blocks is normal to the film plane, and the a ( X) axis and the polar axis b ( Y) are oriented in the film plane. The temperature dependences of the capacitance of the structures measured with the interdigitated electrode system reveal a strong dielectric anomaly at the film transition to the ferroelectric state. The phase transition temperature T c depends on the degree of deuteration D of the glycine phosphite. The maximum value T c = 275 K obtained in the structures studied corresponds to a degree of deuteration of the glycine phosphite D ś 50%. The frequency behavior of the dielectric hysteresis loops in glycine phosphite films differs radically from that of the previously studied films of deuterated betaine phosphite, which evidences that polarization switching in these structures proceeds by different mechanisms. It has been that application of a dc bias to the electrodes changes the shape of the dielectric hysteresis loops and shifts them along the electric field axis. The shift of the loops depends on the sign, magnitude, and time of application of the bias. Possible mechanisms underlying the induced unipolarity are discussed.
Balashova, E. V.; Krichevtsov, B. B.; Svinarev, F. B.; Lemanov, V. V.
Nano-structured vanadium: processing and mechanical properties under quasi-static and dynamic form 16 September 2003; accepted 9 October 2003 Abstract We have processed fully dense, nano that the grain size of the consolidated V is around 100 nm. Mechanical properties of the nano-structured V were
Wei, Qiuming
This work describes and evaluates a technique for determining the dielectric properties of carbon-black filled Ethylene Vinyl Acetate (EVA) rubber and presents results on the studies of the effect of frequency on the permittivity and microwave conductivity using resonant cavity perturbation method. The measurements are performed with the aid of a Network Analyzer in X-band. The simplicity of this method lies in the fact that the dielectric properties can be obtained directly from the analytical formula without taking recourse to calibration. PMID:24427870
Banerjee, Prasun; Biswas, Salil Kumar; Ghosh, Gautam
The rising popularity of microwaves for drying, material processing and quality sensing has fuelled the need for knowledge concerning dielectric properties of common pharmaceutical materials. This article represents one of the few reports on the density and moisture content dependence of the dielectric properties of primary pharmaceutical materials and their relevance to microwave-assisted processing. Dielectric constants (epsilon') and losses (epsilon'') of 13 pharmaceutical materials were measured over a frequency range of 1 MHz-1 GHz at 23 +/- 1 degrees C using a parallel-electrode measurement system. Effects of field frequency, material density and moisture content on dielectric properties were studied. Material dielectric properties varied considerably with frequency. At microwave frequencies, linear relationships were established between cube-root functions of the dielectric parameters [symbols: see text] and density which enabled dielectric properties of materials at various densities to be estimated by regression. Moisture content was the main factor that contributed to the disparities in dielectric properties and heating capabilities of the materials in a laboratory microwave oven. The effectiveness of a single frequency density-independent dielectric function for moisture sensing applications was explored and found to be suitable within low ranges of moisture contents for a model material. PMID:19708060
Heng, Paul W S; Loh, Z H; Liew, Celine V; Lee, C C
Spin Waves and Dielectric Softening of Polar Molecule Condensates
NASA Astrophysics Data System (ADS)
We consider an oblate Bose-Einstein condensate of heteronuclear polar molecules in a weak applied electric field. This system supports a rich quasiparticle spectrum that plays a critical role in determining its bulk dielectric properties. In particular, in sufficiently weak fields the system undergoes a polarization wave rotonization, leading to the development of textured electronic structure and a dielectric instability that is characteristic of the onset of a negative static dielectric function.
Wilson, Ryan M.; Peden, Brandon M.; Clark, Charles W.; Rittenhouse, Seth T.
Dielectric properties of tetragonal tungsten bronze films deposited by RF magnetron sputtering
NASA Astrophysics Data System (ADS)
Tetragonal tungsten bronze (TTB) films have been synthesised on Pt(111)/TiO2/SiO2/Si substrates from Ba2LnFeNb4O15 ceramics (LnĀ=ĀLa, Nd, Eu) by RF magnetron sputtering. X-ray diffraction measurements evidenced the multi-oriented nature of films with some degrees of preferential orientation along (111). The dependence of the dielectric properties on temperature and frequency has been investigated. The dielectric properties of the films are similar to those of the bulk, i.e., ? ?150 and ? ?10-6Ā?-1Ācm-1 at 1ĀMHz and room temperature. The films exhibit two dielectric anomalies which are attributed to Maxwell Wagner polarization mechanism and relaxor behaviour. Both anomalies are sensitive to post-annealing under oxygen atmosphere and their activation energies are similar Ea ?0.30ĀeV. They are explained in terms of electrically heterogeneous contributions in the films.
Bodeux, Romain; Michau, Dominique; Josse, Michaļl; Maglione, Mario
Magnetic, dielectric and sensing properties of manganese substituted copper ferrite nanoparticles
NASA Astrophysics Data System (ADS)
Manganese substituted copper ferrite nanoparticles were synthesized by an auto-combustion technique using metal nitrates and urea for gas sensor application. The products were characterized by XRD, SEM, EDX, TEM and VSM techniques. The effect of annealing temperature on the particle size, magnetic and dielectric properties of Mn-Cu ferrite nanoparticles was analyzed. The size of the particles are in the range of ~9-45 nm. The effect of annealing on the magnetic properties is discussed with the help of variation in saturation magnetization (Ms) and coercivity (Hc) by vibrating sample magnetometer (VSM). The dielectric loss and dielectric constant have been measured in the frequency range of 100 kHz-5 MHz. Furthermore, Conductance response of Mn-Cu ferrite nanomaterial was measured by exposing the material to reducing gas like liquefied petroleum gas (LPG).
Kumar, E. Ranjith; Jayaprakash, R.; Devi, G. Sarala; Reddy, P. Siva Prasada
Ferroelectric betaine phosphite films: Growth, optical imaging, and dielectric properties
NASA Astrophysics Data System (ADS)
Polycrystalline films of betaine phosphite (BPI) were grown by evaporation method on SiO2 and LiNbO3 substrates with interdigital transducers. Large (ś1 mm) single-crystalline blocks were visualized in a polarizing microscope in the reflection mode. Temperature dependences of the film capacity at frequencies 120 Hz-1 MHz exhibit a strong maximum at the temperature of the ferroelectric phase transition of BPI bulk crystals. The effect of a bias electric field was studied. Temperature variations in dielectric permittivity and electric field effect are analyzed using a thermodynamic model accounting for the substrate-film interaction.
Balashova, E. V.; Krichevtsov, B. B.; Lemanov, V. V.
Effect of crystal structure on strontium titanate thin films and their dielectric properties
NASA Astrophysics Data System (ADS)
Strontium titanate (SrTiO3 or STO) has application in radio and microwave-frequency tunable capacitor devices particularly at low temperatures due to its high dielectric constant, low loss and the electric field tunability of its dielectric constant. The main goal of improving the performance in these devices is to increase the tunability and decrease the dielectric loss at the same time, especially at microwave frequencies. Thin films of STO however, show dramatic differences compared to the bulk. The dielectric constant of bulk STO increases nonlinearly from 300 at room temperature to 30000 at 4 K and the loss range is 10-3--10 -4. On the other hand. STO thin films, while showing a dielectric constant close to 300 at room temperature, typically reach a maximum between 1000 and 10000 in the 30 K to 100 K range before decreasing, and the high-loss range is 10-2--10-3. We have grown strontium titanate thin films using a pulsed laser deposition technique on substrates selected to have a small lattice mismatch between the film and substrate. Neodymium gallate (NdGaO3 or NGO) and lanthanum aluminate (LaAlO3 or LAO) substrates were good candidates due to only 1--2% mismatching. Film capacitor devices were fabricated with 25 micron gap separation. 1.5 mm total gap length and an overall 1 x 2 mm dimension using standard lithography and gold metal evaporative techniques. Their nonlinear dielectric constant and loss tangent were measured at low frequencies and also at 2 GHz, and from room temperature down to 4 K. The resulting films show significant variations of dielectric properties with position on the substrates with respect to the deposition plume axis. In the presence of DC electric fields up to +/-4 V/mum, STO films show improved dielectric tunability and low loss in regions far from the plume axis. We found that the films grown on NCO have lower dielectric loss than those on LAO due to a closer match of the NCO lattice to that of STO. We investigated the possible causes that make dielectric behavior in STO thin films different from the bulk. We characterized such film structures as lattice parameters, out-of-plane grain size, in-plane grain size, thickness, roughness, strains, and defects using ellipsometry, atomic force microscopy, and a high-resolution X-ray diffractometry. In plane grain size and percentage of defects were found to play a major role on the dielectric performance of the films.
Kampangkeaw, Satreerat
Temperature-dependent property measurements on multi-electroded thin-layer dielectrics
A measurement system was designed and assembled for the automatic collection of electrical data for thin-layer dielectrics as a function of temperature. The dielectrics were deposited on platinized silicon by sol-gel processing, and the dielectric thickness was 0.2--0.4 [mu]m. Many ([gt]25) surface electrodes were formed by sputtering gold through a shadow mark, with a typical electrode size of 210[times]210 [mu]m[sup 2]. The measurement equipment was computer controlled, with three-axis digital stepping motors that could scan multi-electroded capacitors and collect statistically meaningful data. The temperature-dependent properties were measured between [minus]100 and 300 [degree]C as a function of frequency (100 Hz to 1 MHz) and applied field strength (0--50 MV/m). Data are reported for sol-gel-derived BaTiO[sub 3], PbZrO[sub 3], and (Pb,La)(Zr,Ti)O[sub 3] (i.e., PLZT) thin-layer capacitors. Capacitance values were typically 500--1000 pF, and the dielectric constant could be determined within a standard deviation of [plus minus]1.3%. Nanocrystalline BaTiO[sub 3] was found to have a dielectric constant of 210 at room temperature with no ferroelectric properties or dielectric anomalies between [minus]80 and 200 [degree]C. Antiferroelectric PbZrO[sub 3] had characteristic field-forced phase transformation behavior to the ferroelectric state with increasing bias. The field-induced polarization was approximately 300 mC/m[sup 2] and the coercive field was 22--28 MV/m. PLZT 8/65/35 had a dielectric constant of 556[plus minus]7 at 25 [degree]C, 100 KHz, and 50 mV.
Tani, T.; Xu, Z.; Moses, P.; Payne, D.A. (Department of Materials Science and Engineering, Materials Research Laboratory, and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States))
NASA Astrophysics Data System (ADS)
In order to modify material properties, nano Ag (diameter less than 20 nm) was successfully made from Ag colloidal sol and uniformly dispersed into silicone resin modified polyester (SP). The dielectric properties of the composite were studied. Resistivity- temperature characteristic of the composite is some different from that of pure SP. The maximal breakdown voltage of the composite is 112% of that of pure SP and dielectric loss can be 8 times of pure SP at power frequency. Dielectric constants of the composites all increased with various contents of nano Ag. Two types of shallow traps (0.52eV and 0.62eV) with trap densities (1.2 ū 1010/cm3 and 2.0 ū 1011/cm3) are found in the composite, which differs from those of pure SP (0.58eV, 3.1 ū 1010/cm3) significantly. Resistivity of the composite is much greater than that of pure SP under cryogenic temperature (77K), which might be treated as the result of Coulomb Blockade effect. From the view of dielectric physics, the different characteristic between the composite and pure SP was discussed and a new concept of nano metal/dielectric materials composite used for device surface protection was introduced.
Dong, Xiaobing; Yin, Yi; Jiang, Xiuchen
We investigated the roles of wave impedance and refractive index in photonic crystals by means of analytical expressions for edges frequencies of a photonic bandgap (PBG) in a one-dimensional photonic crystal with magnetic and dielectric properties. The analytical expressions were derived when the optical thicknesses of layers are the same. The wave impedance governs the formation of PBG's and the
Chul-Sik Kee; Jae-Eun Kim; Hae Yong Park; H. Lim
Dielectric Properties of Apollo 11 Lunar Samples and Their Comparison with Earth Materials
neering. The data can be used in planning future exploration of the moon. Study of the samples can also extend our knowledge of the physical properties of materials formed in extraterrestrial environments. In this paper, we report values of the dielectric constants and losses, and the conductivities that have been measured on Apollo 11 lunar samples 10020, 10057, and 10046,
D. H. Chung; W. B. Westphal; Gene Simmons
Influence of stoichiometry on the dielectric properties of sputtered strontium titanate thin films
concurrently on 100 SrTiO3 and 111 Pt/ 0001 Al2O3 substrates. Films were deposited on platinized sapphire grown concurrently on 100 SrTiO3 , 0001 Al2O3 , and platinized 0001 Al2O3 sub- states. Films wereInfluence of stoichiometry on the dielectric properties of sputtered strontium titanate thin films
York, Robert A.
NASA Astrophysics Data System (ADS)
In the present work, different concentrations of Sm3+doped strontium lithium bismuth borate glasses (SLBiB) have been prepared by melt quench technique and investigated their optical, structural and dielectric properties. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction and SEM analysis. The spectroscopic properties of these glasses were investigated by recording optical absorption, photoluminescence and decay curve analysis. Judd-Ofelt (J-O) theory has been applied for the f ? f transitions of Sm3+ ions to evaluate J-O intensity parameters, ?? (? = 2, 4 and 6). Using the J-O intensity parameters, radiative properties such as transition probabilities (AR), calculated branching ratios (?) and radiative lifetimes (?) are estimated. From the emission spectra, effective bandwidths (??eff) and stimulated emission cross-sections (?p) have been obtained for observed emission levels. From the emission spectra, a strong reddish-orange emission corresponding to the transition, 4G5/2 ? 6H7/2 was observed. The nature of decay curves of 4G5/2 level for different Sm3+concentrations in SLBiB glass has been analyzed. FTIR spectra were recorded to analyze the functional groups present in the glass matrix. From the dielectric properties, variation of dielectric constant, dielectric loss and ac conductivity of Sm3+ doped different glass samples with the variation of frequency was studied.
Rajesh, D.; Balakrishna, A.; Ratnakaram, Y. C.
We report structural and optical properties of three-dimensional periodic metallic woodpile structures obtained by direct laser writing in dielectric photoresist SU-8 and subsequent electroless coating by a thin Ni film. Signatures of photonic stop gaps were observed in optical reflection spectra of the structures at infrared wavelengths. This study demonstrates that the combination of DLW and chemical infiltration of metals
Vygantas Mizeikis; Saulius Juodkazis; Rima Tarozaite; Jurga Juodkazyte; Kestutis Juodkazis; Hiroaki Misawa
Effect of side chains on the dielectric properties of alkyl esters derived from palm kernel oil
Alkyl ester derivatives were synthesized from laboratory purified palm kernel oil. The steps in the synthesis involved transesterification of palm kernel oil to produce a methyl ester, followed by epoxidation and then the grafting of side chains by esterification with propionic and butyric anhydride. The dielectric and thermal properties of the ester derivatives were analyzed and compared with the methyl
A. A. Abdelmalik; J. C. Fothergill; S. J. Dodd; A. P. Abbott; R. C. Harris
Dielectric properties of porous granular matter, in relation with Rosetta cometary mission.
NASA Astrophysics Data System (ADS)
Dielectric property measurements over a large range of frequencies on two different samples of granular matter (JSC-MARS1 martian soil simulant and Etna pyroclastic deposits, each them divided at least in three size distribution) are presented. They are under development to prepare the interpretation of Rosetta spacecraft observations of the subsurface and interior of the comet nucleus.
Brouet, Y.; Levasseur-Regourd, AC.; Encrenaz, P.; Gheudin, M.; Ruffiķ, G.; Bonnaudin, F.; Gulkis, S.; Landry, P.; Munier, J. M.; Ciarletti, V.; Batrung, M.
Magnetic, structural, and dielectric properties of CuB2O4
NASA Astrophysics Data System (ADS)
We have studied the magnetic, structural, and dielectric properties of a single crystal of CuB2O4 . We show that both reported magnetic transitions are observable in the magnetization, irrespective of the measured direction of the crystal. This is in agreement with recent neutron data. More importantly, our study demonstrates the absence of dielectric anomalies at the various magnetic transitions despite the reported magnetoelectric symmetry. This demonstrates that the polarization remains zero at any temperature. Consequently, we interpret our data as the evidence for a very weak or the absence of linear magnetoelectric coupling in this material.
Nķnert, G.; Bezmaternykh, L. N.; Vasiliev, A. N.; Palstra, T. T. M.
Magnetic, structural, and dielectric properties of CuB{sub 2}O{sub 4}
We have studied the magnetic, structural, and dielectric properties of a single crystal of CuB{sub 2}O{sub 4}. We show that both reported magnetic transitions are observable in the magnetization, irrespective of the measured direction of the crystal. This is in agreement with recent neutron data. More importantly, our study demonstrates the absence of dielectric anomalies at the various magnetic transitions despite the reported magnetoelectric symmetry. This demonstrates that the polarization remains zero at any temperature. Consequently, we interpret our data as the evidence for a very weak or the absence of linear magnetoelectric coupling in this material.
Nenert, G.; Palstra, T. T. M. [Solid State Chemistry Laboratory, Zernike Institute for Advanced Materials, University of Groningen, Nijenborg 4, 9747 AG Groningen (Netherlands); Bezmaternykh, L. N. [L. V. Kirensky Institute of Physics, Siberian Branch of RAS, Krasnoyarsk 660036 (Russian Federation); Vasiliev, A. N. [Low Temperature Physics Department, Moscow State University, Moscow 119991 (Russian Federation)
Dielectric properties and conductivity in CuO and MoO 3 doped borophosphate glasses
A novel set of glasses of the type (B2O3)0.10¢(P2O5)0.40¢(CuO)0.50?x¢(MoO3)x, 0.05?x?0.50, have been investigated for dielectric properties in the frequency range 100Hz¢100kHz and temperature range 300¢575K. From the total conductivity derived from the dielectric spectrum the frequency exponent, s, and dc and ac components of the conductivity were determined. The temperature dependence of dc and ac conductivities at different frequencies was
B. Vijaya Kumar; T. Sankarappa; Santosh Kumar; M. Prashant Kumar; P. J. Sadashivaiah; R. Ramakrishna Reddy
The Effect of Alkali Treatment on Dielectric Properties of Roystonea regia\\/Epoxy Composites
The present study investigates the electrical conductivity and dielectric properties of untreated and alkali-treated Roystonea regia natural fiber¢reinforced epoxy composites at different frequencies along with compression and water absorption properties. Fiber was treated with 5% NaOH and characterized by chemical, thermogravimetric, tensile test, and SEM methods before and after alkali treatment. The interface between matrix and fiber was studied by
Govardhan Goud; R. N. Rao
The semiconductor industry is gradually moving from well-established Al\\/SiO2 technology to the new Cu\\/low-k interconnects, which brings a challenge in terms of poor thermal and\\/or mechanical properties of low-K dielectric films. Extensive nanoindentation studies have been undertaken on organo-silicate glass (OSG) low-K films to explore their mechanical and fracture properties. A cube corner indentation method was used to measure the
Alex A. Volinsky; Joseph B. Vella; William W. Gerberich
NASA Astrophysics Data System (ADS)
Fe40Co60 powders were produced by mechanical Alloying (MA) route. Structural and microwave dielectric properties were investigated. Discussion of obtained results is conducted according to milling time. X-Ray powder Diffraction (XRD) shows that disordered ? (Fe40Co60) solid solution of substitution with body centered cubic (bcc) lattice is formed after 2h milling. Halder Wagner analysis reveals that least grain size of 15.59 nm and residual strain up to 0.8% are reached after 60h milling. The evolution of the Voigtian mixing factors according to milling progression confirms that structural properties are governed by residual strain accumulated during high- energy mechanical alloying (Gaussian profiles). Scanning Electron Microscopy (SEM) indicates that obtained powders adopt flattened angular shapes with high surface area. Microwave measurements are undertaken on bulk samples. High values of the dielectric permittivity depicting the conductive behavior of Fe-Co powders are measured. Dielectric permittivity spectra according to milling time shift towards higher values. Enhancement of the dielectric properties is related to the developed structure after milling.
Otmane, F.; Bergheul, S.; Triaa, S.; Azzaz, M.
NASA Astrophysics Data System (ADS)
Dense Ba0.4Sr0.6TiO3-Mg2TiO4 composite ceramics with different grain sizes were prepared by three different sintering methods: spark plasma sintering, two-step sintering, and conventional sintering, respectively. The dielectric response, tunability, and loss properties of composite ceramics as a function of volume fraction of Mg2TiO4 were systematically investigated. The results showed that the dielectric constant and tunability are strongly dependent on the concentration of Mg2TiO4, grain sizes, and composite modes. In particular, near the percolation threshold for Mg2TiO4 volume fraction (ś60 vol. %), a remarkable variation of the tunability was observed. Nevertheless, the dielectric loss exhibited a relatively weak dependence on inclusion concentrations. The results are also in agreement with the theoretical predictions of the modified effective medium approximation approaches in the spherical inclusion model of composites.
Zhang, Qiwei; Zhai, Jiwei; Zhang, Haijun; Yao, Xi
Study to determine dielectric properties of sandstone, shale, coal, and slate
NASA Technical Reports Server (NTRS)
Triplicate dielectric constant and loss tangent measurements on samples of sandstone, shale, coal, and slate were performed. Each of the three necessary configurations of the coal material was sampled to obtain measurements, with each sample machined parallel to the coal layering orientation. The coal samples were machined perpendicular to the coal layering and measured. They were conditioned at 100% humidity and at room temperature and remeasured; then conditioned in an elevated environment, and remeasured for dielectric properties. The coal data appear to remain relatively constant over the microwave frequency region. At the Ghz frequencies, the relative dielectric constant of coal is slightly higher for the E-field parallel to the layers than for the perpendicular case.
Bassett, H. L.; Sheppard, A. P.
AC conductivity and dielectric properties of bulk tungsten trioxide (WO3)
NASA Astrophysics Data System (ADS)
AC conductivity and dielectric properties of tungsten trioxide (WO3) in a pellet form were studied in the frequency range from 42 Hz to 5 MHz with a variation of temperature in the range from 303 K to 463 K. AC conductivity, ?ac(?) was found to be a function of ?s where ? is the angular frequency and s is the frequency exponent. The values of s were found to be less than unity and decrease with increasing temperature, which supports the correlated barrier hopping mechanism (CBH) as the dominant mechanism for the conduction in WO3. The dielectric constant (??) and dielectric loss (??) were measured. The Cole-Cole diagram determined complex impedance for different temperatures.
El-Nahass, M. M.; Ali, H. A. M.; Saadeldin, M.; Zaghllol, M.
Dielectric properties of polymer composites with carbon nanotubes of different diameters.
The dielectric properties of Polymethylmetacrylate (PMMA) composites filled with CVD made multiwalled carbon nanotubes (MWCNT) of different mean outer diameters (d - 9 nm and 12-14 nm) were investigated at temperatures from 300 K to 390 K and in a wide frequency range (20 Hz-1 MHz). The percolation threshold is lower in composites with thick nanotubes. Below percolation threshold the dielectric permittivity was found also to be higher for composites with thicker carbon nanotubes. The temperature dependence of the complex dielectric permittivity of the investigated composites below percolation is mainly caused by beta relaxation in pure PMMA polymer matrix. The potential barrier for PMMA molecules rotation is higher in composites with thicker MWCNT and demonstrates non-monotonous concentration dependence. PMID:24758044
Macutkevic, Jan; Paddubskaya, Alesia; Kuzhir, Polina; Banys, Juras; Maksimenko, Sergey; Kuznetsov, Vladimir L; Mazov, Ilya N; Krasnikov, Dmitrij V
Pyrochlore free lead indium niobate ceramics are successfully prepared using wolframite precursor by conventional solid state reaction method in air atmosphere, by adding an excess amount of MgO in PbO-InNbO{sub 4} mixture. The dielectric properties of lead indium niobate ceramic studied as a function of both temperature and frequency indicate relaxor ferroelectric behavior with maximum dielectric constant of 4310 at 40 {sup {omicron}}C for 1 kHz. Lowering of transition temperature and enhancement of dielectric constant at room temperature, compared to earlier reports, may be due to the diffusion of magnesium ion into the lead indium niobate. The saturation polarization P{sub s}, measured at room temperature, is found to be 22.5 {mu}C/cm{sup 2} for 40 kV/cm.
Ramesh, G. [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India)] [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India); Subramanian, V., E-mail: firstname.lastname@example.com [Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India); Sivasubramanian, V. [Condensed Matter Physics Division, Indira Gandhi Center for Atomic Research, Kalpakkam -603 102 (India)] [Condensed Matter Physics Division, Indira Gandhi Center for Atomic Research, Kalpakkam -603 102 (India)
Coupling between the magnetism and dielectric properties in Eu1-xBaxTiO3
NASA Astrophysics Data System (ADS)
The dielectric constant of the quantum paraelectric EuTiO3 exhibits a sharp decrease at about 5.5 K, at which temperature antiferromagnetic ordering of the Eu spins simultaneously appears, indicating coupling between the magnetism and dielectric properties. A similar feature has also been detected in Eu1-xBaxTiO3 (0
Wu, Hua; Jiang, Qing; Shen, Wen Zhong
Microwave Dielectric Properties of Ceramic and Nanocomposite Titanates of Transition Metal
NASA Astrophysics Data System (ADS)
Ceramic and nanocomosite samples of the titanates of transition metals have been synthesized and their microwave dielectric properties have been investigated. Frequency and magnetic field dependences of the transmission and reflection coefficients in centimeter and millimeter wavebands were measured. It is established for most of studied ceramic titanates that transmission coefficient increases and reflection coefficient decreases when frequency increases. An absorption maximum has been found for ceramic sample made of Co0.9Fe0.1TiO3. The real and imaginary parts of complex dielectric permittivity were determined from measurements of transmission and reflection coefficients. On the whole, real part of dielectric permittivity of nanocomposite titanates based on an opal matrix is less than for ceramic titanates.
Rinkevich, Anatoly B.; Kuznetsov, Evgeny A.; Perov, Dmitry V.; Ryabkov, Yury I.; Samoylovich, Mikhail I.; Klescheva, Svetlana M.
NASA Astrophysics Data System (ADS)
Dielectric, thermal, and microhardness properties of high-performance barium titanate (BaTiO3)-filled polyetheretherketone (PEEK) composites were studied. BaTiO3 was varied from 0 vol.% to 67 vol.% in the PEEK matrix. The dielectric constant of the composites measured at 1 MHz increased approximately 14-fold. There was no dispersion in the dielectric constant with frequency between 10 kHz and 15 MHz. The Lichtenecker equation and modified Lichtenecker equation agreed well with the experimental data. The dissipation factor of the composites varied from 0.0056 to 0.0096. Scanning electron microscopy showed uniform dispersion of BaTiO3 in the matrix. The microhardness of the composites increased by more than 2.5-fold compared with pure PEEK. The coefficient of thermal expansion measured below and above the glass-transition temperature was reduced by up to 56%. These results make these composites promising candidate high-temperature organic substrates.
Goyal, R. K.; Madav, V. V.; Pakankar, P. R.; Butee, S. P.
3-D Static Elastic Constants and Strength Properties of a Glass/Epoxy Unidirectional Laminate
Tensile Yield Stress (MPa) 41.0 Ultimate Tensile Strength (MPa) 76.3 Ultimate Tensile Strain (%) 4.20 0.2% Offset Compressive Yield Stress (MPa) -64.7 Ultimate Compressive Strength (MPa) -91.0 Ultimate3-D Static Elastic Constants and Strength Properties of a Glass/Epoxy Unidirectional Laminate
Dielectric properties of the polar head group region of zwitterionic lipid bilayers.
A theoretical model describing the dielectric properties of the lipid membrane-water interface region was developed. The rotating polar head groups (e.g. phosphatidylcholine) were simulated as a collection of interacting dipoles imbedded in a nonhomogeneous dielectric. The interactions between the nearest neighborhood were explicitly taken into account, while the other interactions were evaluated by means of the continuum theories. The values of the dielectric constant, its anisotropy and the spontaneous polarization of the interface were evaluated. As an application, we calculated the energy of interaction between an ion and the membrane polar head group region. The results indicate a small spontaneous polarization of the interface (1-1.7 Debyes per lipid molecule) due to the tilting angle of the choline residue with respect to the membrane surface. This dipolar field partially compensates that of opposite orientation originating from the ester group region, giving calculated overall dipolar potentials in better agreement with the experimental data. Our model suggests also a very strong dielectric anisotropy of the interface region, the component of the dielectric constant perpendicular to the membrane plane being much smaller than the parallel component. PMID:3756297
Raudino, A; Mauzerall, D
Electrificationof Pressboard/Oil Interface and TransientPhenomena ABSTRACT The static electrificationphenomenonof and immersed in a metallic tank containing -4 1of oil; and second vice enables us to measure the electrostaticcharge tendency of oils. The electrostaticcharge ndency (ECT) of insulatingoilsand
Paris-Sud XI, Universit├® de
Dielectric and insulating properties of an acrylic DEA material at high near-DC electric fields
NASA Astrophysics Data System (ADS)
A number of adaptive structure applications call for the generation of intense electric fields (in excess of 70 MV/m). Such intense fields across the thickness of a thin polymer dielectric layer are typically used to exploit the direct electromechanical coupling in the form of a Maxwell stress: (see manuscript) Where V/d is the applied field, ?0 is the permittivity of vacuum and ? is the relative permittivity of the material. The field that can be applied to the dielectric is limited by the dielectric strength of the material. Below the limit set by the breakdown, the material is generally assumed to have a field independent dielectric constant and to be a perfect insulator, i.e. to have an infinite volume resistivity. While extensive investigations about the mechanical properties of the materials used for electronic Dielectric Elastomer Actuators (DEA) are available from literature, the results of the investigation of the insulating and dielectric properties of these materials, especially under conditions (electric field and frequency) similar to the ones encountered during operation are not available. In the present contribution, we present a method and a set-up for the measurement of the electric properties of thin polymer films, such as the ones used for the fabrication of electronic DEAs, under conditions close to operations. The method and setup where developed to investigate the properties of 'stiff' thin polymer films, such as Polyimide or Polyvinylidenefluoride, used for Electro-Bonded Laminates (EBLs). The properties of the well known VHB 4910 acrylic elastomer are presented to illustrate how the permittivity and the leakage current can be measured as a function of the electric field and the deformation state, using the proposed set-up. The material properties were measured on membranes under different fixed pre-stretch conditions (? 1, ?2=3, 4, 5), in order to eliminate effects due to the change in sample geometry, using gold sputtered electrodes, 20nm thick. The values obtained for the permittivity of the material are in good agreement with the work of other authors. The dissipative properties revealed by the measurements performed at high fields, similar to the ones encountered in operation, indicate that this less investigated aspect of VHB needs to be taken in consideration for real world applications.
Di Lillo, L.; Schmidt, A.; Bergamini, A.; Ermanni, P.; Mazza, E.
Pure (undoped) piezoelectric lead zirconate titanate (PZT) ceramic samples at compositions across the ferroelectric region of the phase diagram were prepared from sol-gel-derived fine powders. Excess lead oxide was included in the PZT powders to obtain dense (95-96% of theoretical density) ceramics with large grain size (>7 mum) and to control the lead stoichiometry. The dielectric, piezoelectric, and elastic properties were measured from 4.2 to 300 K. At very low temperatures, the extrinsic domain wall and thermal defect motions freeze out. The low-temperature dielectric data can be used to determine coefficients in a phenomenological theory. The extrinsic contribution to the properties can then be separated from the single-domain properties derived from the theory. PMID:18285000
Zhuang, Z Q; Haun, M J; Jang, S J; Cross, L E
Effect of erythrocytes oscillations on dielectric properties of human diabetic-blood
NASA Astrophysics Data System (ADS)
It has been demonstrated that the erythrocytes (RBCs) oscillate during their tank-treading motion with high-frequency oscillations. This oscillatory motion drastically affects the dielectric and electrical properties of RBCs. Moreover, the glucose level in blood affects the electrical and dielectric properties of blood. It has been, also, shown that the frequency of these oscillations exponentially decrease from 1.2 MHz down to 0.85 MHz with variation of glucose level from 85 mg/dL up to 346.1 mg/dL. It is expected that these oscillations strongly affect the general physiological properties of blood and would stimulate the curiosity of scientists and bioengineers to present new, more efficient, rapid, safe and viable diagnostic and/or therapeutic methods for blood disorders; in particular diabetes.
Abdalla, S.
Dielectric properties of (Ba, Nb) doped TiO 2 ceramics: Migration mechanism and roles of (Ba, Nb)
Ultrahigh relative dielectric constants with stable frequency and temperature dependence as well as relatively low loss tangent are found in barium and niobium doped TiO2 ceramics with a silver electrode. The roles of barium and niobium on the dielectric properties of the ceramics are explained after the migration mechanism and the influence of barium and niobium have been analysed. Both
Jenn-Ming Wu; Chi-Jen Chen
measurements of the elastic constants were performed using basically negative dielectric substances constants which determine the electro-optical performance of twisted nematic displays (TN-LCDs) [7] requires265 Class specific elastic, viscous, optical and dielectric properties of some nematic liquid
Paris-Sud XI, Universit├® de
NASA Astrophysics Data System (ADS)
High dielectric permittivity materials are much desirable in the electric industry. Filling polymer matrix with conductive powders to form percolative composites is one of the most promising methods to achieve high dielectric permittivity. However, they do not always provide high mechanical properties and thermal stability, which seriously limit their applications. In this study, we present the preparation of functional core-shell structured silver nanowires/polyimide (AgNWs/PI) hybrid film with high dielectric permittivity and low loss dielectric. The core-shell structure of AgNWs was characterized by transmission electric microscopy. The dynamical mechanical analysis showed that AgNWs/PI hybrid films had relative high dynamic mechanical properties with storage modules over 1 Gpa. Moreover, the hybrid films exhibited excellent thermal stability with 5 % weight-loss temperature above 500 ░C. The dielectric properties of the carbon-coated AgNWs hybrid films were remarkably improved. The maximum dielectric permittivity of hybrid films is 126 at 102 Hz, which was 39 times higher than that of pure PI matrix, while the dielectric loss of that is still remained at a low value. This study showed a new method to improve the dielectric, dynamic mechanical and thermal properties of films.
Wang, Lisi; Piao, Xiaoyu; Zou, Heng; Wang, Ya; Li, Hengfeng
Thermal, mechanical and dielectric properties of poly(vinyl alcohol)/graphene oxide composites
NASA Astrophysics Data System (ADS)
In this work the composite films of poly(vinyl alcohol) (PVA) doped with functionalized Graphene Oxide (GO) were prepared by solution casting method. The films were characterized using FT-IR, DSC, XRD, mechanical properties and dielectric studies at room temperature. FTIR spectra shows the formation of hydrogen bonds between hydroxyl groups of PVA and the hydroxy groups of GO. The DSC thermograms shows the addition of GO to PVA greatly improves the thermal stability of the composites. XRD patterns shows that the GO exfoliated and uniformly dispersed in PVA matrix. Mechanical properties are significantly improved in PVA/GO composites. The tensile strength increased from 8.2 to 13.7 MPa and the Young's modulus increased from 7.5 to 24.8 MPa for 5 wt% GO doped sample. Dielectric spectroscopy showed a highest dielectric constant for the 5 wt% GO doped PVA films. This work provides a potential design strategy on PVA/GO composite, which would lead to higher-performance, flexible dielectric materials, high charge-storage devices.
Rathod, Sunil G.; Bhajantri, R. F.; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Naik, Jagadish
Study Of Structural And Dielectric Properties Of Ni-Mg Ferrite Nanoparticles
Ferrite nanoparticles of basic composition Ni{sub 0.7}Mg{sub 0.3}Fe{sub 2-x}Al{sub x}O{sub 4}(0.0{<=}x{<=}0.5) were prepared through citrate gel method and characterized using XRD, TEM and dielectric spectroscopy techniques. The dielectric properties were studied as a function of frequency (42 Hz-5 MHz) at room temperature. The average particle size has been found between 8-17 nm. The dispersion in dielectric properties and ac conductivity ({sigma}{sub ac}), with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe{sup 2+} and Fe{sup 3+} as well as between Ni{sup 2+} and Ni{sup 3+} ions at B-sites. The dielectric loss tangent (tan {delta}) shows abnormal behavior for the compositions 0.3, 0.4 and 0.5 which has been explained in the light of Rezlescue model.
Nongjai, Razia; Batoo, Khalid Mujasam; Khan, Shakeel [Dept. of Applied Physics, Aligarh Muslim University, Aligarh, 202002 (India) and King Abdullah Institute for Nanotechnology, King Saud University, Riyadh, 11451 (Saudi Arabia)
The anomalies which occur in most static and dynamic physical property measurements on solutions of water in acetic acid can be used with critical analysis to infer associative molecular structures. The anomalies indicate significant structural changes. Proton magnetic resonance chemical shifts for acetic acid¢water solutions show a significant structural change occurring in the region of equal molar concentration. Literature values
Robert W. Sims; M. Robert Willicott III; R. R. Inners
The anomalies which occur in most static and dynamic physical property measurements on solutions of water in acetic acid can be used with critical analysis to infer associative molecular structures. The anomalies indicate significant structural changes. Proton magnetic resonance chemical shifts for acetic acid-water solutions show a significant structural change occurring in the region of equal molar concentration. Literature values
Robert W. Sims; M. Robert Willicott III; R. R. Inners
Characterization of material properties of low temperature curing polymer dielectrics
Mechanical properties are typically used as a first-order comparison of different thin film microelectronic polymers. Tensile testing is commonly used to determine such mechanical properties (i.e. YoungÆs modulus, % elongation, tensile strength). Having accurate values generated under known, standardized test conditions is therefore an important consideration. We have found that the method of sample preparation and fixturing during test, gage
Alan Huffman; Marianne Butler; Jeffrey Piascik; Philip Garrou; Jay Im
Fundamental Properties of Organic Low-k Dielectrics Usable in the Cu Damascene Process
NASA Astrophysics Data System (ADS)
The material parameters for organic low-k dielectrics usable in the damascene process were studied using two different types of polymers with similar low dielectric constants, namely, the PQ-600 thermoplastic polymer and the SiLK thermosetting polymer. The resistibility of these polymers in the damascene process was investigated through hard-mask (SiO2) deposition, etching and chemical mechanical polishing (CMP) processes using scanning probe microscopy (SPM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and a modified edge liftoff test (m-ELT). For the PQ-600 film, damage was observed in the deposition process and dissolution of the film occurred during chemical cleaning in the etching process. On the other hand, the SiLK film was combinable with the Cu damascene process and usable as an interlayer dielectric (ILD) in one-level Cu wiring. A high glass transition temperature (Tg) and chemical resistance resulting from the thermosetting structure are considered to be the essential properties required for the desired organic low-k dielectrics. In eddition, the electrical properies of the SiLK film were investigated using a one-level test element group (TEG) formed through a single Cu damascene process. The dielectric constant of the SiLK film extracted from the Cu damascene TEG compared with that of bulk SiO2 was reduced by 24%. The leakage current measured at 1 MV/cm between the adjoining Cu lines at the TEG pattern with a hard mask was 9.7ū 10-10 A/cm2, and dielectric breakdown occurred at 5.5 MV/cm.
Nomura, Yutaka; Ota, Fumihiko; Kurino, Hiroyuki; Koyanagi, Mitsumasa
Exploring Soil Properties through Electromagnetic Sensor-based Complex Dielectric Permittivity
NASA Astrophysics Data System (ADS)
Soil physical and chemical properties contain important information influencing soil quality as well as plant growth and yield, all of which ultimately impact hydrologic, ecologic and agricultural interests. Electromagnetic (EM) sensors are widely used for water content determination using a variety of measurement techniques, most of which are based on soil capacitance or travel-time analysis. Most measurements yield a single dielectric permittivity value (usually at an unknown frequency), which must be interpreted to derive the volumetric water content. Recent research associated with permittivity measurements in the frequency domain suggest that important soil features may be extracted there. The objectives of this work were to explore EM sensor-based frequency-domain measurements and their potential to reveal soil physical and chemical properties. Ten different EM sensors were evaluated using reference dielectric liquids and suspensions. Effective measurement frequencies for sensors outputing dielectric permittivity were estimated using spectra from network analyzer measurements. Eight different soils with varying texture were selected and permittivities were measured at different water contents to observe the potential for extracting soil properties from frequency-domain measurements. Measured permittivities using lower æfixedÆ frequency sensors were larger in proportion to the fineness of the soil texture than higher frequency, time domain reflectometry (TDR) measurements. In spite of the challenges in separating relaxation and polarization processes, permittivities determined using multiple frequencies (e.g., 50 and 500 MHz) show potential for illuminating soil textural and other soil properties.
Jones, S. B.; Wang, C.; Robinson, D. A.; Tuller, M.
NASA Astrophysics Data System (ADS)
The dielectric properties of (Nb, Y)-doped BaTiO3 in a multilayer ceramic capacitor (MLCC) under combined external uniaxial compressive stress and dc bias field were investigated at room temperature by using a modified Ginsburg-Landau-Devonshire thermodynamic theory and the dielectric measurement. It is found that although dc bias decreases the dielectric properties dominantly, the influence of the external uniaixial compressive stress should not be neglected. When applied along a direction perpendicular to the internal electrode layer in the MLCC, the external uniaixal compressive stress will strengthen the negative effect of dc bias. In contrast, the external uniaxial compressive stress along a direction parallel to the internal electrode layer in the MLCC will increase the dielectric permittivity under dc bias field, i.e. improve the ?-V response of the MLCC. Furthermore, although there is a difference between the calculated permittivity and the measured permittivity, the effects of the combined external uniaxial compressive stress and dc bias field on the dielectric permittivity described through two approaches are in good agreement.
Yang, Gang; Yue, Zhenxing; Sun, Tieyu; Gou, Huanlin; Li, Longtu
NASA Astrophysics Data System (ADS)
The temperature and frequency dependent dielectric properties of polycrystalline Cd-doped Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? ( y=0,0.25,0.5,0.75) bulk superconductor samples are investigated. The zero resistivity critical temperature { T c( R=0)} has decreased and normal state resistivity has increased with the increase of Cd-doping in Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? samples. The dielectric properties such as dielectric constants ( ?', ??), dielectric loss tangent (tan ?) and ac-conductivity ( ? ac ) are investigated by measuring the capacitance (C) and conductance (G) in the frequency range of 10 KHz to 10 MHz at different temperature from 80 K to 300 K. The negative capacitance (NC) is observed in all Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? samples. The large values of NC observed at lower frequencies and temperatures may be due to reduced thermal vibrations and enhanced polarizability of the material. The effect of Cd-doping on bulk properties, dc-resistivity ( ?) and ac-electrical conductivity ( ? ac ) of these superconductor samples are investigated. The polarization in Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? samples is most likely arising from the displacement of charges in CuO2/CdO2 planes relative to the static charges at Ba2+, Tl3+, and Cu2+ sites in Cu0.5Tl0.5Ba2O4- ? charge reservoir layers by external applied field.
Rahim, M.; Khan, Nawazish A.; Mumtaz, M.
Guiding properties of asymmetric hybrid plasmonic waveguides on dielectric substrates
We proposed an asymmetric hybrid plasmonic waveguide which is placed on a substrate for practical applications by introducing an asymmetry into a symmetric hybrid plasmonic waveguide. The guiding properties of the asymmetric hybrid plasmonic waveguide are investigated using finite element method. The results show that, with proper waveguide sizes, the proposed waveguide can eliminate the influence of the substrate on its guiding properties and restore its broken symmetric mode. We obtained the maximum propagation length of 2.49?ū?103Ā?m. It is approximately equal to that of the symmetric hybrid plasmonic waveguide embedded in air cladding with comparable nanoscale confinement. PMID:24406096
Dielectric Properties and Applications of CVD Diamonds in the Millimeter and Terahertz Ranges
NASA Astrophysics Data System (ADS)
The results of investigation of the dielectric properties in the millimeter and terahertz ranges of diamond samples prepared by using the direct current arc plasma jet (APJ) and the microwave plasma chemical vapour deposition (MPCVD) techniques are presented. Various methods for the measurements of the dielectric properties using high-Q open resonators and cylindrical cavity resonators are discussed while the activation energy of the conductivity and point defect parameters (such as concentration and activation energy of the defect induced levels) in both kinds of diamonds are studied via Conductivity and Charge-based Deep Level Transient Spectroscopy (Q-DLTS) measurements (for the first time in APJ diamond) and compared. The absorption mechanisms in these diamonds grown by different methods are discussed.
Garin, B. M.; Parshin, V. V.; Polyakov, V. I.; Rukovishnikov, A. I.; Serov, E. A.; Mocheneva, O. S.; Jia, Ch. Ch.; Tang, W. Z.; Lu, F. X.
Synthesis and dielectric properties of zinc oxide nanoparticles using a biotemplate
NASA Astrophysics Data System (ADS)
Zinc Oxide nanoparticles are synthesized using DNA as capping agent. Zinc oxide nanoparticles are synthesized using DNA as a capping agent. Structural and morphological characterizations are done using SEM, FTIR and XRD. The particle size and lattice parameters are calculated from the diffraction data. The optical properties are studied using UV-Vis absorption spectroscopy and bandgap variation with temperature is determined. The dielectric property of nanoparticles is studied by varying temperature and frequency. The dielectric constant and dispersion parameters are found out. Method of Cole-Cole analysis is used to study the high temperature dispersion of relaxation time. The variation of both AC and DC conductivity are studied and activation energy calculated.
P, Sharmila P.; Tharayil, Nisha J.
Nondestructive approach for measuring temperature-dependent dielectric properties of epoxy resins.
A practical method for measuring the complex relative permittivity of epoxy resins and other viscous liquids over a wide temperature range in S-band is presented. The method involves inserting a hot glass tube, filled with the liquid-under-test (LUT), into a length of WR-340 rectangular waveguide connected between two ports of a Vector Network Analyzer, which measures the reflection and transmission coefficients at 2.45 GHz. The heating arrangement consists of a temperature-controlled glycol bath, where the LUT-filled glass tube is placed. The dielectric properties are determined using an optimization routine, which minimizes the error between the theoretical and measured scattering coefficient data. The theoretical values of the scattering coefficient data are computed with the help of a numerical 3-D electromagnetic field simulator, the CST Microwave Studio. The dielectric properties of the empty glass tube (required by the simulation code) are also measured using the above methodology. PMID:19227067
Akhtar, M Jaleel; Feher, Lambert E; Thumm, Manfred
NASA Astrophysics Data System (ADS)
The semiconductor oxides SnO2, HfO2, ZrO2, TiO2 and SrTiO3 are interesting materials for applications as high-K dielectric gate materials in silicon-based devices and spintronics, among others. Here we review our theoretical work about the structural, electronic and vibrational properties of these oxides in their most stable structural phases, including dielectric properties as derived from the electronic structure taking into account the lattice contribution. Finally, we address the recent role played by the presence of transition metal atoms in semiconductor oxides, considering in particular SnO2 as an example in forming diluted magnetic alloys.
Scolfaro, L. M. R.; Leite Alves, H. W.; Borges, P. D.; Garcia, J. C.; da Silva, E. F., Jr.
Modeling of dielectric properties of aqueous salt solutions with an equation of state.
The static permittivity is the most important physical property for thermodynamic models that account for the electrostatic interactions between ions. The measured static permittivity in mixtures containing electrolytes is reduced due to kinetic depolarization and reorientation of the dipoles in the electrical field surrounding ions. Kinetic depolarization may explain 25-75% of the observed decrease in the permittivity of solutions containing salts, but since this is a dynamic property, this effect should not be included in the thermodynamic modeling of electrolytes. Kinetic depolarization has, however, been ignored in relation to thermodynamic modeling, and authors have either neglected the effect of salts on permittivity or used empirical correlations fitted to the measured static permittivity, leading to an overestimation of the reduction in the thermodynamic static permittivity. We present a new methodology for obtaining the static permittivity over wide ranges of temperatures, pressures, and compositions for use within an equation of state for mixed solvents containing salts. The static permittivity is calculated from a new extension of the framework developed by Onsager, Kirkwood, and Fr÷hlich to associating mixtures. Wertheim's association model as formulated in the statistical associating fluid theory is used to account for hydrogen-bonding molecules and ion-solvent association. Finally, we compare the Debye-H³ckel Helmholtz energy obtained using an empirical model with the new physical model and show that the empirical models may introduce unphysical behavior in the equation of state. PMID:23924202
Maribo-Mogensen, Bj°rn; Kontogeorgis, Georgios M; Thomsen, Kaj
Sintering and microwave dielectric properties of LTCC-zinc titanate multilayers
The effects of ZnO¢B2O3¢SiO2 (ZBS) on the sintering behavior and microwave dielectric properties of ZnO¢TiO2 system were investigated as a function of ZBS content and sintering temperature. Densities of the specimens were enhanced with an increase of ZBS up to 2 wt.% and then decreased. X-ray diffractometry analyses results indicated that the phase stability region of the hexagonal ZnTiO3 extended
Q. L. Zhang; H. Yang; J. L. Zou; H. P. Wang
Dielectric properties of zinc titanate thin films prepared by Rf magnetron sputtering
Zinc titanate thin films of ~500Ānm in thickness were synthesized by an RF magnetron sputtering using a sintered ceramic target.\\u000a After annealing in temperature ranges of 300¢800Ā░C, their phase transition and dielectric properties were investigated as\\u000a a function of annealing temperature. Crystalline ZnTiO3 phase was first detected at the annealing temperature of 500Ā░C within XRD detection limit though the sputtered
Jin Suk Jung; Young Ho Kim; Sang Keun Gil; Dong Heon Kang
Dielectric property of Ion Beam Enhanced Deposited lithium tantalate thin film infrared detector
The Ion Beam Enhanced Deposited (IBED) LiTaO3 thin film infrared detectors with Al\\/LiTaO3\\/Pt structure were prepared on the Pt\\/Ti\\/SiO2\\/Si(100) substrate. The crystallization, the film thickness, the dielectric properties, the leakage current and the anti-breakdown ability of the IBED LiTaO3 thin film infrared detector samples were investigated by the different annealing processes. The XRD measured results show that, the prepared samples
De-Yin Zhang; Wei Qian; Kun Li; Jian-Sheng Xie
The dielectric properties of alkyl monolayers with various chain lengths [CH3(CH2)n-1- (n=12, 14, 16, and 18)] covalently bonded to a hydrogen terminated n-type silicon (111) surface in a nanoscale region were evaluated using current sensing atomic force microscopy (AFM). A reliable electrical contact between the alkyl monolayers and the metal-coated AFM tip was achieved under slight stress. At a force
Jianwei Zhao; Kohei Uosaki
Lead zirconium titanate Pb (Zr0.58Ti0.42) O3 (PZT) thin films were deposited on silicon substrates by sol-gel process. The structural, morphological, dielectric and nano mechanical properties of these films have been studied systematically. The thicknesses of the films were around 160 nm. During the deposition of each layer, the films were baked in a microwave oven which in turn resulted in
A. Rambabu; K. Sudheendran; K. C. James Raju
Time-domain technique for measurement of the dielectric properties of oil shale during processing
A time-domain technique for the measurement of the dielectric properties of oil shale over a broad frequency range is described. The advantages of this technique, which can be used to study chemical changes occurring during the rapid heating of the shale, include simplicity of the procedure, relatively cheap equipment required, and the considerably shorter time to do the measurements as compared with frequency-domain methods. Preliminary results illustrate the feasibility of this method.
Iskander, M.F.; Tyler, A.L.; Elkins, D.F.
Effective electromagnetic properties of honeycomb substrate coated with dielectric or magnetic layer
NASA Astrophysics Data System (ADS)
Effective electromagnetic properties of aramid honeycomb board coated with a layer of multi-wall carbon nanotube or iron flakes composites were measured with waveguide method from 4 to 12 GHz. It was proved that homogenization theory could predict the effective permittivity or permeability of the honeycomb composites with good accuracy. The coated honeycomb composites of relatively high permittivity and permeability could potentially be used to develop dielectric or magnetic substrate for shielding layer or absorbing structures working at microwave frequencies.
Liu, L.; Fan, C. Z.; Zhu, N. B.; Zhao, Z. Y.; Liu, R. P.
character and the large values of the high frequency optical dielectric constants, E,, of the lead compounds, PbS, PbSe and PbTe, it was conjectured that the low frequency (static) dielectric constant, E constant [I]. This conjecture proved to be correct. The experimentally determined values of E, of PbS, Pb
Paris-Sud XI, Universit├® de
Microwave Dielectric Properties of Alfalfa Leaves From 0.3 to 18 GHz
Dielectric properties (i.e., permittivity) are essential in designing, simulating, and modeling microwave applications. The permittivity of stacked leaves of alfalfa (Medicago sativa) were measured with a network analyzer and a coaxial probe, and the effect of moisture content (MC: 12% 73% wet basis), frequency (300 MHz to 18 GHz), bound water (Cole Cole dispersion equation), temperature ( 15 C and 30 C), leaf-orientation, and pressure (0 11 kPa) were investigated. The measured permittivity increased with MC. A critical moisture level (CML) of 23% was reported, below which the permittivity decreased with increasing frequency at 22 C. Above CML and up to 5 GHz, the dielectric constants followed the Cole Cole dispersion, and the dielectric loss factors consisted of ionic and bound water losses. Above 5 GHz, the behavior of the dielectric constant was similar to that of free water, and the polar losses became dominant. Above 0 C, the measured permittivity followed a trend similar to that of free saline water and was characterized by the Debye equation. Below 0 C, it was dominated by nonfreezing bound and unfrozen supercooled moistures. The relaxation parameters and the optimum pressure (9 kPa) for the leaf measurements were determined. The effects of variations among the samples, and their orientations had negligible effects on the measured permittivity.
Sokhansanj, Shahabaddine [ORNL; Shrestha, Bijay [University of Saskatchewan; Wood, H.C. [University of Saskatchewan
Manifestation of magnetic quantum fluctuations in the dielectric properties of a multiferroic.
Insulating magnets can display novel signatures of quantum fluctuations as similar to the case of metallic magnets. However, their weak spin-lattice coupling has made such observations challenging. Here we find that antiferromagnetic (AF) quantum fluctuations manifest in the dielectric properties of multiferroic Ba2CoGe2O7, where a ferroelectric polarization develops concomitant to an AF ordering. Upon application of a magnetic field (H), dielectric constant shows a characteristic power-law dependence near absolute zero temperature and close to the critical field Hc=37.1?T due to enhanced AF quantum fluctuations. When H>Hc, the dielectric constant shows the temperature-dependent anomalies that reflect a crossover from a field-tuned quantum critical to a gapped spin-polarized state. We uncover theoretically that a linear relation between AF susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum criticality in condensed matter. PMID:25072808
Kim, Jae Wook; Khim, Seunghyun; Chun, Sae Hwan; Jo, Y; Balicas, L; Yi, H T; Cheong, S-W; Harrison, N; Batista, C D; Han, Jung Hoon; Kim, Kee Hoon
Dielectric, piezoelectric, and ferroelectric properties of lanthanum-modified PZTFN ceramics
NASA Astrophysics Data System (ADS)
Specimens of Pb1-1.5 x La x (Zr0.53Ti0.47)1- y- z Fe y Nb z O3 ( x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01) (PZTFN) ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal (space group P4 mm) and rhombohedral (space group R3 c) phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hysteresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response at x ? 0.012, which corresponds to the morphotropic phase boundary (MPB).
Kumar, Arvind; Mishra, S. K.
Optical, dielectric and electrical properties of PVA doped with Sn nanoparticles
NASA Astrophysics Data System (ADS)
Films of pure and doped polyvinyl alcohol (PVA) with different concentrations of Sn nanoparticles (??100 nm) were prepared using casting technique. The effect of Sn addition on micro-structural, optical, electrical and dielectric properties of PVA was investigated. Microstructure of Sn/PVA nanocomposite films was characterized by scanning electron microscopy (SEM). Dielectric properties and ac conductivity measurements were carried out at room temperature over a wide range of frequencies ranging from 50 Hz to 5 MHz. AC conductivity was found to increase with frequency. Besides, addition of Sn nanoparticles to PVA leads to a change in conductivities of the films. Coulomb blockade effect was found to dominate at certain concentrations of Sn which may be used to explain the obtained results. The dielectric properties of the Sn/PVA films were also investigated and results were discussed in correlation with the relevant models. The frequency dependence of the imaginary part of complex electric modulus for the Sn/PVA composites shows a loss peak attributed to interfacial polarization at a certain frequency. Optical energy gap of Sn/PVA films was determined and found to decrease for Sn concentrations up to 20% due to the interaction between the Sn nanoparticles and the host polymeric network leading to the creation of new molecular dipoles. For higher Sn concentrations, the optical energy gap starts to increase which may be resulting from structural changes leading to passivation of localized states near the band edges and hence widening of the energy gap.
Amin, G. A. M.; Abd-El Salam, M. H.
Valence and Core Electron Energy Loss Spectroscopy (VEELS and CEELS) experiments are performed from nanocrystallized nickel silicide thin films. Three different silicide compounds are identified in the films. Their chemical compositions are determined from Ni-L(2,3) to Si-K core edges quantification. The results obtained are coherent within less than 2% error with the pure Ni2Si, NiSi and NiSi2 phases. The analysis of the shape and energy position of Ni-L(2,3) near edge structures and volume plasmon peaks indicates that both are reliable signatures to identify unambiguously each compound. Nickel silicides low-loss spectra have been submitted as references to the EELS database (www.cemes.fr~eelsdb). Low-loss spectra are processed to extract single scattering spectra and determine the dielectric function. The results show that nickel silicides dielectric functions deduced from VEELS are in quite good agreement with epsilon1 and epsilon2 deduced from ellipsometry experiments. The optical properties (refractive index (n), absorption coefficient (k), reflectivity (R%) and resistivity (rho(opt))), calculated from VEELS dielectric function are then compared in details with the data resulting from others techniques available in the literature. We show that, except some minor divergences, the nickel silicides optical properties are generally well reproduced. This indicates that VEELS is a relevant technique for accessing reliably to physical properties and can be a successful alternative to conventional techniques when high spatial resolution is needed. PMID:16564176
Cheynet, M C; Pantel, R
Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates.
Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates are investigated using a finite-element method. Au and Ag are selected as plasmonic materials for nanowire waveguides with diameters down to 5-nm-level. Typical dielectric materials with relatively low to high refractive indices, including magnesium fluoride (MgF2), silica (SiO2), indium tin oxide (ITO) and titanium dioxide (TiO2), are used as supporting substrates. Basic waveguiding properties, including propagation constants, power distributions, effective mode areas, propagation distances and losses are obtained at the typical plasmonic resonance wavelength of 660 nm. Compared to that of a freestanding nanowire, the mode area of a substrate-supported nanowire could be much smaller while maintaining an acceptable propagation length. For example, the mode area and propagation length of a 100-nm-diameter Ag nanowire with a MgF2 substrate are about 0.004 ?m2 and 3.4 ?m, respectively. The dependences of waveguiding properties on geometric and material parameters of the nanowire-substrate system are also provided. Our results may provide valuable references for waveguiding dielectric-supported metal nanowires for practical applications. PMID:23038541
Wang, Yipei; Ma, Yaoguang; Guo, Xin; Tong, Limin
Water is a major component of fluids in the EarthÆs mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties greatly limits our ability to model water¢rock interactions and, in general, our understanding of aqueous fluids below the EarthÆs crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the EarthÆs upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)Śinsoluble in water under ambient conditionsŚbecomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. Our results suggest that aqueous carbonates could leave the subducting lithosphere during dehydration reactions and could be injected into the overlying lithosphere. The EarthÆs deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones. PMID:23513225
Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri A.; Galli, Giulia
Dielectric properties of halloysite and halloysite-formamide intercalate
NASA Astrophysics Data System (ADS)
Due to a high increase in electromagnetic pollution, the protection from non-ionizing electromagnetic radiation (EMR) represents an important problem of contemporary environmental science. We are searching for natural materials with the potential for EMR screening. We have discovered that hydro-halloysite has interesting properties as an EMR absorber. Unfortunately, it is a very unstable material. Drying it for even a short period of time leads to the loss of desired properties. In the paper, we have demonstrated that the intercalation of halloysite (the process of introducing guest molecules into the mineral structure) makes it possible to recover the ability to absorb an electromagnetic wave and obtain a promising material for electromagnetic field shielding applications.
Adamczyk, M.; Rok, M.; Wolny, A.; Orzechowski, K.
Ultrawideband (UWB) microwave radar imaging techniques for breast cancer detection typically require estimates of the spatially averaged dielectric properties of breast tissue. We propose an algorithm for estimating patient-specific, frequency-dependent average dielectric properties from scattered UWB microwave signals. The algorithm is a variation of an iterative finite-difference time-domain (FDTD) technique for solving the time-domain inverse scattering problem. The assumption is
David W. Winters; Essex J. Bond; Barry D. Van Veen; Susan C. Hagness
Two modifications of lead titanate ceramic and the polyetherketoneketone polymer (PEKK) have been used to obtain two polymer\\/ceramic composites. The piezo-, pyro-, ferroelectric, and dielectric properties were studied. The calcium modified lead titanate\\/polyetherketoneketone (PTCa\\/PEKK) composite shows better piezo- and pyro-electric properties than that of the samarium and manganese modified lead titanate\\/polyetherketoneketone (PSTM\\/PEKK) composite. Also, a lower dielectric permittivity and remanent
A. Pelßiz-Barranco; P. Marin-Franch
Static and impact crack properties of a high-strength steel welded joint
In order to gain the benefits of weldable high-strength steels in pressurized equipment applications, satisfactory toughness and crack properties of the welded joint, both in the weld metal and the heat-affected ¢zone (HAZ), are required. Experimental investigations of toughness and crack resistance parameters through static and impact tests of a high-strength, low-alloy steel (HSLA) with a nominal yield strength of
M. Zrilic; V. Grabulov; Z. Burzic; M. Arsic; S. Sedmak
Static properties of a non-neutral Be-9(+)-ion plasma
NASA Technical Reports Server (NTRS)
The paper reports measurements of the static properties of laser-cooled nonneutral Be-9(+)-ion plasmas stored in Penning traps (PT) under a variety of experimental conditions. The shape, rotation frequency, density, and temperature of the ions were measured as functions of the PT potential and laser-cooling configuration. Within experimental error, the ion plasmas rotate without shear and exhibit approximate thermal equilibrium.
Brewer, L. R.; Bollinger, J. J.; Itano, Wayne M.; Larson, D. J.; Prestage, J. D.
Static dipole polarizabilities for the ground-state geometries of yttrium clusters (Yn, n <= 15) are investigated by using the numerically finite field method in the framework of density functional theory. The structural size dependence of electronic properties, such as the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) gap, ionization energy, electron affinity, chemical hardness and softness, etc., has been
Xi-Bo Li; Hong-Yan Wang; Ran Lv; Wei-Dong Wu; Jiang-Shan Luo; Yong-Jian Tang
NASA Astrophysics Data System (ADS)
We investigate the magnetic, dielectric, and magnetodielectric properties of rare-earth-substituted Aurivillius phase Bi6Fe1.4Co0.6Ti3O18. The room-temperature ferromagnetic behavior is observed in all samples, and the rare-earth-substituted samples exhibit an enhanced magnetization. The weak ferromagnetism can be ascribed to the spin canting of the antiferromagnetic coupling of the Fe-based and Co-based sublattices via Dzyaloshinsky-Moriya interaction. The dielectric loss of all samples exhibits two dielectric relaxation peaks corresponding to two different relaxation mechanisms. One relaxation process with Ea = 0.5 eV is related to the hoping process of oxygen vacancies and the other one with Ea = 1.6 eV can be ascribed to the intrinsic conduction. The Gd-doped sample exhibits a remarkable magnetodielectric effect (9.4%) at RT implying this Aurivillius phase may be the potential candidate for magnetodielectric applications.
Zuo, X. Z.; Yang, J.; Song, D. P.; Yuan, B.; Tang, X. W.; Zhang, K. J.; Zhu, X. B.; Song, W. H.; Dai, J. M.; Sun, Y. P.
Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films
Pb{sub 0.4}Sr{sub 0.6}TiO{sub 3} (PST) thin films doped with various concentration of Bi were prepared by a sol-gel method. The phase status, surface morphology and dielectric properties of these thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer, respectively. Results showed that the thin films with the maximum dielectric constant and minimum dielectric loss were obtained for x=0.15. For x<0.15, only pure PST perovskite phase were in the thin films. For 0.2
Li, X.T. [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Du, P.Y., E-mail: email@example.com [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Zhao, Y.L.; Tu, Y.; Dai, J.L.; Weng, W.J.; Han, G.R.; Song, C.L. [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)
Static and dynamic properties of the classical XY chain in a transverse magnetic field
NASA Astrophysics Data System (ADS)
We present extensive computer-simulation results for the static and dynamic properties of the one-dimensional classical XY model in a symmetry-breaking magnetic field. In-plane solitons are directly observed and their density is determined as a function of field and temperature. The bulk properties and the scattering function S(q,?) are also determined, but while they show spin-wave contributions they do not provide any clear evidence of soliton behavior. Our simulation results are compared with theoretical predictions.
Gerling, R. W.; Landau, D. P.
Dielectric relaxation and magnetic properties of Cr doped GaFeO3
NASA Astrophysics Data System (ADS)
Polycrystalline GaFe1-xCrxO3 (x = 0.05, 0.1 and 0.15) samples were prepared by solid state reaction. The monophasic compounds crystallize in the orthorhombic space group Pc21n and the unit cell volume decreases with increasing Cr content. The saturated magnetization and magnetic transition temperature of the ceramics decrease due to the dilution of the magnetic interaction with Cr concentration. The dielectric properties were investigated from 133 to 353 K at various frequencies (100-107 Hz). Whereas the dielectric constant decreases with Cr content an increase in dielectric loss tangent was observed. The activation energies of the compounds (calculated both from loss and modulus spectrum) are the same and have values ~0.22 eV and 0.27 eV for Cr = 10% and 15%, respectively, and hence the relaxation process may be attributed to the same type of charge carrier. A separation of the grain and grain boundary properties has been achieved using an equivalent circuit model. The capacitance and resistances associated with the grain boundary were found to be higher than those associated with grain.
Bakr Mohamed, M.; Wang, H.; Fuess, H.
Patterns of power absorption in a microwave oven for a range of dielectric properties of relevance to food processing were investigated. The governing Maxwell's equations with boundary conditions and a TE10 excitation were solved using a finite element method. Food properties were varied from values at their frozen state to values at high temperatures, as would be typical in a thawing process. For low-loss materials such as frozen foods, the high quality factor makes the heating significantly higher only when the size and shape of the load permit a dielectric cavity resonance in the load. Otherwise, the heating pattern will follow the modal electric field pattern of the oven. For moderate loss materials, the patterns will come from the modes of the dielectric cavity. The bandwidths of these modes are larger than the low-loss situation and their overlap results in a heating pattern that is somewhat more uniform. For high-loss materials, the concept of modes is no longer useful as the very large number of modes strongly overlap. The rapidly decaying field and power loss in the high-loss material can probably be characterized as an exponential decay. PMID:9177015
Peyre, F; Datta, A; Seyler, C
The microwave emissivity of relatively low-loss media such as snow, ice, frozen ground, and lunar soil is strongly influenced by fine-scale layering and by internal scattering. Radiometric data, however, are commonly interpreted using a model of emission from a homogeneous, dielectric halfspace whose emissivity derives exclusively from dielectric properties. Conclusions based upon these simple interpretations can be erroneous. Examples are presented showing that the emission from fresh or hardpacked snow over either frozen or moist soil is governed dominantly by the size distribution of ice grains in the snowpack. Similarly, the thickness of seasonally frozen soil and the concentration of rock clasts in lunar soil noticeably affect, respectively, the emissivities of northern latitude soils in winter and of the lunar regolith. Petrophysical data accumulated in support of the geophysical interpretation of microwave data must include measurements of not only dielectric properties, but also of geometric factors such as finescale layering and size distributions of grains, inclusions, and voids. ?? 1976 Birkha??user Verlag.
England, A.W.
Dielectric properties and conductivity in CuO and MoO 3 doped borophosphate glasses
NASA Astrophysics Data System (ADS)
A novel set of glasses of the type (B 2O 3) 0.10-(P 2O 5) 0.40-(CuO) 0.50-x-(MoO 3) x, 0.05? x?0.50, have been investigated for dielectric properties in the frequency range 100 Hz-100 kHz and temperature range 300-575 K. From the total conductivity derived from the dielectric spectrum the frequency exponent, s, and dc and ac components of the conductivity were determined. The temperature dependence of dc and ac conductivities at different frequencies was analyzed using Mott's small polaron hopping model, and the high temperature activation energies have been estimated and discussed. The observed initial decrease in conductivity (ac and dc) and increase in activation energy with the addition of MoO 3 have been understood to be due to the hindrance offered by the Mo + ions to the electronic motions. The observed peak-like behavior in conductivity (dip-like behavior in activation energy) in the composition range 0.20-0.50 mol fractions of MoO 3 may be due to mixed transition effect occurring in the present glasses. The temperature dependence of frequency exponent, s, has been analyzed using different theoretical models. It is for the first time that the mixed transition metal ion (TMI) doped borophosphate glasses have been investigated for dielectric properties and conductivity over wide temperature and frequency ranges and the data have been subjected to a thorough analysis.
Vijaya Kumar, B.; Sankarappa, T.; Kumar, Santosh; Prashant Kumar, M.; Sadashivaiah, P. J.; Ramakrishna Reddy, R.
NASA Astrophysics Data System (ADS)
The Bruggeman and Maxwell-Garnett effective medium approximations have been used widely to investigate optical properties of many different composite materials. In most cases, the effective medium approximation assumptions are based on random unit cell models in which some metal particles are embedded in a dielectric medium. The shapes of the embedded particles can be varied between spherical, ellipsoidal and cylindrical shapes. A new and interesting structure of connected short chains of completely amorphous carbon intermixed with short chains of silica at nanoscale level has been observed recently. A generalised Bergman representation based on an arbitrary spectral density function is currently applied on these carbon-in-silica samples with a reasonable success of fitting between experiment and theory. The curve-fitting procedure adopted here has resulted in information such as volume fraction of carbon relative to silica, percolation threshold, the thickness and effective dielectric function of the composite layer.
Katumba, G.; Forbes, A.
NASA Technical Reports Server (NTRS)
The characteristics of satellites are influenced by the electrical properties of the dielectric exterior. It was found in simulated space environment tests that the electrical conductivities of dielectrics are affected as the result of interactions with various components of the environment. The degree to which the conductivity was affected varied with material. In some instances the changes found to occur could be used to advantage, particularly if they could be enhanced. For example, the increased electrical conductivity of Kapton resulting from solar illumination could be used to advantage to eliminate the charge storage leading to electrical breakdown during magnetic substorms. Similarly the relative immunity of FEP Teflon to change from response to the space environment makes it a logical choice as a solar cell cover in a high-voltage solar array.
Nanevicz, J. E.; Adamo, R. C.; Grier, N.
NASA Astrophysics Data System (ADS)
Triglycine sulfate-gelatin (TGS-gelatin) films were grown by evaporation of the water from a solution containing gelatin and TGS. The pyroelectric and dielectric properties of the films were highly dependent on their water content. Moist films had higher pyroelectric coefficients and lower coercive fields than dry films. The dielectric permittivity increased strongly with an increase of water content and had a fractional power frequency dependence. The results are explained using a model of the TGS-gelatin film structure in which the gelatin phase is a superionic conductor or solid electrolyte. Absorption of water causes the formation of electric double layers at the electrode film and TGS crystallite-gelatin phase interfaces.
Khutorsky, V. E.; Lang, Sidney B.
Knowledge of the distribution of permeability and porosity in a reservoir is necessary for the prediction of future oil production, estimation of the location of bypassed oil, and optimization of reservoir management. The volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade. The techniques developed in this research will make it easier to use all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. In this project, we have developed computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Specifically, we have developed methods for adjusting porosity and permeability fields to match both production and time-lapse seismic data and have also developed a procedure to adjust the locations of boundaries between facies to match production data. In all cases, the history matched rock property fields are consistent with a prior model based on static data and geologic information. Our work also indicates that it is possible to adjust relative permeability curves when history matching production data.
Albert C. Reynolds; Dean S. Oliver; Yannong Dong; Ning Liu; Guohua Gao; Fengjun Zhang; Ruijian Li
Effect of Sintering Temperature on Dielectric Properties of Iron Deficient Nickel-Ferrite
Nickel Ferrite among all the magneto ceramic materials have been studied very much due to its large number of applications. But there is a large scope of modification of its properties. Thus people still working on it for improvisation of its properties via compositional and structural modifications. Present paper reporting the preparation and characterization of iron deficient Nickel ferrite for different sintering temperature. Ferrite samples having the general formula NiFe1.98O{sub 4} were prepared using the standard ceramic method. The phase formation was confirmed by X-ray diffraction technique. The effect of sintering temperature on the electrical properties and resistivity was studied. The data shows that dielectric properties are highly dependent on the sintering temperature.
Rani, Renu [Electroceramics Research Lab, GVM Girls College, Sonepat-131001 (India); School of Physics and Material Science, Thapar University, Patiala-147004 (India); Singh, Sangeeta [Department of Physics, GVM Girls College, Sonepat-131001 (India); Juneja, J. K. [Department of Physics, Hindu College, Sonepat-131001 (India); Prakash, Chandra [Directorate of ER and IPR, DRDO, DRDO Bhawan, New Delhi-110105 (India); Raina, K. K. [School of Physics and Material Science, Thapar University, Patiala-147004 (India)
Measurement of the dielectric properties of high-purity sapphire at 1.865 GHZ from 2-10 Kelvin
A dielectric test cavity was designed and tested to measure the microwave dielectric properties of ultrapure sapphire at cryogenic temperatures. Measurements were performed by placing a large cylindrical crystal of sapphire in a Nb superconducting cavity operating in the TE01 mode at 1.865 GHz. The dielectric constant, heat capacity, and loss tangent were all calculated using experimental data and RF modeling software. The motivation for these measurements was to determine if such a sapphire could be used as a dielectric lens to focus the magnetic field onto a sample wafer in a high field wafer test cavity. The measured properties have been used to finalize the design of the wafer test cavity.
N. Pogue, P. McIntyre, Akhdiyor Sattarov, Charles Reece
NASA Astrophysics Data System (ADS)
Nanocomposites were prepared from polypropylene (PP) and untreated multiwalled carbon nanotubes (MWCNTs) or MWCNTs surface-functionalized with ionic liquids (MIL), as fillers, and their dielectric properties were compared. The physical (cation-?/?-?) interaction between the ionic liquids and the MWCNTs was apparent from Raman spectroscopy and from thermogravimetric analysis. Morphology characterization revealed that ionic liquids improve the dispersibility of MWCNTs in the PP matrix. It is suggested that the substantial increase in the dielectric permittivity of the nanocomposites compared with that of the PP originates from a remarkable Maxwell-Wagner-Sillars (MWS) effect at percolation threshold where mobile charge carriers are blocked at internal interfaces between the MIL and the PP matrix. The high polarity of ionic liquids may reinforce the MWS effect, and the nonconducting organic groups of the ionic liquids promote the low loss tangent and low conductivity of the MIL/PP nanocomposites. Compared with MWCNTs/PP nanocomposites, lower loss tangent and higher dielectric permittivity were observed for MIL/PP nanocomposites, making the material more attractive for application in electronics.
Xu, Pei; Gui, Haoguan; Hu, Yadong; Bahader, Ali; Ding, Yunsheng
Electrical and dielectric properties of silver iodide doped selenium molybdate glassy conductors
NASA Astrophysics Data System (ADS)
Electrical conductivity and dielectric properties of silver iodide doped silver ion mixed-former conducting glasses have been studied in this paper. The frequency dependence of conductivity has been analyzed following the random free-energy barrier model. The charge carrier relaxation time and the activation energy for relaxation have been determined for the present glasses. The applicability of Barton-Nakajima-Namikawa relation has been tested for the present glasses using the results obtained from random free-energy barrier model. The scaling of the conductivity spectra has been performed to understand the effect of temperature as well as composition on the relaxation dynamics. The dielectric data have been analyzed employing the Cole-Cole function, and parameters such as dielectric strength and Cole-Cole exponent have been obtained. The electrode polarization phenomenon for the present glass samples has been studied depending on temperature as well as composition. The different characteristic transitions concerning electrode polarization related to the charge transport at the interface have been obtained and are correlated to the bulk behavior. An estimation of the dc conductivity has been obtained using the result obtained from electrode polarization study and is observed to be very close to the experimental values.
Palui, A.; Deb, B.; Ghosh, A.
Thickness dependence of the dielectric properties of thermally evaporated Sb2Te3 thin films
NASA Astrophysics Data System (ADS)
Sb2Te3 thin films of different thickness (23 - 350 nm) were prepared by thermal evaporation technique. The thickness dependence of the ac conductivity and dielectric properties of the Sb2Te3 films have been investigated in the frequency range 10 Hz- 100 kHz and within the temperature range 293-373K. Both the dielectric constant epsilon1 and dielectric loss factor epsilon2 were found to depend on frequency, temperature and film thickness. The frequency and temperature dependence of ac conductivity (?ac(?)) has also been determined. The ac conductivity of our samples satisfies the well known ac power law; i.e., ?ac(?) propto ?s where s<1 and independent of the film thickness. The temperature dependence of ac conductivity and parameter s is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energies were evaluated for various thicknesses. The temperature coefficient of the capacitance (TCC) and permitivity (TCP) were determined as a function of the film thickness. The microstructure of the samples were analyzed using X-ray diffraction (XRD). This results are discussed on the base of the differences in their morphologies and thicknesses. The tendency for amorphization of the crystalline phases becomes evident as the film thickness increases.
Ulutas, K.; Deger, D.; Yakut, S.
Bone dielectric properties (DP) have been extensively studied. However, little literature has reported DP of bone from identical anatomical site under different status and its correlation with microstructure. Therefore, interrelationship between DP and microstructure of rat femurs with varying bone qualities (normal, osteoporotic and partially osteoporotic) was investigated. Diabetic osteoporosis was induced by streptozotocin (STZ) injection. 8 normal rats as control group together with 16 diabetic rats equally assigned to diabetes mellitus (DM) and DM treated by pulsed electromagnetic fields (PEMF) (DMĀ+ĀPEMF) group were used. DMĀ+ĀPEMF group was daily exposed to PEMF of 15ĀHz, 1ĀmT for 8Āweeks. After sacrifice, the femurs were harvested for microCT analysis and dielectric measurements (from 10ĀHz to 1ĀMHz). It was found that DP (conductivity and permittivity) altered after PEMF stimulation improved femoral microstructures (pĀ<Ā0.01). Significant correlations were found between microstructure indices (MI) and conductivity in the full frequency range (|r|Ā?Ā0.64, nĀ=Ā24) as well as permittivity in middle and low frequencies (|r|Ā?Ā0.52, nĀ=Ā24, from 1ĀHz to 1ĀkHz). The findings demonstrated the good correlation between DP and MI of femoral bone in rats, which makes it possible to distinguish bone under different status and predict MI variation through dielectric measurements. PMID:24710797
Tao, Feng; Fu, Feng; You, Fusheng; Ji, Zhenyu; Wen, Jun; Shi, Xuetao; Dong, Xiuzhen; Yang, Min
A Study of the Dielectric Properties of Dry and Saturated Green River Oil Shale
We measured dielectric permittivity of dry and fluid-saturated Green River oil shale samples over a frequency range of 1 MHz to 1.8 GHz. Dry sample measurements were carried out between room temperature and 146 C, saturated sample measurements were carried out at room temperature. Samples obtained from the Green River formation of Wyoming and from the Anvil Points Mine in Colorado were cored both parallel and perpendicular to layering. The samples, which all had organic richness in the range of 10-45 gal/ton, showed small variations between samples and a relatively small level of anisotropy of the dielectric properties when dry. The real and imaginary part of the relative dielectric permittivity of dry rock was nearly constant over the frequency range observed, with low values for the imaginary part (loss factor). Saturation with de-ionized water and brine greatly increased the values of the real and imaginary parts of the relative permittivity, especially at the lower frequencies. Temperature effects were relatively small, with initial increases in permittivity to about 60 C, followed by slight decreases in permittivity that diminished as temperature increased. Implications of these observations for the in situ electromagnetic, or radio frequency (RF) heating of oil shale to produce oil and gas are discussed.
Sweeney, J; Roberts, J; Harben, P
Structure-property investigations with dielectric study on phosphorylcholine-based polyurethane.
Polyurethane with zwitterionic phosphorylcholine on the main chain was synthesized and the structures were defined with FTIR and (1)HNMR. The mechanical (tensile strength, elastic modulus) and biological (platelet adhesion) evaluations of its blend films with polyurethane were of satisfactory results, which were in accordance with the requirements of the medical devices, showing their potential applications as anticoagulant biomaterials. The dielectric spectroscopy was recorded with solid films and with films in water. The dielectric dispersion of the solid films demonstrated the existence of condensed ionic structures, which lead to the rigidity enhancement of the soft segment of the phosphorylcholine-based polyurethane, so that its elastic modulus increased. The dielectric measurement with films in water, providing a measurement for the surface properties in the aqueous environment, offered a semiquantitative description of the interface dynamics of the material with a double-layer model, based on which a new hypothesis on the mechanism of blood or bio-compatibility was proposed that the hydrated surface of the satisfactory biomaterials can response to the outside electromagnetic stimuli with slight strength and prompt relaxation. PMID:22488801
Zhang, Qi; Zhu, Dan; Su, Fu; Xie, Yun; Ma, Zhenmao; Shen, Jian
High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers
NASA Technical Reports Server (NTRS)
Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.
Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.
Amorphous carbon nitride (a-CNx) films made by a reactive sputtering of a carbon target with nitrogen plasma shows high resistivity and high electrical breakdown field. Therefore, a-CNx is a good material as a dielectric material. In this paper, the effects of hydrogen-plasma and oxygen-plasma treatment to the dielectric properties of a-CNx films were studied, discussed and compared. A cyclic process
Masami Aono; Yohko Naruse; Shoji Nitta; Takashi Katsuno
The dielectric properties of 4,6-dimethyldibenzothiophene (DMDBT), hexadecane (HD), quinoline (QL), and HD\\/QL mixtures were investigated at six microwave frequencies (0.4, 0.9, 1.4, 1.9, 2.5 and 3.0GHz) and temperatures ranging from 297K to 624K. While both DMDBT and HD exhibited limited response under these conditions, QL demonstrated high dielectric loss with a penetration depth comparable to that of water. Through the
Adam A. Donaldson; Ronald Hutcheon; Zisheng Zhang
The effect of ZrO 2 doping on mechanical and dielectric properties of Al 2O 3 and MgAl 2O 4
NASA Astrophysics Data System (ADS)
Different samples of zirconia-doped alumina and spinel ceramics have been obtained and characterized. Their mechanical and dielectric properties at high frequencies have been measured. The dependence of these properties on the concentrations of the different zirconia phases is discussed. From the results obtained it is concluded that the dispersion of tetragonal zirconia particles in the ceramics causes strength and toughness to be improved without almost any degradation in dielectric properties, while monoclinic zirconia increases the dielectric loss.
Mollß, J.; Ibarra, A.; Frost, H. M.; Clinard, F. W.; Kennedy, J. C.; de Castro, M. Jimķnez
Estimating Layer Dielectric Properties in the Martian NPLD using SHARAD data
NASA Astrophysics Data System (ADS)
The polar caps of Mars are thought to represent a thorough history of the planet's paleoclimate for the Late Amazonian period. Specifically, the north polar layered deposits (NPLD), which are comprised of many sub-parallel layers of water ice with varying dust content, likely contain a climate signal related to the hydrologic cycle of Mars. Internal reflections in radar sounding data from the Shallow Radar (SHARAD) instrument on the Mars Reconnaissance Orbiter (MRO) presumably result from this vertical variation in dust content. Using these reflections, it is possible to produce estimates of the dielectric properties of the layers. These estimates may eventually be used to determine the dust concentration as a function of depth (age) in the NPLD and provide much-needed constraints for climate models. Although the bulk dielectric properties of the NPLD have been previously constrained by SHARAD, leading to an estimate of 5% overall dust fraction (Grima et al. 2008), discrete layers have not been analyzed. Rather than small changes in dust content between layers of water ice, we hypothesize that reflectors are instead caused by lag deposits of nearly pure dust cemented between ice layers. Using the simple plane wave propagation model put forward by Lauro et al. (2012) it is possible to use the power reflected at the surface relative to the power reflected at a subsurface interface in order to estimate the real part of the dielectric constant at the subsurface boundary. Using this technique we have calculated and mapped estimates of the dielectric constant for multiple layers in the Gemina Lingula region of the NPLD. Preliminary results support the lag deposit hypothesis, with dielectric constant estimates close to 5 in most areas, which is well above the expected value of water ice and falls within the values expected from dust-dominated layers. With further refinements to the model, as well as increased coverage in both depth (time) and geographic extent , we hope to be able to extend these results to the NPLD as a whole.
Lalich, D.; Holt, J. W.
NASA Astrophysics Data System (ADS)
Reflection electron energy-loss spectroscopy (REELS) at low energies is very surface sensitive and can be used to characterize the electronic properties of ultrathin films and surface nanostructures. To extract reliable quantitative information from a REELS experiment it is essential to have accurate theoretical algorithms. In this paper, we have studied the validity of a theoretical method proposed by Yubero and Tougaard [Phys. Rev. B 46, 2486 (1992); Phys. Rev B 53, 9719 (1996)] to determine the dielectric function ? by using an analysis of an effective experimental REELS cross section determined by the Tougaard-Chorkendorff algorithm [Phys Rev B 35, 6570 (1987)]. To this end, REELS experiments with electrons incident normal to the surface were carried out for a wide range of exit angles (35░-74░ to the surface normal) and energies 200, 500, and 1000eV for several materials (Cu, Ag, Au, and Fe). We find that the theory is in very good agreement with experiment for all geometries and energies studied. It is important to note that for a given element, the same ? is used for all geometries and energies and that this ? is determined by the analysis. The fact that the theory applies at energies at least down to 200eV where the inelastic mean free path (?) is ś0.5nm implies that the method can be used to determine the dielectric properties of nanofilms, and the additional fact that the theory can predict the variation with angle suggests that the method might also be used to determine the dielectric properties of nanostructures.
Hajati, Shaaker; Romanyuk, Oleksandr; Zemek, Josef; Tougaard, Sven
Influence of the Static Dynamic Ergodic Divertor on Edge Turbulence Properties in TEXTOR
Systematic measurements on the edge turbulence and turbulent transport have been made by Langmuir probe arrays on TEXTOR under various static Dynamic Ergodic Divertor (DED) configurations. Common features are observed. With the DED, in the ergodic zone the local turbulent flux reverses sign from radially outwards to inwards. The turbulence properties are profoundly modified by energy redistribution in frequency spectra and suppression of large scale eddies. The fluctuation poloidal phase velocity changes direction from electron to ion diamagnetic drift, consistent with the observed reversal of the E{sub r}xB flow. In the laminar region, the turbulence is found to react to an observed reduced flow shear.
Xu, Y.; Weynants, R. R.; Jachmich, S.; Van Schoor, M.; Vergote, M. [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association 'Euratom-Belgian State', Ecole Royale Militaire-Koninklijke Militaire School, B-1000 Brussels (Belgium); Peleman, P. [Department of Applied Physics, Ghent University, B-9000 Ghent (Belgium); Jakubowski, M. W.; Mitri, M.; Reiser, D.; Unterberg, B.; Finken, K. H. [Institute fuer Plasmaphysik, Forschungszentrum Juelich, D-52425 Juelich (Germany)
Static and Dynamic Properties of Trapped Fermionic Tonks-Girardeau Gases
We investigate some exact static and dynamic properties of one-dimensional fermionic Tonks-Girardeau gases in tight de Broglie waveguides with attractive p-wave interactions induced by a Feshbach resonance. A closed form solution for the one-body density matrix for harmonic trapping is analyzed in terms of its natural orbitals, with the surprising result that for odd, but not for even, numbers of fermions the maximally occupied natural orbital coincides with the ground harmonic oscillator orbital and has the maximally allowed fermionic occupancy of unity. The exact dynamics of the trapped gas following turnoff of the p-wave interactions are explored.
M. D. Girardeau; E. M. Wright
Among the high performance engineering materials, fiber-reinforced plastics play an important role. The present work is concerned\\u000a with the comparison of vital static strength properties of fine blanking with conventional drilling on hand lay-up made glass\\u000a fiber-reinforced plastic (GFRP) laminates of four different reinforcement lay-up sequences such as unidirectional [0\\/0]n, angle ply [0?▒?45]ns, quasi-isotropic [0\\/45\\/90]ns, and cross-ply [0\\/90]n. Observation includes
G. Baskaran; S. Gowri; R. Krishnamurthy
We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by Ā?Ā 70% and Ā?Ā 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy. PMID:24876108
Xie, Shawn X; Gao, Fuqiang; Patel, Sunny C; Booske, John H; Hagness, Susan C; Sitharaman, Balaji
Highlights: Black-Right-Pointing-Pointer Rod shaped lanthanum doped bismuth ferrite was obtained. Black-Right-Pointing-Pointer The diameter of the particles were found to be decreasing on doping with lanthanum. Black-Right-Pointing-Pointer Both ferromagnetic and dielectric properties enhanced. Black-Right-Pointing-Pointer A transition due to spin canting is observed near 550 Degree-Sign C. Black-Right-Pointing-Pointer Electron spin resonance study shows the breakage of spin cycloid due to doping. -- Abstract: Cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05, 0.1 and 0.15) were synthesized successfully by hydrothermal method. All samples were found to be rhombohedrally distorted perovskite structure. Diameter of the cylindrical particles reduces from {approx}450 nm for x = 0.0 to {approx}100 nm for x = 0.1 prepared under the same conditions. The Neel temperature as well as the dielectric constant was also found to increase with the increase in lanthanum content. Lanthanum doping also enhanced the magnetic properties. Magnetization measurements above room temperature show a significant increase in magnetization at around 400 Degree-Sign C. Enhanced magnetic properties due to lanthanum doping are caused by the breakage of spin cycloid as observed by electron spin resonance study.
Chaudhuri, A., E-mail: firstname.lastname@example.com [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Mandal, K. [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)] [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)
The effects of various processing conditions, like annealing, poling, mechanical rolling and their combinations, on the dielectric and ferroelectric properties of PVDF [poly(vinylidene fluoride)] were systematically studied in this work. Further, the effect of processing sequence on the structure and properties was investigated. While all the processing conditions adopted here resulted in phase transformation of the ?- to electroactive ?-polymorph in PVDF, the fraction of ?-phase developed was observed to be strongly contingent on the adopted process. The transformation of ? to electroactive ?-polymorph was determined by X-ray diffraction and FTIR. The neat PVDF showed only ?-phase, whereas mechanically rolled samples exhibited the highest ca. 85% ?-phase in PVDF. Both the permittivity and the loss tangent decreased in the samples which had undergone different processing conditions. The polarization-electric field (P-E) loops for all the samples were evaluated. Interestingly, the energy density, estimated from the electrical displacement-electric field (D-E) loops, was observed to be highest for the poled samples which were initially rolled. The results indicate that various processing conditions can influence the dielectric and the ferroelectric properties differently. PMID:24922560
Sharma, Maya; Madras, Giridhar; Bose, Suryasarathi
Effects of annealing on domain-wall contributions to the dielectric properties of PZT thin films
NASA Astrophysics Data System (ADS)
We studied the effects of the annealing process on domain-wall contributions to the dielectric properties of PZT thin films. Two annealing processes, single annealing and layer-by-layer annealing, were used to fabricate PZT thin films. The film thickness was controlled by repeating the spin-coating process. Field-emission scanning electron microscopy and an X-ray diffraction analysis showed the morphological and the structural differences, respectively, between the two films. Based on the analysis of ferroelectric hysteresis loops, we found that PZT thin films fabricated with the single annealing process had larger values of the remanent polarization ( P r ) and the coercive field ( E c ) than PZT thin films fabricated with the layer-by-layer annealing process. The values for the P r and the E c in the two films differed by, at most, 9 ĄC/cm2 and 23 kV/cm. This maximum difference occurred between films that underwent the same number of spin-coating cycles. Using Rayleigh relations, we could explain the differences in ferroelectric properties in terms of domain-wall motion contributions to the dielectric properties.
Cho, Sam Yeon; Kwak, Jin Ho; Yang, Sun A.; Bu, Sang Don; Park, Sungkyun; Lee, Min Ku
Effect of Gd3+ on dielectric and magnetic properties of Y3Fe5O12
NASA Astrophysics Data System (ADS)
The Gd3+ doped Y3-xGdxFe5O12 (x=0.0, 0.05, 0.15, and 0.25) nanopowders were prepared using modified sol-gel route. The structural characterizations such as X-ray diffraction, transmission electron microscopy has been carried out. The nanopowders were sintered at 700 ░C/3 h. The lattice parameters and density of the samples were increased with an increase of Gd3+ concentration. The microstructure was analyzed using atomic force microscopy. The room temperature dielectric (?' and ??) and magnetic (?' and ??) properties were measured in the frequency range 5-50 GHz. with Gd3+ the dielectric properties were enhanced, but there is a decrease in the magnetic properties. The room temperature magnetization studies were carried out up to 1.5 T. the saturation and remnant magnetization were decreased with an increase of gadolinium concentration. These garnets have low permeability, low losses and a broad distribution of FMR line width which makes them a promising material for microwave devices can be used in the high frequency range i.e. up to 50 GHz.
Praveena, K.; Srinath, S.
NASA Astrophysics Data System (ADS)
Two modifications of lead titanate ceramic and the polyetherketoneketone polymer (PEKK) have been used to obtain two polymer/ceramic composites. The piezo-, pyro-, ferroelectric, and dielectric properties were studied. The calcium modified lead titanate/polyetherketoneketone (PTCa/PEKK) composite shows better piezo- and pyro-electric properties than that of the samarium and manganese modified lead titanate/polyetherketoneketone (PSTM/PEKK) composite. Also, a lower dielectric permittivity and remanent polarization values with a higher coercive field are obtained. The results are discussed considering the modifications made in the ceramic phases of each composite. The presented properties for both composites are still substantially lower than those in bulk ceramics.
Pelßiz-Barranco, A.; Marin-Franch, P.
NASA Astrophysics Data System (ADS)
In this work, atmospheric plasma spraying combined with dry-ice blasting have been used to prepare alumina (Al2O3) coatings designed for insulating applications. The microstructural characteristics and dielectric properties of Al2O3 coatings were presented. The electrical insulating properties, i.e., dielectric strength and breakdown voltage, were investigated by dielectric breakdown test using direct current and alternating current. Relationships between dielectric properties and coating characteristics were discussed. The results showed that dry-ice blasting used during atmospheric plasma spray process allowed the production of coatings with better dielectric properties than those prepared without dry-ice blasting. The dielectric properties were correlated with the microstructural characteristics, not with phase composition.
Dong, Shujuan; Song, Bo; Liao, Hanlin; Coddet, Christian
Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises several layers: the epidermis, the dermis, and the subcutaneous fat. Each of these skin layers has a different constitution; however, the previous measurements of their dielectric properties were typically conducted on tissue which included all three layers of the skin. This study presents novel dielectric property data for the epidermis and dermis with in vitro measurement at frequencies ranging from 0.5 GHz to 110 GHz. Measured data was compared with literature values; in particular, the findings were compared with Gabriel's widely used data on skin dielectric properties. The experimental results agreed with the data reported by Gabriel for the dermis of up to 20 GHz, which is the upper limit of the range of frequencies at which Gabriel reported measurements. For frequencies of 20-100 GHz, the experimental results indicated larger values than those extrapolated from Gabriel's data using parametric expansion. For frequencies over 20 GHz, the dielectric properties provided by the parametric model tend toward the experimental results for the epidermis with increasing frequency. PMID:25082800
Sasaki, K; Wake, K; Watanabe, S
NASA Astrophysics Data System (ADS)
Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises several layers: the epidermis, the dermis, and the subcutaneous fat. Each of these skin layers has a different constitution; however, the previous measurements of their dielectric properties were typically conducted on tissue which included all three layers of the skin. This study presents novel dielectric property data for the epidermis and dermis with in vitro measurement at frequencies ranging from 0.5 GHz to 110 GHz. Measured data was compared with literature values; in particular, the findings were compared with GabrielÆs widely used data on skin dielectric properties. The experimental results agreed with the data reported by Gabriel for the dermis of up to 20 GHz, which is the upper limit of the range of frequencies at which Gabriel reported measurements. For frequencies of 20¢100 GHz, the experimental results indicated larger values than those extrapolated from GabrielÆs data using parametric expansion. For frequencies over 20 GHz, the dielectric properties provided by the parametric model tend toward the experimental results for the epidermis with increasing frequency.
Sasaki, K.; Wake, K.; Watanabe, S.
A systematic study has been conducted to examine the thermal stability of layer-by-layer assembled films of perovskite-type nanosheets, (Ca2Nb3O10(-))n (n = 1-10), which exhibit superior dielectric and insulating properties. In-plane and out-of-plane X-ray diffraction data as well as observations by atomic force microscopy and transmission electron microscopy indicated the high thermal robustness of the nanosheet films. In a monolayer film with an extremely small thickness of ?2 nm, the nanosheet was stable up to 800 ░C, the temperature above which segregation into CaNb2O6 and Ca2Nb2O7 began. The critical temperature moderately decreased as the film thickness, or the number of nanosheet layers, increased, and reached 700 ░C for seven- and 10-layer films, which is comparable to the phase transformation temperature for a bulk phase of the protonic layered oxide of HCa2Nb3O10Ę1.5H2O as a precursor of the nanosheet. This thermal stabilization of perovskite-type nanosheets should be associated with restricted nucleation and crystal growth peculiar to such ultrathin 2D bound systems. The stable high-k dielectric response (?r = 210) and highly insulating nature (J < 10(-7) A cm(-2)) remained substantially unchanged even after the nanosheet film was annealed up to 600 ░C. This study demonstrates the high thermal stability of 2D perovskite-type niobate nanosheets in terms of structure and dielectric properties, which suggests promising potential for future high-k devices operable over a wide temperature range. PMID:24797417
Li, Bao-Wen; Osada, Minoru; Ebina, Yasuo; Akatsuka, Kosho; Fukuda, Katsutoshi; Sasaki, Takayoshi
Dielectric and transport properties of thin films precipitated from sols with silicon nanoparticles
Dielectric properties of thin films precipitated on solid substrates from colloidal solutions containing silicon nanoparticles (average diameter is 10 nm) are studied by optical ellipsometry and impedance-spectroscopy. In the optical region, the values of real {epsilon} Prime and imaginary {epsilon} Double-Prime components of the complex permittivity {epsilon} vary within 2.1-1.1 and 0.25-0.75, respectively. These values are significantly lower than those of crystalline silicon. Using numerical simulation within the Bruggeman effective medium approximation, we show that the experimental {epsilon} Prime and {epsilon} Double-Prime spectra can be explained with good accuracy, assuming that the silicon film is a porous medium consisting of silicon monoxide (SiO) and air voids at a void ratio of 0.5. Such behavior of films is mainly caused by the effect of outer shells of silicon nanoparticles interacting with atmospheric oxygen on their dielectric properties. In the frequency range of 10-10{sup 6} Hz, the experimentally measured {epsilon} Prime and {epsilon} Double-Prime spectra of thin nanoscale silicon films are well approximated by the semi-empirical Cole-Cole dielectric dispersion law with the term related to free electric charges. The experimentally determined power-law frequency dependence of the ac conductivity means that the electrical transport in films is controlled by electric charge hopping through localized states in the unordered medium of outer shells of silicon nanoparticles composing films. It is found that the film conductivity at frequencies of {<=}2 Multiplication-Sign 10{sup 2} Hz is controlled by proton transport through Si-OH groups on the silicon nanoparticle surface.
Kononov, N. N., E-mail: firstname.lastname@example.com [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Dorofeev, S. G. [Moscow State University, Faculty of Chemistry (Russian Federation); Ishchenko, A. A. [Lomonosov State Academy of Fine Chemical Technology (Russian Federation); Mironov, R. A.; Plotnichenko, V. G.; Dianov, E. M. [Russian Academy of Sciences, Fiber-Optics Research Center, Prokhorov General Physics Institute (Russian Federation)
Correlations in the properties of static and rapidly rotating compact stars
Correlations in the properties of the static compact stars (CSs) and the ones rotating with the highest observed frequency of 1122 Hz are studied using a large set of equations of state (EOSs). These EOSs span various approaches and their chemical composition varies from the nucleons to hyperons and quarks in {beta}-equilibrium. It is found that the properties of static CS, like the maximum gravitational mass M{sub max}{sup stat} and radius R{sub 1.4}{sup stat} corresponding to the canonical mass and supramassive or nonsupramassive nature of the CS rotating at 1122 Hz are strongly correlated. In particular, only those EOSs yield the CS rotating at 1122 Hz to be nonsupramassive for which ((M{sub max}{sup stat}/M{sub {center_dot}})){sup 1/2}((10 km/R{sub 1.4}{sup stat})){sup 3/2} is greater than unity. A suitable parametric form which can be used to split the M{sub max}{sup stat}-R{sub 1.4}{sup stat} plane into the regions of different supramassive nature of the CS rotating at 1122 Hz is presented. Currently measured maximum gravitational mass 1.76M{sub {center_dot}} of PSR J0437-4715 suggests that the CS rotating at 1122 Hz can be nonsupramassive provided R{sub 1.4}{sup stat}{<=}12.4 km.
Agrawal, B. K.; Kumar, Raj; Dhiman, Shashi K. [Saha Institute of Nuclear Physics, Kolkata-700064 (India); Department of Physics, Himachal Pradesh University, Shimla-171005 (India)
NASA Astrophysics Data System (ADS)
SrTiO3 (STO) thin films were grown simultaneously via the metal organic chemical vapor deposition (MOCVD) technique on two different substrates: platinized sapphire and platinized TiO2/SiO2/Si. The thin films were analyzed for stoichiometry, crystallinity, surface roughness, and average grain size. Dielectric properties of the thin films such as dielectric constant, loss, and leakage current characteristics were measured and compared. We demonstrate that the MOCVD technique is an appropriate method for fabrication of STO thin films with excellent structural, microstructural, dielectric, and insulation properties. Comparative analysis of the films yielded an unexpected result that the thin film with a higher mismatch in thermal expansion coefficient between the substrate (Si) and the deposited STO film yielded a higher dielectric constant with respect to that of STO/sapphire. The dielectric loss for both films were similar (tan ? = 0.005 at 100 kHz), however, the leakage current for the film with a higher dielectric constant was three orders of magnitude higher. An explanation of these results is presented and discussed.
Shreiber, D.; Cole, M. W.; Enriquez, E.; Hirsch, S. G.; Ngo, E.; Hubbard, C.; Ivill, M.; Chen, Chonglin
Evolving Density and Static Mechanical Properties in Plutonium from Self-Irradiation
Plutonium, because of its self-irradiation by alpha decay, ages by means of lattice damage and helium in-growth. These integrated aging effects result in microstructural and physical property changes. Because these effects would normally require decades to measure, studies are underway to assess the effects of extended aging on the physical properties of plutonium alloys by incorporating roughly 7.5 weight % of highly specific activity isotope {sup 238}Pu into the {sup 239}Pu metal to accelerate the aging process. This paper presents updated results of self-irradiation effects on {sup 238}Pu-enriched alloys measured by immersion density, dilatometry, and tensile tests. After nearly 90 equivalent years of aging, both the immersion density and dilatometry show that the enriched alloys continue to decreased in density by {approx}0.002% per year, without void swelling. Quasi-static tensile measurements show that the aging process increases the strength of plutonium alloys.
Chung, B W; Thompson, S R; Lema, K E; Hiromoto, D S; Ebbinghaus, B B
Structural and dielectric properties of LaFe1-xZnxO3(0?x?0.3)
NASA Astrophysics Data System (ADS)
We have studied the structural and dielectric properties of nano-crystalline LaFe1-xZnxO3(0?x?0.3) perovskite samples. The samples were synthesized by sol-gel auto-combustion technique and show the orthorhombic crystal structure at room temperature. Dielectric responses of studied system have been analyzed in the light of "universal dielectric response (UDR)"h model. The value of dielectric constant (?') is found to be hugely enhanced with Zn substitution. To verify the UDR behaviour, the log(?) versus log(??') graphs have been plotted. We have found the best linear fit for the host (LaFeO3) sample in the whole frequency range and for the other samples the linear behaviour is observed at low frequency regions only.
Bhat, Irshad; Husain, Shahid; Khan, Wasi
NASA Astrophysics Data System (ADS)
Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.
Olariu, C. S.; Padurariu, L.; Stanculescu, R.; Baldisserri, C.; Galassi, C.; Mitoseriu, L.
NASA Astrophysics Data System (ADS)
Usually, the trapping phenomenon in insulating materials is studied by injecting charges using a Scanning Electron Microscope. In this work, we use the dielectric spectroscopy technique for showing a correlation between the dielectric properties and the trapping-charging ability of insulating materials. The evolution of the complex permittivity (real and imaginary parts) as a function of frequency and temperature reveals different types of relaxation according to the trapping ability of the material. We found that the space charge relaxation at low frequencies affects the real part of the complex permittivity ? ' and the dissipation factor Tan(?). We prove that the evolution of the imaginary part of the complex permittivity against temperature ? ? = f ( T ) reflects the phenomenon of charge trapping and detrapping as well as trapped charge evolution Qp(T). We also use the electric modulus formalism to better identify the space charge relaxation. The investigation of trapping or conductive nature of insulating materials was mainly made by studying the activation energy and conductivity. The conduction and trapping parameters are determined using the Correlated Barrier Hopping (CBH) model in order to confirm the relation between electrical properties and charge trapping ability.
Mekni, Omar; Arifa, Hakim; Askri, Besma; Raouadi, Khaled; Damamme, Gilles; Yangui, Bķchir
NASA Astrophysics Data System (ADS)
In this paper, microorganism cells (Spirulina platens) were used as forming templates for the fabrication of the helical functional particles by electroless silver plating process. The morphologies and ingredients of the coated Spirulina cells were analyzed with scanning electron microscopy and energy dispersive spectrometer. The crystal structures were characterized by employing the X-ray diffraction. The electrical resistivity and dielectric properties of samples containing different volume faction of sliver-coated Spirulina cells were measured and investigated by four-probe meter and vector network analyzer. The results showed that the Spirulina cells were successfully coated with a uniform silver coating and their initial helical shapes were perfectly kept. The electrical resistivity and dielectric properties of the samples had a strong dependence on the volume content of sliver-coated Spirulina cells and the samples could achieve a low percolation value owing to high aspect ratio and preferable helical shape of Spirulina cells. Furthermore, the conductive mechanism was analyzed with the classic percolation theory, and the values of ? and t were obtained.
Cai, Jun; Lan, Mingming; Zhang, Deyuan; Zhang, Wenqiang
Dielectric properties of hydrogen-incorporated chemical vapor deposited diamond thin films
NASA Astrophysics Data System (ADS)
Diamond thin films with a broad range of microstructures from a ultrananocrystalline diamond (UNCD) form developed at Argonne National Laboratory to a microcrystalline diamond (MCD) form have been grown with different hydrogen percentages in the Ar /CH4 gas mixture used in the microwave plasma enhanced chemical vapor deposition (CVD) process. The dielectric properties of the CVD diamond thin films have been studied using impedance and dc measurements on metal-diamond-metal test structures. Close correlations have been observed between the hydrogen content in the bulk of the diamond films, measured by elastic recoil detection (ERD), and their electrical conductivity and capacitance-frequency (C-f) behaviors. Addition of hydrogen gas in the Ar /CH4 gas mixture used to grow the diamond films appears to have two main effects depending on the film microstructure, namely, (a) in the UNCD films, hydrogen incorporates into the atomically abrupt grain boundaries satisfying sp2 carbon dangling bonds, resulting in increased resistivity, and (b) in MCD, atomic hydrogen produced in the plasma etches preferentially the graphitic phase codepositing with the diamond phase, resulting in the statistical survival and growth of large diamond grains and dominance of the diamond phase, and thus having significant impact on the dielectric properties of these films.
Liu, Chao; Xiao, Xingcheng; Wang, Jian; Shi, Bing; Adiga, Vivekananda P.; Carpick, Robert W.; Carlisle, John A.; Auciello, Orlando
Measurement of the dielectric properties of dispersive materials over a wide frequency range.
The propagation of electromagnetic waves through dispersive media forms the basis for a wide variety of applications. Rapid advances in materials have produced new products with tailored responses across frequency bands. Many of these new materials, such as radar absorbing material and photonic crystals, are dispersive in nature. This, in turn, has opened up the possibility for the exploitation of these dispersive dielectric properties for a variety of applications. Thus, it is desirable to know the electromagnetic properties of both man-made and natural materials across a wide frequency range. With the advent of transient pulsers with sub-nanosecond risetimes and rates of voltage rise approaching 10**16 V/s, the frequencies of interest in the transient response extend to approximately the 2 GHz range. Although a network analyzer can provide either frequency- or time-domain data (by inverse transform), common TEM cells are only rated to 0.5 to 1.5 GHz--significantly below the maximum frequency of interest. To extend the frequency range to include 2 GHz, a TEM cell was characterized and a deembedding algorithm was applied to account, in part, for the limitations of the cell. The de-embedding technique is described along with such measurement issues such as clear time and sneak around. Measurements of complex permittivity of common drinking water are shown. This frequency extension will lead to more expansive testing of dielectric materials of interest.
Molina, Luis Leroy; Salazar, Robert Austin; Bacon, Larry Donald; Lehr, Jane Marie
Breast imaging via microwave tomography involves estimating the distribution of dielectric properties within the patient's breast on a discrete mesh. The number of unknowns in the discrete mesh can be very large for three-dimensional imaging, and this results in computational challenges. We propose a new approach where the discrete mesh is replaced with a relatively small number of smooth basis functions. The dimension of the tomography problem is reduced by estimating the coefficients of the basis functions instead of the dielectric properties at each element in the discrete mesh. The basis functions are constructed using knowledge of the location of the breast surface. The number of functions used in the basis can be varied to balance resolution and computational complexity. The reduced dimension of the inverse problem enables application of a computationally efficient, multiple-frequency inverse scattering algorithm in 3-D. The efficacy of the proposed approach is verified using two 3-D anatomically realistic numerical breast phantoms. It is shown for the case of single-frequency microwave tomography that the imaging accuracy is comparable to that obtained when the original discrete mesh is used, despite the reduction of the dimension of the inverse problem. Results are also shown for a multiple-frequency algorithm where it is computationally challenging to use the original discrete mesh. PMID:19211350
Winters, David W.; Shea, Jacob D.; Kosmas, Panagiotis; Van Veen, Barry D.; Hagness, Susan C.
NASA Astrophysics Data System (ADS)
The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675░C were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to the ?-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.
Su, Xin; Xu, Guang-ming; Jiang, Jiu-wen
Effect of medium dielectric constant on the physical properties of single-walled carbon nanotubes
NASA Astrophysics Data System (ADS)
The photophysical properties of semiconducting single walled carbon nanotubes (SWNTs) in different environments are analyzed by steady-state and time-resolved photoluminescence (PL) spectroscopy. The PL emission of SWNTs shows a red shift with the increase of the dielectric constant of the environments. The solvatochromic shift depends on the structural properties of the nanotubes and reaches almost 100 milli-electron volts in the case of (7, 5) tubes. These experimental results allow deriving a relationship between the PL shift and the structure of SWNTs. Moreover, the dynamics of 'bright' excitons in semiconducting SWNTs and the effect of the medium on the decay of the excitons are discussed by using time-resolved spectroscopy.
Gao, J.; Gomulya, W.; Loi, M. A.
Effects of dopants on the piezoelectric and dielectric properties of Sm-modified PbTiO 3 ceramics
Doping effects on the piezoelectric and dielectric properties of PbTiO3-based ceramics have been investigated. Sm-modified PbTiO3 ceramics, doped with BiFeO3 (BF) and Ba(Cu0.5W0.5)O3(BCW), were prepared by conventional mixed-oxide methods with sintering temperatures of 1000¢1250░C. In this paper, we successfully show that these additives were helpful in lowering the sintering temperature while still obtaining similar dielectric and piezoelectric properties. The preferred
Sheng-Yuan Chu; Chia-Hsin Chen
NASA Astrophysics Data System (ADS)
Piezoelectric properties of KNbO3 crystals were investigated as a function of the crystallographic direction, such as [110]c of polar direction and [001]c of engineered domain direction. It was confirmed that the sample preparation process induced mechanical damage into the crystals. Thus, the optimum conditions for the mechanical processing of KNbO3 crystals were investigated, and the stressed surface layers of KNbO3 crystals were successfully removed by the chemical etching. It was revealed that the removal of the stressed surface layers was very effective to achieve high mechanical quality factor (Qm). After the treatment, KNbO3 crystals were poled by the 2-step poling method. Using a polarizing microscope, the domain configuration of the poled KNbO3 crystals was observed and was confirmed that the crystal was almost in single-domain state. Using this poled KNbO3 single-domain crystals, the piezoelectric properties with k31 modes were measured using a conventional resonance method. As a result, the [110]c poled KNbO3 crystals exhibited an electromechanical coupling factor (k31) of almost 47 %, the piezoelectric constant (d31) of almost 22 pC/N, the dielectric constant (e33) of almost 44 and Qm over 4,000. These values are extremely higher compared to previous reports on KNbO3 crystals, except for e 33. This result revealed that the KNbO3 crystals are piezoelectric with low dielectric and high electromechanical coupling properties, which makes KNbO3 crystal one of the promising materials for sensor application. Moreover, the piezoelectric properties with k32, k33, k15 and k24 modes were also investigated. Finally, the effect of the engineered domain is discussed.
Wada, Satoshi; Muraoka, K.; Kakemoto, H.; Kumagai, H.; Tsurumi, T.; Science, Graduate School Of; Engineering Collaboration
The dependence of lead-salt nanocrystal properties on morphology and dielectric environment
NASA Astrophysics Data System (ADS)
The IV-VI semiconductors, and specifically the lead-salts (PbS, PbSe, and PbTe), are a natural choice for nanocrystal science. In nanocrystals, because of their narrow band gap, small effective masses, and large dielectric constants, they offer a unique combination of both strong confinement and strong dielectric contrast with their environment. Studying how these two effects modify optical and electrical properties of nanocrystals will be the topic of this dissertation. We begin with a summary of the synthesis of high-quality PbS and PbSe nanocrystals. Special care is taken to explain the chemical procedures in detail to an audience not expected to have significant prior chemistry knowledge. The synthesized nanocrystals have bright and tunable emission that spans the edge of the visible to the near-IR spectrum (700--1800 nm), and they are capped with organic ligands making them easily adaptable to different substrates or hosts. This combination of high optical quality and flexible device engineering make them extremely desirable for application. Moving beyond single-material nanocrystals, we next explore nanocrystal heterostructures, specifically materials with a spherical core of one semiconductor and a shell of another. Core-shell structures are commonly used in nanocrystals as a method to separate the core material, where the electrons and holes are expected to stay, from interfering effects at the surface. This typically results in improvements in stability and fluorescence quantum efficiency. To that end, we develop a model to explain how confinement plays out across abrupt changes in material, focusing on the optical and electrical properties of recently synthesized PbSe/PbS core-shell quantum dots. We show that for typical sizes of these nanocrystals, a novel type of nanocrystal heterostructure is created, where electrons and holes extend uniformly across the abrupt material boundary, and the shell does not act as a protecting layer. For very large sizes not yet achievable, we expect that the electron and hole will separate in different layers, with potentially measurable effects. Comparisons are made to optical and electrical measurements on these structures, showing good agreement. Next, we explore how shape can impact nanocrystal properties, on top of their intrinsic size or material dependence. By looking at cylindrically shaped nanocrystals, called "nanorods," with aspect ratios ? 10, we explore how having a slightly extended dimension can impact nanocrystal properties. A model is developed to explain their electronic structure, with surprising results. Foremost is that along the extended dimension, electrons and holes are strongly electrically bound, not with each other directly, but with their image charges in the outer host dielectric material. Nevertheless, the energy spectra of the excitons remains nearly host-independent, with the effects of this strong binding instead seen in a redistribution of transition oscillator strength. To test the model, we develop a novel synthesis of high quality PbSe nanorods, and find good agreement with measured absorption spectra. Finally, we present a study on the transfer of charge into and out of a nanocrystal. By modeling the charge transfer process within a modified Marcus Theory, we isolate the relevant parameters that can be used to control the rate of transfer. Primary among these are the values of the quantum dot energy levels, and the electrostatic charging energy of the acceptor. We vary the former by changing the quantum dot size, and the latter by varying the host dielectric constant. To test the model, we chemically bind a small molecular acceptor molecule to the surface of PbS nanocrystals and use transient fluorescence to measure the rate of charge transfer. Both the dependence of the rate on quantum dot size and host dielectric constant show good agreement with the model.
Bartnik, Adam Christopher
The present work reports for the first time quantitative structure-property relationships, derived at the benchmark CCSD(T)/cc-PVTZ level of theory that estimate the static longitudinal, transverse, and molecular polarizability in polyynes (C2nH2), as a function of their length (L). In the case of independent electron models, regardless of the form of the nuclei potential that the electrons experience, the polarizability increases strongly with system size, scaling as L(4). In contrast, the static longitudinal polarizability in polyynes have a considerably weaker length-dependence (L(1.64)). This is shown to predominantly arise from electron-electron repulsion rather than electron correlation by a systematic study of the polarizability length dependence in several simple quantum mechanical systems (e.g., particle-in-box, simple harmonic oscillator) and other molecular systems (e.g., H2, H2(+), polyynes). Decrease of the electron-electron repulsion term is suggested to be the key factor in enhancing nonlinear polarizability characteristics of linear oligomeric and polymeric materials. PMID:18528978
Zeinalipour-Yazdi, Constantinos D; Pullman, David P
The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we
Mariya Lazebnik; Dijana Popovic; Leah McCartney; Cynthia B. Watkins; Mary J. Lindstrom; Josephine Harter; Sarah Sewall; Travis Ogilvie; Anthony Magliocco; Tara M. Breslin; Walley Temple; Daphne Mew; John H. Booske; Michal Okoniewski; Susan C. Hagness
Solution-deposited GdCeO{sub x} thin films: Microstructure, band structure, and dielectric property
Highlights: ? Microstructural and electrical properties of sol¢gel-deposited GdCeO{sub x} thin films with different mixing ratios. ? Ce incorporation enhanced crystallization and refractive index, reduced hysteresis, and increased dielectric constant. ? Bandgap gradually decreased with increasing Ce, which was primarily affected by VBO reduction. -- Abstract: The microstructural and electrical properties of solution-deposited GdCeO{sub x} dielectric thin films with different mixing ratios were studied. The Ce incorporation enhanced the degree of crystallization and the refractive index of the Gd{sub 2}O{sub 3} film, reduced the hysteresis and increased the dielectric constant. According to reflective electron energy loss spectroscopy and X-ray photoelectron spectroscopy analyses, the bandgap of the GdCeO{sub x} film gradually decreased with increasing Ce/(Gd + Ce) atomic ratio, which was primarily affected by the reduction of the valence band offset.
Lee, Myung Soo [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)] [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Sang Han; Cho, Mann-Ho [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)] [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyoungsub, E-mail: email@example.com [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)] [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
NASA Astrophysics Data System (ADS)
Chrysanthemum-like ZnO nanowire clusters with different Sb-doping concentrations were prepared using a hydrothermal process. The microstructures, morphologies, and dielectric properties of the as-prepared products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission environment scanning electron microscope (FEESEM), and microwave vector network analyzer respectively. The results indicate that the as-prepared products are Sb-doped ZnO single crystallines with a hexagonal wurtzite structure, the flower bud saturation degree Fd is obviously different from that of the pure ZnO nanowire clusters, the good dielectric loss property is found in Sb-doped ZnO products with low density, and the dielectric loss tangent tan?e increases with the increase of the Sb-doping concentration in a certain concentration range.
Yan, Jun-Feng; You, Tian-Gui; Zhang, Zhi-Yong; Tian, Jiang-Xiao; Yun, Jiang-Ni; Zhao, Wu
Dielectric property of NiTiO{sub 3} doped substituted ortho-chloropolyaniline composites
Ortho-chloropolyaniline (OCP)-NiTiO{sub 3} composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO{sub 3.} Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO{sub 3} particles. Surface morphology of OCP and OCP-NiTiO{sub 3} composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO{sub 3} composites have been investigated in the frequency range of 50 Hz ¢ 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO{sub 3} particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.
Lakshmi, Mohana; Faisal, Muhammad [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India)] [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India); Roy, Aashish S. [Department of Materials Science, Gulbarga University, Gulbarga-585106, Karnataka (India)] [Department of Materials Science, Gulbarga University, Gulbarga-585106, Karnataka (India); Khasim, Syed, E-mail: email@example.com [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India) [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India); Department of Physics, University of Tabuk-71491 (Saudi Arabia); Sajjan, K. C. [Department of Physics, Veerashaiva College, Bellary - 583 104, Karnataka (India)] [Department of Physics, Veerashaiva College, Bellary - 583 104, Karnataka (India); Revanasiddappa, M. [Department of Chemistry, PES Institute of Technology, BSC, Bangalore - 560100 (India)] [Department of Chemistry, PES Institute of Technology, BSC, Bangalore - 560100 (India)
Revisiting the low-temperature dielectric properties of ZnO
NASA Astrophysics Data System (ADS)
Electric modulus spectroscopy and impedance analysis were used to investigate the low-temperature (ś100-333 K) dielectric properties of ZnO crystals. Two relaxations were observed. The low-temperature relaxation (R1) features a thermally activated behavior resulting from the bulk response. Our results convincingly demonstrate that this relaxation is a polaronic relaxation. The relaxing species for R1 are localized holes created by zinc vacancies instead of the commonly agreed oxygen vacancies. The high-temperature relaxation (R2) is a Maxwell-Wagner relaxation due to skin-layer effect as it can be eliminated by grinding off the sample surface. The inhomogeneous distribution of zinc interstitials leads to the formation of the skin layer. Interestingly, an abnormal dielectric behavior contrary to the thermally activated behavior was found for the R2 relaxation. This abnormal behavior was confirmed to be related to the positive temperature coefficient of resistance due to the metal-insulator transition occurring within the skin layer.
Wang, Chunchang; Liu, Lina; Li, Qiuju; Huang, Shouguo; Zhang, Jian; Zheng, Jun; Cheng, Chao
Dielectric property of NiTiO3 doped substituted ortho-chloropolyaniline composites
NASA Astrophysics Data System (ADS)
Ortho-chloropolyaniline (OCP)-NiTiO3 composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO3. Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO3 particles. Surface morphology of OCP and OCP-NiTiO3 composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO3 composites have been investigated in the frequency range of 50 Hz - 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO3 particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.
Lakshmi, Mohana; Roy, Aashish S.; Khasim, Syed; Faisal, Muhammad; Sajjan, K. C.; Revanasiddappa, M.
Influence of SBN70 concentration in PVDF on dielectric and pyroelectric properties of nanocomposites
NASA Astrophysics Data System (ADS)
Strontium barium niobate Sr0.7Ba0.3Nb2O6 (SBN70) ceramic nanopowder was dispersed in a poly(vinylidene fluoride) (PVDF) matrix providing a composite with 0-3 connectivity. The SBN70-PVDF composites samples were obtained from ceramic and polymer powders by hot-pressing method. The SBN70 ceramic was prepared by a sol-gel method. The composite surface images were obtained by AFM tapping mode (NT-NDT Solver P47). The dielectric response of the composites was studied in the frequency range 100 Hz - 1 MHz and the temperature range 100 - 430 K. The dielectric properties of the composites display features originated from the PVDF polymer modified by those of SBN70 ceramics. The resulting pyroelectric currents were measured using a Keithley 6517 A electrometer and were used to calculate the pyroelectric coefficient p. The p of poled composites increases from ~24 ?C/m2ĘK in pure PVDF to ~40 ?C/m2ĘK in the composites of ? = 0.2 at room temperature.
Olszowy, M.; Nogas-?wikiel, E.; ?wikiel, K.
NASA Astrophysics Data System (ADS)
The electrical transport properties and dielectric relaxation of Au/zinc phthalocyanine, ZnPC/Au devices have been investigated. The DC thermal activation energy at temperature region 400-500 K is 0.78 eV. The dominant conduction mechanisms in the device are ohmic conduction below 1 V and space charge limited conduction dominated by exponential trap distribution in potentials >1 V. Some parameters, such as concentration of thermally generated holes in valence band, the trap concentration per unit energy range at the valence band edge, the total concentration of traps and the temperature parameter characterizing the exponential trap distribution and their relation with temperatures have been determined. The AC electrical conductivity, ?ac, as a function of temperature and frequency has been investigated. It showed a frequency and temperature dependence of AC conductivity for films in the temperature range 300-400 K. The films conductivity in the temperature range 400-435 K increased with increasing temperature and it shows no response for frequency change. The dominant conduction mechanism is the correlated barrier hopping. The temperature and frequency dependence of real and imaginary dielectric constants and loss tangent were investigated.
Zeyada, H. M.; El-Nahass, M. M.
Structure, dielectric, and magnetic properties of Sr2TiMnO6 ceramics
NASA Astrophysics Data System (ADS)
Sr2TiMnO6, a double perovskite associated with high degree of B-site cation disorder was investigated in detail for its structural, magnetic, and dielectric properties. Though x-ray powder diffraction analysis confirms its cubic structure, first order Raman scattering and infrared reflectivity spectra indicate a breaking of the local cubic symmetry. The magnetization study reveals an anomaly at 14 K owing to a ferrimagnetic/canted antiferromagneticlike ordering arising from local Mn-O-Mn clusters. Saturated M-H hysteresis loops obtained at 5 K also reflect the weak ferromagnetic exchange interactions present in the system and an approximate estimation of Mn3+/Mn4+ was done using the magnetization data for the samples sintered at different temperatures. The conductivity and dielectric behavior of this system has been investigated in a broad temperature range of 10 to 300 K. Intrinsic permittivity was obtained only below 100 K whereas giant permittivity due to conductivity and Maxwell-Wagner polarization was observed at higher temperatures. X-ray photoemission studies further confirmed the presence of mixed oxidation states of Mn and the valence band spectra analysis was carried out in detail.
Meher, K. R. S. Preethi; Savinov, M.; Kamba, S.; Goian, V.; Varma, K. B. R.
NASA Astrophysics Data System (ADS)
Carboxymethyl cellulose (CMC)/Polyvinyl alcohol (PVA) blend films were prepared by solution casting method. Then, these films were irradiated with ?-rays from a Co-60 source at doses over the range 0-70 kGy to investigate the modifications induced in the optical and dielectric properties. The dielectric constant (??) was measured in the temperature range 303-408 K and in the frequency range 10 kHz-1 MHz. The indirect optical band gap was found to increase within the dose range 0-10 kGy, and to decrease at the higher doses. The refractive index values, however, showed a reversed behavior. The highest transmittance percentage was obtained at 10 kGy dose. According to the frequency and temperature dependence of ??, ?- relaxation peaks were observed in all samples and assigned to the micro-Brownian motion of the blend chains. The values of ?? showed a decrease in the dose range 0-10 kGy and an increase in the dose range 10-70 kGy. The ac conductivity ?ac (T) showed an Arrhenius type behavior separated into two distinct regions. The results of the present system are compared with those of similar materials.
El Sayed, A. M.
Transmission-Line Properties of Parallel Strips Separated by a Dielectric Sheet
A transmission line is made of a symmetrical pair of strip conductors, or a single strip and a ground plane, on opposite faces of a sheet of dielectric material. There is computed, to a close approximation, the relations among the dielectric constant of the sheet, the effective dielectric constant of the sheet and the empty space, the shape ratio, and
H. A. Wheeler
microscope. Dielectric constants of the NLC's were determined by a bridge method for layers of 160 mp. C. bridge at 1000 Hz ; the accuracy was estimated to be f 5 "/,. The dielectric constants were Compound Transition index temperatures (OC) Dielectric constants Melting Clearing Tem
Boyer, Edmond
Study of Some Dielectric Properties of Suspensions of Magnesium Particles in Mineral Oil
NASA Technical Reports Server (NTRS)
The variation of dielectric constant has been measured as a function of the concentration of magnesium particles; the shape, size, and degree of oxidation of the particles; the temperature; and the frequency of oscillation. The variation of dielectric constant and settling rate was investigated as a function of time. Also investigated were the effects of particle concentration, shape and time on dielectric losses.
Altshuller, Aubrey P
In this work we apply low-loss electron energy loss spectroscopy (EELS) to probe the structural and electronic properties of single silicon nanocrystals (NCs) embedded in three different dielectric matrices (SiO2, SiC and Si3N4). A monochromated and aberration corrected transmission electron microscope has been operated at 80 kV to avoid sample damage and to reduce the impact of radiative losses. We present a novel approach to disentangle the electronic features corresponding to pure Si-NCs from the surrounding dielectric material contribution through an appropriate computational treatment of hyperspectral datasets. First, the different material phases have been identified by measuring the plasmon energy. Due to the overlapping of Si-NCs and dielectric matrix information, the variable shape and position of mixed plasmonic features increases the difficulty of non-linear fitting methods to identify and separate the components in the EELS signal. We have managed to solve this problem for silicon oxide and nitride systems by applying multivariate analysis methods that can factorize the hyperspectral datacubes in selected regions. By doing so, the EELS spectra are re-expressed as a function of abundance of Si-NC-like and dielectric-like factors. EELS contributions from the embedded nanoparticles as well as their dielectric surroundings are thus studied in a new light, and compared with the dielectric material and crystalline silicon from the substrate. Electronic properties such as band gaps and plasmon shifts can be obtained by a straightforward examination. Finally, we have calculated the complex dielectric functions and the related electron effective mass and density of valence electrons. PMID:25363292
Eljarrat, Alberto; L¾pez-Conesa, LluĒs; L¾pez-Vidrier, Julian; Hernßndez, Sergi; Garrido, Blas; Magķn, Cķsar; Peir¾, Francesca; Estradķ, S"nia
NASA Astrophysics Data System (ADS)
The dependences of density and static dielectric permeability of water solutions of polyethylene glycol-600 on temperature and polyglycol concentration are studied. It is found that the maximum in the dependences of dielectric permeability on solvent composition is due to intermolecular interactions between water and polyglycol, resulting in the formation of oxonium compounds. The solubility of cesium perchlorate CsClO4 in a water-polyethylene glycol-600 system is investigated using radioactive indicators with 137Cs isotopes over the range of concentrations of mixed solvents at temperatures ranging from 278.15 to 318.15 K. Thermodynamic characteristics of CsClO4 dissolution in mixed solvents are also calculated and analyzed.
Yukhno, G. D.; Krasnoperova, A. P.
The static and dynamical properties of heavy water have been studied at ambient conditions with extensive Car-Parrinello molecular-dynamics simulations in the canonical ensemble, with temperatures ranging between 325 K and 400 K. Density-functional theory, paired with a modern exchange-correlation functional (PBE), provides an excellent agreement for the structural properties and binding energy of the water monomer and dimer. On the other hand, the structural and dynamical properties of the bulk liquid show a clear enhancement of the local structure compared to experimental results; a distinctive transition to liquid-like diffusion occurs in the simulations only at the elevated temperature of 400 K. Extensive runs of up to 50 picoseconds are needed to obtain well-converged thermal averages; the use of ultrasoft or norm-conserving pseudopotentials and the larger plane-wave sets associated with the latter choice had, as expected, only negligible effects on the final result. Finite-size effects in the liquid state are found to be mostly negligible for systems as small as 32 molecules per unit cell.
P. H-L. Sit; Nicola Marzari
NASA Astrophysics Data System (ADS)
A material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties was produced using multi-wall carbon nanotubes (MWCNTs) wrapped with poly(ether sulphone) (PES) dispersed in a poly(ether ether ketone) (PEEK) matrix. The material was fabricated using melt-blending, and MWCNT/PEEK composites show different degrees of improvement in the measured dielectric, mechanical, and thermal properties as compared to pure PEEK. This is attributed to the high conductivity of MWCNTs, the effect of wrapping MWCNTs with PES, the good dispersion of the wrapped MWCNTs in PEEK, and the strong interfacial adhesion between the wrapped MWCNTs and the PEEK.
Zhang, Shuling; Wang, Hongsong; Wang, Guibin; Jiang, Zhenhua
Although dielectrophoresis (DEP) has great potential for addressing clinical cell isolation problems based on cell dielectric differences, a biological basis for predicting the DEP behavior of cells has been lacking. Here, the dielectric properties of the NCI-60 panel of tumor cell types have been measured by dielectrophoretic (DEP) field-flow fractionation, correlated with the exterior morphologies of the cells during growth, and compared with the dielectric and morphological characteristics of the subpopulations of peripheral blood. In agreement with earlier findings, cell total capacitance varied with both cell size and plasma membrane folding and the dielectric properties of the NCI-60 cell types in suspension reflected the plasma membrane area and volume of the cells at their growth sites. Therefore, the behavior of cells in DEP-based manipulations is largely determined by their exterior morphological characteristics prior to release into suspension. As a consequence, DEP is able to discriminate between cells of similar size having different morphological origins, offering a significant advantage over size-based filtering for isolating circulating tumor cells, for example. The findings provide a framework for anticipating cell dielectric behavior on the basis of structure-function relationships and suggest that DEP should be widely applicable as a surface marker-independent method for sorting cells. PMID:23172680
Gascoyne, Peter R. C.; Shim, Sangjo; Noshari, Jamileh; Becker, Frederick F.; Stemke-Hale, Katherine
Inkjet-printing of nonsintered alumina-resin hybrid films and their dielectric properties
NASA Astrophysics Data System (ADS)
We used the inkjet printing method to fabricate alumina-resin hybrid films without a high temperature sintering process. The dielectric properties of the alumina-resin hybrid films were studied in order to assess if the alumina-resin hybrid films are applicable to the electronic package substrates. Various numerical models were introduced to understand the relative permittivity of the alumina-resin hybrid films. Q-values of the alumina-resin hybrid films are also measured and compared to the commercially available substrate materials. The impact of microvoids on the Q-value of the inkjet-printed alumina-resin hybrid films was also studied. The microstructures of the inkjet-printed hybrid materials were investigated in order to confirm if the microvoids in the films were filled with the resin.
Hwang, Myung-sung; Kim, Jihoon; Kim, Hyo-tae; Yoon, Youngjoon; Hyun, Sangil; Kim, Jonghee; Lee, Sung-nam; Moon, Jooho
Temperature dependent transport and dielectric properties of cadmium titanate nanofiber mats
NASA Astrophysics Data System (ADS)
We investigate electrical and dielectric properties of cadmium titanate (CdTiO3) nanofiber mats prepared by electrospinning. The nanofibers were polycrystalline having diameter ś50 nm-200 nm, average length ś100 ?m and crystallite size ś25 nm. Alternating current impedance measurements were carried out from 318 K - 498 K. The frequency of ac signal was varied from 2 - 105 Hz. The complex impedance plots revealed two depressed semicircular arcs indicating the bulk and interface contribution to overall electrical behavior of nanofiber mats. The bulk resistance was found to increase with decrease in temperature exhibiting typical semiconductor like behavior. The modulus analysis shows the non-Debye type conductivity relaxation in nanofiber mats. The ac conductivity spectrum obeyed the Jonscher power law. Analysis of frequency dependent ac conductivity revealed presence of the correlated barrier hopping (CBH) in nanofiber mats over the entire temperature range.
Imran, Z.; Rafiq, M. A.; Ahmad, M.; Rasool, K.; Batool, S. S.; Hasan, M. M.
Grain size effect on the nonlinear dielectric properties of barium titanate ceramics
The nonlinear dielectric properties of dense BaTiO{sub 3} ceramics with grain size of 1 {mu}m-90 nm were investigated. In the finest ceramics, the permittivity reduces below 1000 and a remarkable nonhysteretic linear dc-tunability [{epsilon}(E)] is obtained at high field, above 40 kV/cm. The observed behavior was explained by considering the nanostructured ceramic as a composite formed by ferroelectric grains, whose nonlinearity is reducing, and by low-permittivity nonferroelectric grain boundaries, whose volume fraction increases when decreasing the grain size. Reducing the grain size in ferroelectric dense materials is an alternative route to accomplish the application requirements: nonhysteretic tunability and permittivity below 1000.
Curecheriu, Lavinia; Mitoseriu, Liliana [Department of Physics, Alexandru Ioan Cuza University, Bv. Carol I No. 11, Iasi 700506 (Romania); Buscaglia, Maria Teresa; Buscaglia, Vincenzo [Institute of Energetics and Interphases (IENI)-CNR, Via De Marini No. 6, I-16149 Genoa (Italy); Zhao, Zhe [Department of Materials and Environmental Chemistry, University of Stockholm, SE-10691 Stockholm (Sweden)
Dielectric properties of lung tissue as a function of air content.
Dielectric measurements were made on lung samples with different electrode systems in the frequency range 5 kHz-100 kHz. In the case of plate electrodes and spot electrodes, the effects of electrode polarization were partly corrected. An air filling factor F is defined, which is determined from the mass and volume of the sample. The results indicate that the electrical properties of lung tissue are highly dependent on the condition of the tissue. Furthermore they show that the conductivity sigma as well as the relative permittivity epsilon r decreases with increasing F. This is discussed using histological material. Using a simple theoretical model, the decrease of sigma and epsilon r is explained by the thinning of the alveolar walls as well as by the deformation of the epithelial cells and blood vessels through the expansion of the alveoli. PMID:8346281
Nopp, P; Rapp, E; Pf³tzner, H; Nakesch, H; Ruhsam, C
Transmission properties near Dirac-like point in two-dimensional dielectric photonic crystals
NASA Astrophysics Data System (ADS)
We study the wave transport properties near the Dirac-like point at the Brillouin zone center in two-dimensional dielectric photonic crystals with finite thickness. Both simulations and microwave experiments confirm that the transmittance is nearly inversely proportional to the length (L) of the samples in the propagation direction near the Dirac-like point. This 1/L transmittance law comes from the conically shaped dispersion. Since the conical singularity at the Brillouin zone center corresponds to zero refractive index, the field at the Dirac-like point contains a basic component of nearly uniform field. In contrast, the field at the Dirac point in the corner of the hexagonal Brillouin zone contains a basic component of inhomogeneous standing-wave–like field.
Wang, X.; Jiang, H. T.; Yan, C.; Deng, F. S.; Sun, Y.; Li, Y. H.; Shi, Y. L.; Chen, H.
Anomaly of NdGaO3 single crystal dielectric properties in the temperature range 80¢300 K
The thermal behaviour of the dielectric properties of NdGaO3 single crystals has been measured from 80 to 300 K. An anomaly near 200 K in the temperature dependence of tan ?, magnetic susceptibility and thermal expansion is observed.
D. I. Savytskii; S. B. Ubizskii; A. O. Matkovskii; A. Suchocki; U. Bismayer; V. M. Pashkov; V. N. Borisov; A. N. Alexandrovskii; A. V. Soldatov
Microscopic properties of nanopore water from its time-dependent dielectric response J├╝rgen to show in Ra- man spectroscopy experiments for the first time that carbon nanotubes fill with water down, spanning huge orders of magnitude in time. Our simulations and analytical calculations show that nanopore
Dellago, Christoph
Microwaves can be a more efficient method than traditional thermal treatment to deliver the energy required for heating in solvent-oil extraction due to its volumetric, direct coupling with the material. An understanding of the behavior of dielectric properties of solvent-feedstock mixtures is important for designing and optimizing any microwave-based extraction process. In this study rice bran and soybean flour were mixed separately with four different solvents (methanol, ethanol, hexane and isopropanol) at different ratios (1:2, 1:1, 2:1 w/w). For the samples mixed with ethanol, the dielectric properties were measured at 23, 30, 40 and 50 degrees C, while for all other sample-solvent mixtures experiments were performed at room temperature. Dielectric properties were determined using a vector network analyzer and dielectric probe kit using the open-ended coaxial probe method in the frequency range of 300 MHz to 3 GHz. Results from the study indicate that dielectric constants were dependent on frequency and were strongly influenced by temperature, mix ratio and solvent type. The dielectric loss of all mixtures except those with hexane (which were virtually zero) varied with frequency and temperature, solvent type, and mix ratio. Most of the results presented are emphasized at 433, 915 and 2450 MHz, frequencies allocated by the Federal Communication Commission (F.C.C.) for microwave applications. The results of the study, presented here for the first time to our knowledge, will help in selection of appropriate solvent, mixing ratio and frequency for designing microwave-assisted oil extraction systems. PMID:20395139
Terigar, Beatrice G; Balasubramanian, Sundar; Boldor, Dorin
Dynamic and quasi-static mechanical properties of iron-nickel alloy honeycomb
NASA Astrophysics Data System (ADS)
Several metal honeycombs, termed Linear Cellular Alloys (LCAs), were fabricated via a paste extrusion process and thermal treatment. Two Fe-Ni based alloy compositions were evaluated. Maraging steel and Super Invar were chosen for their compatibility with the process and the wide range of properties they afforded. Cell wall material was characterized and compared to wrought alloy specifications. The bulk alloy was found to compare well with the more conventionally produced wrought product when porosity was taken into account. The presence of extrusion defects and raw material impurities were shown to degrade properties with respect to wrought alloys. The performance of LCAs was investigated for several alloys and cell morphologies. The results showed that out-of-plane properties exceeded model predictions and in-plane properties fell short due to missing cell walls and similar defects. Strength was shown to outperform several existing cellular metals by as much as an order of magnitude in some instances. Energy absorption of these materials was shown to exceed 150 J/cc at strains of 50% for high strength alloys. Finally, the suitability of LCAs as an energetic capsule was investigated. The investigation found that the LCAs added significant static strength and as much as three to five times improvement in the dynamic strength of the system. More importantly, it was shown that the pressures achieved with the LCA capsule were significantly higher than the energetic material could achieve alone. High pressures, approaching 3 GPa, coupled with the fragmentation of the capsule during impact increased the likelihood of initiation and propagation of the energetic reaction. This multi-functional aspect of the LCA makes it a suitable capsule material.
Clark, Justin L.
Low-temperature sintering and microwave dielectric properties of ZnTiO 3 -based LTCC materials
The low-temperature sintered microwave dielectric ceramics with composition of ZnTiO3-0.25TiO2 were prepared by adding a small amount of low-melting compounds CuO-V2O5-Bi2O3 (CVB). The phase relationship and dielectric properties as a function of sintering temperature and the additional amount\\u000a were studied. It is demonstrated that the addition of low-melting CVB can suppress the formation of Zn2TiO4 at low temperature, but decrease
Zhenxing Yue; Jing Yan; Fei Zhao; Zhilun Gui; Longtu Li
Synthesis and properties of dielectric Bi 2(Zn 1\\/3Nb 2\\/3) 2O 7 thin films
Crystalline, Bi2(Zn1\\/3Nb2\\/3)2O7, BiZN thin films can be easily obtained when the films were in-situ deposited at high enough substrate temperature 450¢600Ā░C (30 min). The optical parameters (N=n+ik) measured and analyzed by optical transmission spectroscopy are insensitive to the deposition parameters, provided that the films are crystalline. The dielectric properties converted from optical parameters are ??=4.75 and Q=325. The dielectric constant
Yi-Chun Chen; Hsiu-Fung Cheng; You-Ming Tsau; Petr Ku×el; Jan Petzelt; I-Nan Lin
NASA Astrophysics Data System (ADS)
In this study, we focus on deterioration in the shield property caused by penetrating a power wire through a transfixion hole. The shield structure of circular transfixion hole filled the space between the cable and the penetration part with dielectric and magnetic loss material is proposed, and shield property is evaluated by FDTD method and measuerment. As a result, it is confirmed that shield property decreases in case of penetrating a power wire through a circular transfixion hole compared with that of only circular hole, because this structure becomes circular coaxial line. Moreover, dielectric and magnetic loss material is filled in the space between the cable and the penetration part, it is clarified that shield property is improved about 20dB. Therefore, the effectiveness of this proposed structure to real transfixion hole can be confirmed quantitatively.
Ra, Fumio; Matsumoto, Kouta; Endo, Tetsuo; Hashimoto, Osamu
NASA Astrophysics Data System (ADS)
The European Rosetta spacecraft (s/c), launched in 2004, will be the first s/c to orbit a comet and place a lander module on its surface. In 2014, the s/c will rendezvous with the comet 67P/Churyumov-Gerasimenko and place the lander on its surface thereby allowing in situ and remote sensing of the comet nucleus. Two radio experiments, one passive (MIRO [1]) and one active (CONSERT [2]), are aboard the Rosetta s/c. MIRO, composed of two radiometers, with center band frequencies at 190 GHz and at 563 GHz to determine the brightness temperatures of the target surfaces and sub-surfaces, has already observed asteroids (2867) Steins [3] and (21) Lutetia [4]. CONSERT will investigate the deep interior of the nucleus using 90 MHz radio-waves transmitted from the orbiter through the nucleus and returned to the orbiter from the lander. To support interpretations of MIRO and CONSERT observations, a program of dielectric properties measurements is under development on a large range of frequencies encompassing those of the above-mentioned experiments. Several instruments for dielectric constant determination are available at IMS laboratory (Bordeaux, France): impedance analyzer, coaxial sensor, resonant cavities (measuring respectively at 100 MHz, 0.5-6 GHz, 1.2-13.4 GHz). Millimeter benches are available at both IMS and LERMA laboratories (measuring respectively at 30-110 GHz and 70-230 GHz). Taking into account the possible presence of regolith layers on the surface of asteroids or nuclei and the very low density of cometary nuclei [5], the dependence of the dielectric constant on the structure and porosity of given granular materials needs also to be investigated (while the thermal and hygrometric conditions are carefully monitored). We have already reported measurements obtained on various meteorites, possibly representative of some asteroid surfaces [6, 7]. We will also report systematic measurements obtained on a large sample of pyroclastic deposits from Etna, providing different sizes distributions (i.e. surface to volume ratios), and possibly porosities. Dielectric constant determination at 190 GHz typically suggests that the real part of dielectric constant slowly increases with grain size: 2.86 ▒ 0.06, 2.96 ▒ 0.02 and 3.13 ▒ 0.05 for sizes respectively lower than 50 Ąm, between 50 and 160 Ąm and between 160 and 355 Ąm. Additional series of measurements on compact and granular samples of meteoritic analogues, such as carbonaceous chondrites are also to take place. [1] Gulkis et al. , Space Sci. Rev., 128, 561-597, 2007. [2] Kofman et al. , Space Sci. Rev., 128, 413-432, 2007. [3] Gulkis et al. , Space. Sci. Rev., 58, 1077-1087, 2010. [4] Gulkis et al. , Space. Sci. Rev., doi: 10.1016/j.pss.2011.12.004, 2011. [5] Levasseur-Regourd et al. , Planet. Space Sci., 57, 221-228, 2009. [6] McFadden et al., 40th LPSC, 2887, 2009. [7] Brouet el al. , EPSC-DPS Joint Meeting, p. 1083, 2011.
Brouet, Y.; Levasseur-Regourd, A. C.; Encrenaz, P.; Gheudin, M.; Ciarletti, V.; Gulkis, S.; Jambon, A.; Ruffiķ, G.; Prigent, C.
Herein, poly(methyl methacrylate)-bismuth ferrite (PMMA-BFO) nanocomposites were successfully prepared by an in situ polymerization method for the first time. Initially, the as prepared bismuth ferrite (BFO) nanoparticles were dispersed in the monomer, (methyl methacrylate) by sonication. Benzoyl peroxide was used to initiate the polymerization reaction in ethyl acetate medium. The nanocomposite films were subjected to X-ray diffraction analysis (XRD), (1)H NMR, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), infrared spectroscopy (IR), dielectric and magnetic characterizations. The dielectric measurement of the nanocomposites was investigated at a frequency range of 10 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased value of the dielectric constant with an increase in the loading percentage of BFO as compared to pure PMMA, but also exhibited low dielectric loss values over a wide range of frequencies. The values of the dielectric constant and dielectric loss of the PMMA-BFO5 (5% BFO loading) sample at 1 kHz frequency was found be ~14 and 0.037. The variation of the ferromagnetic response of the nanocomposite was consistent with the varying volume percentage of the nanoparticles. The remnant magnetization (Mr) and saturation magnetization (Ms) values of the composites were found to be enhanced by increasing the loading percentage of BFO. The value of Ms for PMMA-BFO5 was found to be ~6 emu g(-1). The prima facie observations suggest that the nanocomposite is a potential candidate for application in high dielectric constant capacitors. Significantly, based on its magnetic properties the composite will also be useful for use in hard disk components. PMID:25050918
Tamboli, Mohaseen S; Palei, Prakash K; Patil, Santosh S; Kulkarni, Milind V; Maldar, Noormahmad N; Kale, Bharat B
Dielectric function and optical properties of quaternary AlInGaN alloys
The optical properties of quaternary Al{sub x}In{sub y}Ga{sub 1-x-y}N alloy films with 0.16
Sakalauskas, E.; Gobsch, G. [Institut fuer Physik, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Reuters, B.; Khoshroo, L. Rahimzadeh; Kalisch, H.; Vescan, A. [GaN Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); Heuken, M. [GaN Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath (Germany); Roeppischer, M.; Cobet, C. [Leibniz-Institut fuer Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Str. 9, 12489 Berlin (Germany); Goldhahn, R. [Institut fuer Physik, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Institut fuer Experimentelle Physik, Otto-von-Guericke-Universitaet Magdeburg, PF 4120, 39016 Magdeburg (Germany)
Mechanical property changes in porous low-k dielectric thin films during processing
NASA Astrophysics Data System (ADS)
The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.
Stan, G.; Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.
Dynamic and static shell properties of eggs provide important insight to egg quality. Understanding how processing and handling procedures affect both dynamic and static shell properties can enhance the safety and quality of eggs reaching the consumer. A study was conducted to determine if dynamic shell properties were altered due to modified pressure microcrack detection technology exposure in brown and white shell eggs. Three replicates of 100 eggs each of brown and white retail shell eggs were conducted. Dynamic stiffness (K(dyn)) and egg weight were monitored immediately before and after microcrack detection. No changes in K(dyn) or egg weight were detected for either shell color. Static compression shell strength and deformation were subsequently monitored and a correlation analysis conducted. A strong correlation (R(2) = 0.53; P < 0.0001) between K(dyn) and static compression shell strength was seen for extra large white shell eggs. A smaller (R(2) = 0.31; P < 0.0001) correlation was found for large brown eggs. The use of modified pressure microcrack detection technology did not affect shell dynamic properties. PMID:22991554
Jones, D R; Broussard, V; Lawrence, K C; Yoon, S C; Heitschmidt, G W
NASA Astrophysics Data System (ADS)
The present demand in the development of tunable devices and meta-materials require better understanding of the composite systems. Ferroelectric based composites with solubility or impurities doped interstitially satisfied the specific condition necessary for applications of e.g. frequency, bias, temperature, etc. On the other hand, many composite materials using coupling phenomena have been reported to have their effective properties surpassing the natural materials. The improvement of the properties of composite materials lies on the better understanding of their coupling effects. Conventional science tries to derive theories based on observation and materials characterizations. Taken advantage of the rapid growing computer technology, one used to say "impossible to be measured" or "impossible to see" can now be virtually characterized and visualized by simulation models. In this thesis, computer models of dielectric properties, piezoelectricity, magnetostriction and magnetoelectricity were constructed and verified. And subsequently the materials of interest were simulated and discussed. First, a three dimensional finite element model on dielectric properties of two phases or materials mixture was constructed. The effective permittivity and tan(delta) of Ba0.5Sr0.5 TiO3:MgO composite were simulated and compared with the experimental results. Structural design parameters concepts such as layers stacking, geometry effect, and effect of size of inclusion were visualized and then discussed. Subsequently, dielectric properties of Ba0.5Sr0.5TiO 3:MgO composite were examined changing their volume fraction using Monte Carlo simulation. The type of connectivity of the Ba0.5Sr 0.5TiO3:MgO composite was also discussed. On the other hand, finite element method with Monte Carlo simulation was conducted for the composition (x)Pb0.2Sr0.8TiO3:(1-x)MgO from x=0 to 1 in the paraelectric phase (from -50░C to 200░C), and the results were computed and compared with the experimental data. The temperature dependence of the relative permittivity of composites was well predicted up to 35.5% volume fraction of (Sr0.8Pb0.2)TiO3, which is sufficient for the composition of interest (usually a few percent of MgO). The simulation results showed little discrepancy as MgO volume fraction increases. Several possible factors resulting in the differences between experimental results and simulations were discussed. The empirically estimated critical volume fraction fc proposed by Wakino et al. for Pb0.2Sr 0.8TiO3:MgO composites was here estimated at ś0.9 throughout the Pb0.2Sr0.8TiO3 paraelectric phase temperature range. The results indicated that the critical volume fraction fc is a system varying parameter. In the final part of the thesis, a magnetostrictive and piezoelectric coupling model that estimates the electric/magnetic transfer efficiency (dE/dH) was presented. The magnetoelectric model was constructed based on two simulation models i.e. piezoelectric model and magnetostriction model. The piezoelectric model was constructed in dielectric model template adding the third rank piezoelectric effect. A commercial PZT transducer was experimentally measured with its properties. Related properties were then input for simulations and the resonance frequency of the specific PZT was successfully predicted. In addition, modes of resonance frequencies of the specific PZT were able to be visualized and identified. The magnetostriction model was constituted with its forth rank property. Mathematical formula and a modified model based on Langevin theory were appended to the original piezoelectric and magnetostrictive equations to simulate the saturated elastic responses in the coupled systems. A laminated Terfenol-D/PZT/Terfenol-D magnetoelectric composite system was modeled that permits simulated evaluation of coupling properties e.g., magnetostrictive coefficient and strain vs. magnetic field response. The electromagnetic transfer efficiency of the modeled results was in good agreement with experimental value in literature. Magnetostric
Wang, Hsiao-Yuan
Influence of stoichiometry on the dielectric properties of sputtered strontium titanate thin films
The dielectric permittivity, dielectric quality factor (inverse dielectric loss), and lattice parameter of 140 nm sputtered SrTiO3 films were dependent on the oxygen partial pressure and total chamber pressure (O2+Ar) during film growth. Films were grown at 25 and 75 mTorr (mT) in an oxygen rich and oxygen deficient sputtering gas environment concurrently on (100) SrTiO3 and (111) Pt\\/(0001) Al2O3
T. R. Taylor; P. J. Hansen; N. Pervez; B. Acikel; R. A. York; J. S. Speck
Dielectric constants and indices of refraction of aqueous mixtures of the homologous series of polyoxy-ethene glycol mono-n-butyl ethers C4H9O(CH2CH2O)mH (where m = 1 to 3) were measured. From the experimental data, excess dielectric permittivities, dielectric molar susceptibilities, molar and molar orientational polarizabilities were evaluated. Also excess Lorentz-Lorentz molar refractions were evaluated and the results were discussed in terms of departure
Joseph Macneil; Dale Turner; R. Palepu
The dielectric properties of TeO 2¢P 2O 5 glasses
The dielectric constant and the tangent loss were measured for the TeO2¢P2O5 glass system in the frequency range 0.1¢10kHz at different isotherms. The dielectric constant and the tangent loss decreased with increasing frequency, while both of them increased with increasing temperature. The decrease of the dielectric constant with increasing frequency was attributed at low frequency to the contribution of all
M. M. Elkholy; L. M. Sharaf El-Deen
NASA Astrophysics Data System (ADS)
Thin films of bismuth layer-structured dielectrics (BLSDs), CaBi4Ti4O15, and SrBi4Ti4O15, were prepared by a chemical solution deposition (CSD) technique on various substrates, such as (111)Pt/TiO2/(100)Si, (100)LaNiO3/(111)Pt/TiO2/(100)Si, and (100)SrRuO3?(100)SrTiO3 substrates. Conductive perovskite oxide LaNiO3 with (100) preferential crystal orientation was introduced into the interface between the BLSD film and the (111)Pt/TiO2/(100)Si substrate to control the crystal orientation of BLSD by lattice matching between pseudo-perovskite blocks in the BLSD crystal and the (100)LaNiO3 plane with the perovskite structure. The (00l) planes of BLSD crystals were preferentially oriented on the substrate surface of the (100)LaNiO3/(111)Pt/TiO2/(100)Si, whereas randomly-oriented BLSD crystals with lower crystallinity were only obtained on the surface of (111)Pt/TiO2/(100)Si substrate. The (001)-oriented BLSD films exhibited the leakage current densities below 10-7 A/cm2 at ▒50 kV/cm, which is significantly lower than those for randomly-oriented films, above 10-6 A/cm2, The room-temperature dielectric constants (?r) of CaBi4Ti4O15 and SrBi4Ti4O15 thin films on the (100)LaNiO3/(111)Pt/TiO2/(100)Si substrate were both approximately 250, while those on the (100)SrRuO3?(100)SrTiO3 substrate were approximately 220. The temperature dependence of the capacitances for the CaBi4Ti4O15 and SrBi4Ti4O15 films on the (100)LaNiO3/(111)Pt/TiO2/(100)Si substrate were approximately +17 and +10%, respectively, in the temperature range from 25 to 400 ░C. These values were slightly larger than those of epitaxial BLSD films, but smaller than those of (Ba,Sr)TiO3 films.
Mizutani, Yuki; Kiguchi, Takanori; Konno, Toyohiko J.; Funakubo, Hiroshi; Uchida, Hiroshi
Dielectric properties of (Ba0.60,Sr0.40)TiO3 thin films on NdGaO3 substrates at 10 GHz
This work investigates the effects of anisotropic epitaxial strains on the microwave frequency dielectric response of BST (60\\/40) thin films. Dielectric properties such as permittivity and tunability along the , and crystallographic directions correlate well with the variation of elastic strain energy as a function of film thickness. We demonstrate unequivocally that the maximum permittivity and tunability is obtained along
W. K. Simon; E. K. Akdogan; J. Belotti; A. Safari
Synthesis and frequency-dependent dielectric properties of epitaxial La1.875Sr0.125NiO4 thin films
NASA Astrophysics Data System (ADS)
Epitaxial thin films of La1.875Sr0.125NiO4 (lanthanum strontium nickelate, LSNO) have been synthesized by sputtering onto single crystal oxide substrates and their structural and dielectric properties are reported. High dielectric constants on the order of 107 have been measured up to 1 MHz in interdigitated capacitors with a frequency dependence that correlates with substrate imposed strain and texture. The observation of a high dielectric constant albeit with moderate loss tangent at high frequencies motivates further explorations of charge ordering phenomena in such complex oxides and serves to examine size effects on dielectric response by comparison with studies on bulk single crystal LSNO.
Podpirka, Adrian; Tselev, Alexander; Ramanathan, Shriram
To ensure maximum productivity of recombinant proteins it is desirable to prolong cell viability during a mammalian cell bioprocess, and therefore important to carefully monitor cell density and viability. In this study, five different and independent methods of monitoring were applied to Chinese hamster ovary (CHO) cells grown in a batch culture in a controlled bioreactor to determine cell density and/or cell viability. They included: a particle counter, trypan blue exclusion (Cedex), an in situ bulk capacitance probe, an off-line fluorescent flow cytometer, and a prototype dielectrophoretic (DEP) cytometer. These various techniques gave similar values during the exponential growth phase. However, beyond the exponential growth phase the viability measurements diverged. Fluorescent flow cytometry with a range of fluorescent markers was used to investigate this divergence and to establish the progress of cell apoptosis: the cell density estimates by the intermediate stage apoptosis assay agreed with those obtained by the bulk capacitance probe and the early stage apoptosis assay viability measurements correlated well with the DEP cytometer. The trypan blue assay showed higher estimates of viable cell density and viability compared to the capacitance probe or the DEP cytometer. The DEP cytometer measures the dielectric properties of individual cells and identified at least two populations of cells, each with a distinct polarizability. As verified by comparison with the Nexin assay, one population was associated with viable (non-apoptotic) cells and the other with apoptotic cells. From the end of the exponential through the stationary and decline stages there was a gradual shift of cell count from the viable into the apoptotic population. However, the two populations maintained their individual dielectric properties throughout this shift. This leads to the conclusion that changes in bulk dielectric properties of cultures might be better modeled as shifts in cells between different dielectric sub-populations, rather than assuming a homogeneous dielectric population. This shows that bulk dielectric probes are sensitive to the early apoptotic changes in cells. DEP cytometry offers a novel and unique technology for analyzing and characterizing mammalian cells based on their dielectric properties, and suggests a potential application of the device as a low-cost, label-free, electronic monitor of physiological changes in cells. PMID:23818314
Braasch, Katrin; Nikolic-Jaric, Marija; Cabel, Tim; Salimi, Elham; Bridges, Greg E; Thomson, Doug J; Butler, Michael
NASA Astrophysics Data System (ADS)
Barium titanate (BaTiO3) ceramics co-doped with rare-earth elements were investigated in terms of selective substitution and tetragonality. The dielectrics were designed by addition of various Dy2O3 and Tm2O3 contents, for a total of 1 mol. % concentration, and analyzed in a temperature range from -55░C to 150░C. The dielectric constant of the 0.7 mol. % Dy2O3 and the 0.3 mol. % Tm2O3 co-doped BaTiO3 was 2250, which was about 27% higher than those of specimens doped with 1 mol. % Tm2O3 and 1 mol. % Dy2O3 at room temperature. The tendency of dielectric properties was verified through the changes of lattice parameters and binding energy. The substitution of Dy3+ led to a decrease of tetragonality and grain growth; however, amphoteric substitution caused by the co-doping of Dy2O3 and Tm2O3 compensated for those adverse effects. It can be concluded that the improvement of dielectric properties originated from the increase of the site substitution rate of Dy3+ and Tm3+ ions according to the ionic size the in rare-earth doped BaTiO3 system.
Kim, Jungdae; Kim, Dowan; Kim, Jinseong; Kim, Yong-Nam; Hui, K. N.; Lee, Heesoo
Static Properties and Stark Effect of the Ground State of the HD Molecular Ion
NASA Technical Reports Server (NTRS)
We have calculated static properties of the ground state of the HD(+) ion and its lowest-lying P-state without making use of the Born-Oppenheimer approximation, as was done in the case of H2(+) and D2(+) [Phys. Rev. A 58, 2787 (1998)]. The ion is treated as a three-body system whose ground state is spherically symmetric. The wavefunction is of generalized Hylleraas type, but it is necessary to include high powers of the internuclear distance to localize the nuclear motion. We obtain good values of the energies of the ground S-state and lowest P-state and compare them with earlier calculations. Expectation values are obtained for various operators, the Fermi contact parameters, and the permanent quadrupole moment. The cusp conditions are also calculated. The polarizability was then calculated using second-order perturbation theory with intermediate P pseudostates. Since the nuclei in HD(+) are not of equal mass there is dipole coupling between the lowest two rotational states, which are almost degenerate. This situation is carefully analyzed, and the Stark shift is calculated variationally as a function of the applied electric field.
Bhatia, A. K.; Drachman, Richard J.
Static properties and multiaxial strength criterion for design of composite automotive structures
The Durability of Lightweight Composite Structures Project was established at Oak Ridge National Laboratory (ORNL) by the US Department of Energy to provide the experimentally-based, durability-driven design guidelines necessary to assure long-term structural integrity of automotive composite components. The initial focus of the ORNL Durability Project was on one representative reference material -- an isocyanurate (polyurethane) reinforced with continuous strand, swirl-mat E-glass. The present paper describes tensile, compressive, flexure, and shear testing and results for the reference composite. Behavioral trends and proportional limit are established for both tension and compression. Damage development due to tensile loading, strain rate effects, and effects of temperature are discussed. Furthermore, effects on static properties of various fluids, including water at room and elevated temperatures, salt water, antifreeze, windshield washer fluid, used motor oil, battery acid, gasoline, and brake fluid, were investigated. Effects of prior loading were evaluated as well. Finally, the effect of multiaxial loading on strength was determined, and the maximum shear strength criterion was identified for design.
Ruggles, M.B.; Yahr, G.T.; Battiste, R.L.
Efficient numerical method for simulating static and dynamic properties of superfluid helium
NASA Astrophysics Data System (ADS)
Density functional theory (DFT) offers computationally affordable way of describing static and dynamic properties of superfluid 4He. In general, the DFT models yield single particle-like Schr÷dinger equations with a nonlinear potential term that accounts for all the many-body interactions. The resulting equations can be solved for small amplitude plane wave excitations in the bulk whereas fully numerical solution must be sought in more complicated cases. In this paper we propose a numerical method that can be used in solving the time-dependent nonlinear Schr÷dinger equation in both real and imaginary times. The method is based on operator splitting technique where each component operator is treated with a unitary semi-implicit Crank-Nicolson scheme. In order to increase the stability of the method for complex valued nonlinear potentials, a predict-correct scheme is employed in the simulations. The numerical calculations indicate that the scheme is numerically sufficiently stable and well behaving, exhibits high degree of parallelism, and produces results in agreement with the existing numerical data. In the numerical examples we apply the method to obtain dispersion relation of the bulk liquid and to calculate solvation and absorption spectrum of atomic boron solvated in superfluid helium.
Lehtovaara, L.; Kiljunen, T.; Eloranta, J.
Vectran Fiber Time-Dependent Behavior and Additional Static Loading Properties
NASA Technical Reports Server (NTRS)
Vectran HS appears from literature and testing to date to be an ideal upgrade from Kevlar braided cords for many long-term, static-loading applications such as tie-downs on solar arrays. Vectran is a liquid crystalline polymer and exhibits excellent tensile properties. The material has been touted as a zero creep product. Testing discussed in this report does not support this statement, though the creep is on the order of four times slower than with similar Kevlar 49 products. Previous work with Kevlar and new analysis of Vectran testing has led to a simple predictive model for Vectran at ambient conditions. The mean coefficient of thermal expansion (negative in this case) is similar to Kevlar 49, but is not linear. A positive transition in the curve occurs near 100 C. Out-gassing tests show that the material performs well within parameters for most space flight applications. Vectran also offers increased abrasion resistance, minimal moisture regain, and similar UV degradation. The effects of material construction appear to have a dramatic effect in stress relaxation for braided Vectran. To achieve the improved relaxation rate, upgrades must also examine alternate construction or preconditioning methods. This report recommends Vectran HS as a greatly improved replacement material for applications where time-dependent relaxation is a major factor.
Fette, Russell B.; Sovinski, Marjorie F.
NASA Technical Reports Server (NTRS)
The effect of substituting iron by aluminum in polymorphs of Fe2O3 and FeOOH on their reflectivity characteristics was investigated by comparing data on visible and NIR reflectivities and on static magnetic, XRD, and Moessbauer properties for a family of aluminum-substituted hematites alpha-(Fe,Al)2O3, with compositions where the values of the Al/(Al+Fe) ratio were up to 0.61. Samples were prepared by oxidation of magnetite, dehydroxylation of goethite, and direct precipitation. The analytical methods used for obtaining diffuse reflectivity spectra (350-2200 nm), Moessbauer spectra, and static magnetic data are those described by Morris et al. (1989).
Morris, Richard V.; Schulze, Darrell G.; Lauer, Howard V., Jr.; Agresti, David G.; Shelfer, Tad D.
The effect of aluminium doping, as an acceptor impurity on the polycrystalline cesium vanadate has been studied in the temperature range covering their transition points. The dielectric constant is measured by 'comparison of capacities' while the coercive field is evaluated using hysteresis loop. It is seen that the dielectric constant as well as the coercive field are remarkably depending on
S. P. Rasal; V. V. Patil; A. J. Kulkarni; S. H. Chavan
NASA Astrophysics Data System (ADS)
The mechanical properties of laser welded joints under impact loadings such as explosion and car crash etc. are critical for the engineering designs. The hardness, static and dynamic mechanical properties of AISI304 and AISI316 L dissimilar stainless steel welded joints by CO2 laser were experimentally studied. The dynamic strain-stress curves at the strain rate around 103 s-1 were obtained by the split Hopkinson tensile bar (SHTB). The static mechanical properties of the welded joints have little changes with the laser power density and all fracture occurs at 316 L side. However, the strain rate sensitivity has a strong dependence on laser power density. The value of strain rate factor decreases with the increase of laser power density. The welded joint which may be applied for the impact loading can be obtained by reducing the laser power density in the case of welding quality assurance.
Wei, Yan-Peng; Li, Mao-Hui; Yu, Gang; Wu, Xian-Qian; Huang, Chen-Guang; Duan, Zhu-Ping
A study of thermal, dielectric and magnetic properties of strontium malonate crystals
NASA Astrophysics Data System (ADS)
Crystals of strontium malonate (SrC 3H 2O 4) were grown in silica gel by the single diffusion technique. The thermo gravimetric (TG), differential thermal analysis (DTA) and differential scanning calorimetric (DSC) studies were carried out to investigate the thermal stability of the crystal. The dielectric behavior of the title compound crystal was investigated by measuring the dielectric parameters - dielectric constant, dielectric loss and AC conductivity as a function of four frequencies -1 kHz, 10 kHz, 100 kHz and 1 MHz at temperatures ranging from 50 to 170 ░C. Results indicate that the title compound is thermally stable up to about 409 ░C and is a promising low ?r-value dielectric material. The magnetic behavior of the crystal was also explored using a vibrating sample magnetometer.
Mathew, Varghese; Jacob, Sabu; Mahadevan, C. K.; Abraham, K. E.
NASA Astrophysics Data System (ADS)
Cobalt ferrite is synthesized by using low temperature auto combustion and high temperature ceramic methods. The prepared samples have values of lattice constant equal to 8.40 ┼ and 8.38 ┼ for auto combustion and ceramic methods respectively. The FTIR spectrum of samples of the auto combustion method shows a high frequency vibrational band at 580 cm-1 assigned to tetrahedral site and a low frequency vibrational band at 409 cm-1 assigned to octahedral site which are shifted to 590 cm-1 and 412 cm-1 for the ceramic method sample. SEM micrographs of samples show a substantial difference in surface morphology and size of the grains between the two methods. The frequency dependent dielectric constant and ac conductivity of the samples measured from 1 Hz to 2 MHz at room temperature are reported. The room temperature magnetic hysteresis parameters of the samples are measured using VSM. The measured values of saturation magnetization, coercivity and remanent magnetization are 42 emu/g, 1553 Oe, 18.5 emu/g for the auto combustion method, 66.7 emu/g, 379.6 Oe, and 17.3 emu/g for the ceramic method, respectively. The difference in preparation methods and size of the grains causes interesting changes in electrical and magnetic properties.
Murugesan, C.; Perumal, M.; Chandrasekaran, G.
NASA Astrophysics Data System (ADS)
Nickel ferrite nanoparticles were synthesized by wet chemical co-precipitation method and the corresponding temperature dependent structural, magnetic and optical properties of these nanoparticles have been investigated. X-ray diffraction patterns show the single phase cubic spinal crystal structure belonging to the space group Fd3m. The average crystallite size varies in the range 8-20 nm with varying sintering temperature. Raman spectroscopy exhibits a doublet-like peak behaviour which indicates the presence of mixed spinel structure. The saturation magnetization, coercivity and remanence increase with increasing sintering temperature from 250 to 550 ░C. The non-saturation and low values of magnetization at high fields indicate the strong surface effects to magnetization in NiFe2O4 nanoparticles. The g-value calculated from electron spin resonance spectrum indicates the transfer of divalent metallic ion from octahedral to tetrahedral site (i.e. mixed spinel structure). The dielectric permittivity, loss tangent and ac conductivity measurements show strong temperature dependence at all frequencies. The observed ac conductivity response suggests that the conduction in ferrite nanoparticles is due to feeble polaron hopping between Fe3+/Fe2+ ions. Room temperature UV-vis diffuse spectra indicate that NiFe2O4 is an indirect band gap material with band gap ranges from 1.27 to 1.47 eV with varying sintering temperature. The photoluminescence study clearly indicates that the Ni2+ ions occupy both octahedral and tetrahedral sites confirming mixed spinel structure.
Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Srivastava, Geetika; Jewariya, Mukesh; Singh, V. N.
NASA Astrophysics Data System (ADS)
In this study, the properties of pure and GdCl3-doped polyvinylidene fluoride (PVDF) films were investigated. X-ray diffraction revealed that the PVDF was composed of mixed ? and ? phases. Adding GdCl3 to PVDF decreased the crystallinity of the polymer matrix. At room temperature, in the ultraviolet-visible range both the absorbance (a) and extinction coefficient (k) of PVDF decreased with GdCl3 content, demonstrating that the optical response of the doped films improved because of increasing optical energy gap (Eg). We also measured the dielectric loss (??), electric modulus (M?), and ac conductivity (?ac) at 300-450 K and 0.1-3000 kHz. The pure and doped PVDF exhibited different relaxation processes. The activation energy (Ea) of the ?c relaxation decreased with increasing GdCl3 content, following an Arrhenius relationship. The behavior of the ac conductivity revealed that the conduction mechanism for studied films followed correlated barrier hopping model. The hopping distance (R) was calculated at different temperatures for all investigated samples.
El-Sayed, Somyia
Polyamide 12/ fullerene C60 composites: Investigation on their mechanical and dielectric properties
NASA Astrophysics Data System (ADS)
The effect of fullerene C60 on mechanical properties of polymer nanocomposites based on PA12 was investigated. The nanocomposites were prepared by in situ polymerization. The Young's modulus and tensile strength of the polymer nanocomposites are improved by about 20% with loading of 0.02-0.08 wt.% the fullerene C60. Dielectric spectroscopy was used to investigate the influence of nanoparticles on the relaxation processes in polymer matrix. The segmental relaxation processes become faster with the fullerene C60 addition, an effect associated with a decrease of the glass transition temperature. In contrast, the secondary or ? relaxation process of PA12/ fullerene C60 nanocomposites was observed to slow down with addition of fullerene C60. These observations indicate that fullerene C60 as filler has an effect opposite to antiplasticizing that slow down the secondary relaxation (stiffening the material) in the glass state, while at the same time reducing the alpha relaxation time associated with cooperative segmental motions. It behaviour can be connected with inclusion complex formation between PA12 and fullerene C60.
Zuev, Vjacheslav V.
Structural and electric-dielectric properties of some bismuth -phosphate glasses
NASA Astrophysics Data System (ADS)
In the present study, glasses with composition XBi2O3 (60-X)P2O5 20Fe3O4 20Li2O (0?X?15) mol% have been prepared by the conventional melt quenching technique. The IR studies show the presence of FeO4, FeO6, BiO6, PO3, P?O and PO4 structural groups. The hyperfine structure of these glasses is investigated using M÷ssbauer spectroscopy. ME spectroscopy indicated the presence of two different oxidation states of iron (Fe2+ and Fe3+). The ferrous ions Fe2+ occupied tetrahedral coordination states, while the ferric ions Fe3+ occupied both tetrahedral and octahedral coordination states. The effect of partial replacement of P2O5 by Bi2O3 on the electric-dielectric properties is studied in more details. It is found that, unmonotonic variation in the ?dc, (?D/2), ?ac(?), ?1(?), and ?2(?), as a function of Bi2O3 contents. Also it is found that, the power law exponent, s, is temperature dependent and the CBH model is the most applicable conduction mechanism in all glass samples. Pseudo Cole-Cole diagram of the investigated glassy samples exhibit similar behavior where all plots show a single semicircle indicating a single relaxation process.
Shapaan, M.; El-Badry, S. A.; Mostafa, A. G.; Hassaan, M. Y.; Hazzaa, M. H.
The magnetoresonance and dielectric properties of a number of crystals of a new family of multiferroics, namely, rare-earth ferroborates RFe{sub 3}(BO{sub 3}){sub 4} (R = Y, Eu, Pr, Tb, Tb{sub 0.25}Er{sub 0.75}), are studied in the sub-millimeter frequency range ({nu} = 3-20 cm{sup -1}). Ferroborates with R = Y, Tb, and Eu exhibit permittivity jumps at temperatures of 375, 198, and 58 K, respectively, which are caused by the R32 {yields} P3{sub 1}21 phase transition. Antiferromagnetic resonance (AFMR) modes in the subsystem of Fe{sup 3+} ions are detected in the range of anti-ferromagnetic ordering (T < T{sub N} = 30-40 K) in all ferroborates that have either an easy-plane (Y, Eu) or easy-axis (Pr, Tb, Tb{sub 0.25}Er{sub 0.75}) magnetic structure. The AFMR frequencies are found to depend strongly on the magnetic anisotropy of a rare-earth ion and its exchange interaction with the Fe subsystem, which determine the type of magnetic structure and the sign and magnitude of an effective anisotropy constant. The basic parameters of the magnetic interactions in these ferroborates are found, and the magnetoelectric contribution to AFMR is analyzed.
Kuz'menko, A. M.; Mukhin, A. A., E-mail: firstname.lastname@example.com; Ivanov, V. Yu. [Russian Academy of Sciences, Institute of General Physics (Russian Federation); Kadomtseva, A. M. [Moscow State University (Russian Federation); Lebedev, S. P. [Russian Academy of Sciences, Institute of General Physics (Russian Federation); Bezmaternykh, L. N. [Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation)
Although electrical discharge machining is essentially a material removal process, efforts have been made in the recent past\\u000a to use it as a surface treatment method. An additive powder in the dielectric medium affects the sparking action and helps\\u000a in improving the surface properties. It may melt at the high temperature of the plasma channel and alloy with the machined
Sanjeev Kumar; Rupinder Singh
This study investigates the dielectric, magnetic, and microwave absorbing properties of Sm2O3-filled multi-walled carbon nanotubes (MWCNTs) synthesized by wet chemical method. The complex permittivity and permeability were measured at a microwave frequency range of 2¢18ĀGHz. Sm2O3 nanoparticles encapsulated in the cavities enhance the magnetic loss of MWCNTs. The calculated results indicate that the bandwith of absorbing peak of the modified
Lan Zhang; Hong Zhu
Modification of the hydrophilic properties of polypropylene (PP) films has been investigated using the postdischarge region of a pulsed nitrogen-based dielectric barrier discharge under atmospheric-pressure conditions. Results show that, for the stationary PP films, the contact angle (CA) decreases dramatically from 103░ (untreated) to less than 30░ (treated) with a wide range of O2\\/N2 ratios (<; 1%) and treating distances
Ming-Hung Chiang; Kuo-Chi Liao; I-Min Lin; Chi-Chang Lu; Hao-Yuan Huang; Chi-Liang Kuo; Jong-Shinn Wu
NASA Astrophysics Data System (ADS)
The dielectric properties of dual-layer PZT/ZrO2 thin films were measured at microwave frequencies in both a metal-insulator-metal (MIM) capacitor and a coplanar waveguide (CPW) up to 50 GHz. Both PZT and ZrO2 films were prepared by the chemical solution deposition method. The measured dielectric loss of the PZT/ZrO2 film was approximately 0.08 at 30 GHz, much lower than that of typical PZT thin films. The dielectric constants obtained using the MIM capacitor with 360 nm PZT/65 nm ZrO2 and using the CPW with 420 nm PZT/280 nm ZrO2 were 47 and 130, respectively, at 50 GHz. Capacitance tunability was ~30% at +25 V and up to 50 GHz. The measured values obtained indicate that PZT/ZrO2 thin films may be suitable for the use of dielectric layers in tunable RF devices and RF MEMS capacitive switches operating at millimetre wave frequencies.
Min, D.; Hoivik, N.; Jensen, G. U.; Tyholdt, F.; Hanke, U.
NASA Astrophysics Data System (ADS)
Mn substituted ZnFe2O4 nanoparticles were prepared by the auto-combustion method using different fuel ratios of 50%, 75% and 100%.The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectrum (EDX). Also, the dielectric behaviors of the samples were investigated for different annealing temperatures. The X-ray diffraction patterns indicated that the annealed samples resulted in the formation of crystalline powder and the presence of ?-Fe2O3 as a secondary phase. The average crystallite sizes of the samples are from ~12 to 60 nm. The external morphology and microstructure of the samples are tested by SEM and TEM. The effect of annealing temperature and particle size on dielectric properties such as dielectric constant (?) and dielectric loss (D) of the spinel MnxZn1-xFe2O4 nanoparticles was measured using impedance analyzer in the frequency range 100 kHz-5 MHz.
Ranjith Kumar, E.; Jayaprakash, R.
AC conductivity and dielectric properties of amorphous Ge xSb 40-xSe 60 thin films
NASA Astrophysics Data System (ADS)
Measurements of AC conductivity and dielectric properties have been made for chalcogenide film samples of Ge xSb 40-xSe 60 (with x=0, 10 and 20 at%) at different temperatures (303-393 K) and various frequencies (10 2-10 5 Hz). It was found that the AC conductivity obeys the law ?( ?, T)= A?s. The exponent s<1 was found to decrease with increasing temperature through the entire range of temperatures and frequencies. This is interpreted by the correlated barrier hopping (CBH) model. Values of dielectric constant ?1 and dielectric loss ?2 were found to decrease with frequency and increase with temperature. The maximum barrier height WM was calculated from dielectric measurements according to the Guintini equation. It was found that the obtained value of Wm agrees with that proposed by the theory of hopping of charge carriers over potential barrier as suggested by Elliott in case of chalcogenide glasses. The density of localized states N( EF) has also been calculated for the studied compositions. The effect of decreasing the Sb content at the expense of the Ge content was investigated for the obtained results of the studied parameters.
Atyia, H. E.; Farid, A. M.; Hegab, N. A.
NASA Astrophysics Data System (ADS)
In situ polymerized polyimide/TiO2 (PI/TiO2) nanocomposite films with good electrical aging resistance are studied. Space charge distribution in the PI/TiO2 nanocomposite films are measured using the pulsed electroacoustic method. Dielectric properties of the films are measured in the frequency range of 102 Hz-106 Hz by an impedance analyzer (Agilent 4294A) at room temperature. These nanocomposite films are also characterized by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). It is demonstrated that the nano-TiO2 particles strongly affect dielectric breakdown, lifetime and space charge distribution, and increase the voltage endurance of the nanocomposite films significantly. SEM analyses show that the nanocomposite films are destroyed after corona aging. The relation of space charge distribution with the concentration of the nano-TiO2 particles and the aging time is explored. Results show that an increase in dielectric permittivity of the nanocomposite films is observed with increasing filler concentration. However, the accumulation of space charge decreases with increasing nano-TiO2 particles concentration for the same corona aging time, and depends on the dielectric permittivity of the nanocomposite films.
Zha, Jun-Wei; Dang, Zhi-Min; Song, Hong-Tao; Yin, Yi; Chen, George
Manganese (Mn) substituted cobalt ferrites (CoFe{sub 2?x}Mn{sub x}O{sub 4}, referred to CFMO) were synthesized and their structural, magnetic, and dielectric properties were evaluated. X-ray diffraction measurements coupled with Rietveld refinement indicate that the CFMO materials crystallize in the inverse cubic spinel phase. Temperature (T?=?300?K and 10?K) dependent magnetization (M(H)) measurements indicate the long range ferromagnetic ordering in CoFe{sub 2?x}Mn{sub x}O{sub 4} (x?=?0.00¢0.15) ferrites. The cubic anisotropy constant (K{sub 1}(T)) and saturation magnetization (M{sub s}(T)) were derived by using the ōlaw of approachö to saturation that describes the field dependence of M(H) for magnetic fields much higher than the coercive field (H{sub c}). Saturation magnetization (M{sub s}), obtained from the model, decreases with increasing temperature. For CoFe{sub 2}O{sub 4}, M{sub s} decreases from 3.63??{sub B} per formula unit (f.u.) to 3.47??{sub B}/f.u. with increasing temperature from 10 to 300?K. CFMO (0.00¢0.15) exhibit the similar trend while the magnitude of M{sub s} is dependent on Mn-concentration. M{sub s}-T functional relationship obeys the Bloch's law. The lattice parameter and magnetic moment calculated for CFMO reveals that Mn ions occupying the Fe and Co position at the octahedral site in the inverse cubic spinel phase. The structure and magnetism in CFMO are further corroborated by bond length and bond angle calculations. The dielectric constant dispersion of CFMO in the frequency range of 20?Hz¢1?MHz fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived from modeling the experimental data are ?10{sup ?4}?s and ?0.35(▒0.05), respectively.
Ramana, C. V., E-mail: email@example.com; Kolekar, Y. D.; Kamala Bharathi, K. [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States); Sinha, B. [Functional Nanopowder Material Division, Korea Institute of Material Science, Changwon 642-831, Gyeongnam (Korea, Republic of); Ghosh, K. [Department of Physics, Astronomy and Materials Science, Missouri State University, Springfield, Missouri 65897 (United States)
The objective of the present study was to examine the influence of the level of added water (21¢29%), fat (12.4¢29.7%) and salt (0.4¢2.4%) on radio frequency (RF) and microwave (MW) dielectric properties. Selected thermal properties and temperature rises (?T) following standardised MW or RF heating protocols were also measured. Results revealed that added salt had a major impact on dielectric
Lu Zhang; James G. Lyng; Nigel P. Brunton
We have developed a system to measure the changes due to heating to high temperatures in the dielectric properties of tissues in the radio-frequency range. A two-electrode arrangement was connected to a low-frequency impedance analyser and used to measure the dielectric properties of ex vivo porcine kidney and fat at 460 kHz. This frequency was selected as it is the
Mihaela Pop; Andrea Molckovsky; Michael C Kolios; Michael A S Jewett; Michael D Sherar
Plasma treatment of parylene-C surfaces not only causes structural modification of the surface during the plasma exposure, but also leaves active sites on the surfaces, which decreases the dielectric properties. In this work, the effects of oxygen, argon\\/hydrogen and fluorine plasma treatment on the surface and dielectric properties of parylene-C thin films were investigated using Fourier transform-IR spectroscopy, energy dispersive
A Kahouli; A Sylvestre; J-F Laithier; S Pairis; J-L Garden; E Andrķ; F Jomni; B Yangui
Effect of dielectric thin films on reflection properties of metal hole arrays
NASA Astrophysics Data System (ADS)
We study the effect of a dielectric film attached to the surface of a metal hole array (MHA) on the reflection spectrum in the terahertz (THz) region. The frequency of the reflection dip, attributed to the excitation of surface waves in the vicinity of the MHA surface, shifts to lower frequencies with increasing dielectric film thickness. This resonant characteristic of MHAs can be applied to highly sensitive THz sensing for samples attached to the MHA surface. We also investigate the dependence of the reflection spectrum on the MHA's thickness and the side to which the dielectric film is attached.
Miyamaru, Fumiaki; Sasagawa, Yuki; Takeda, Mitsuo Wada
NASA Astrophysics Data System (ADS)
We report an ab initio molecular dynamics study of the static, dynamic and electronic properties of the liquid BixLi1-x alloy, which is a complex binary system with a marked tendency to heterocoordination. The calculated total static structure factors are in good agreement with the available experimental data. The partial dynamic structure factors exhibit side peaks indicative of propagating density fluctuations, and for some concentrations we have found a density fluctuation mode with phase velocity greater than the hydrodynamic sound velocity. We have also evaluated other dynamical properties such as the diffusion coefficients, the shear viscosity and the adiabatic sound velocity. The electronic density of states show that the liquid BixLi1-x alloy has a metallic character, although with strong deviations from the free-electron parabolic curve. The results reported improve the understanding of binary liquid alloys with both fast and slow propagating collective modes.
Souto, J.; Alemany, M. M. G.; Gallego, L. J.; Gonzßlez, L. E.; Gonzßlez, D. J.
Effects of deep cryogenic treatment on static mechanical properties of 18NiCrMo5 carburized steel
In consideration of the raising interest about the application of the deep cryogenic treatment (DCT) on materials, its effects on the static mechanical properties of a commercial gear carburized steel (18NiCrMo5) are investigated through hardness and tensile tests followed by optical fractographic observations. The present study focuses on the comparison between the results given by different sequences of DCT and
Paolo Baldissera; Cristiana Delprete
Static properties of the nucleon in the Faddeev approach based on the Nambu--Jona-Lasinio model
A general framework to compute matrix elements of operators between relativistic three-quark bound states is presented and used to investigate static properties of the nucleonic solution to the Faddeev equation. The Ward-Takahashi identity in the three-quark system is derived and the violation of gauge invariance due to a Euclidean cut-off is investigated. Results for the axial vector coupling constants and quark condensates are presented and discussed in comparison to the additive diquark-quark model.
Asami, H.; Ishii, N.; Bentz, W.; Yazaki, K. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113 (Japan)] [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113 (Japan)
Dielectric Properties of Sulfopropyl Sephadex Gel Beads Dispersed in Aqueous Solutions
NASA Astrophysics Data System (ADS)
Dielectric measurements were carried out on beds consisting of beads of the ion-exchange resin sulfopropyl Sephadex of the strong-acid type over the frequency range 30 Hz to 130 MHz. Striking dielectric relaxations were observed with dielectric increments of 102-103 in dielectric units and relaxation frequencies of 10 MHz. The relative permittivities and electrical conductivities of ion-exchange resins with different ionic froms were evaluated by the method proposed in recent investigations on the basis of theories of interfacial polarization. The values of the relative permittivities thus determined were unchanged irrespective of the ionic form and were smaller than the value for water. The values of the electrical conductivities changed with the ionic species of the counter ions.
Ishikawa, Akira; Hanai, Tetsuya; Koizumi, Naokazu
Dielectric properties of water and their impact on the Earth's deep carbon cycle
NASA Astrophysics Data System (ADS)
Knowledge of the dielectric constant of water as a function of pressure (P) and temperature (T) plays a critical role in understanding the chemistry of aqueous systems, and in particular of fluids in the Earth's mantle. By using ab initio molecular dynamics, we computed the dielectric constant of water at T = 1000 and 2000 K, between 1 and 12 GPa, under conditions of the Earth's upper mantle. By comparing our results with available experimental data and empirical models, we discuss how the changes in the molecular dipole moments and hydrogen-bond network upon compression affect the dielectric constant of the liquid. Based on the calculated dielectric constants, the solubility products of carbonate minerals were predicted. At P ś 10 GPa and T = 1000 K, we found that MgCO3 (magnesite) is slightly soluble in water at the millimolal level, which suggests that water in the Earth's mantle has the capacity to store and transport significant quantities of oxidized carbon.
Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri; Galli, Giulia
Fabrication techniques and material properties of dielectric MgO thin filmsŚA status review
During the past few decades, considerable research effort has been directed towards the development of fundamental peculiarities of wide-gap (Eg>5eV) inorganic dielectric thin films. Wide-gap dielectrics are used for various technical and technological applications as laser materials, electronic components, radiation resistant materials, spectral transformers for luminescent lamps, detectors and dosimeters of several kind of radiations, various sensors and catalytic agents.
A. Moses Ezhil Raj; M. Jayachandran; C. Sanjeeviraja
Fundamental Properties of Organic Low-k Dielectrics Usable in the Cu Damascene Process
The material parameters for organic low-k dielectrics usable in the damascene process were studied using two different types of polymers with similar low dielectric constants, namely, the PQ-600 thermoplastic polymer and the SiLK thermosetting polymer. The resistibility of these polymers in the damascene process was investigated through hard-mask (SiO2) deposition, etching and chemical mechanical polishing (CMP) processes using scanning probe
Yutaka Nomura; Fumihiko Ota; Hiroyuki Kurino; Mitsumasa Koyanagi
Coupling between magnetism and dielectric properties in quantum paraelectric EuTiO3
The dielectric constant of quantum paraelectric EuTiO3, which contains Eu2+ with S=7\\/2 spin and Ti4+, has been measured under a magnetic field. The dielectric constant shows a critical decrease at the antiferromagnetic ordering of the Eu spins at 5.5 K, as well as a substantial change under a magnetic field (by ~7% with 1.5 T), indicating a strong coupling between
T. Katsufuji; H. Takagi
Realizing strain enhanced dielectric properties in BaTiO3 films by liquid phase assisted growth
NASA Astrophysics Data System (ADS)
The addition of a liquid-forming flux to barium titanate thin films promotes densification and grain growth, improves nonlinear dielectric properties, and allows residual strain to be sustained in polycrystalline films without cracking at thicknesses relevant to device fabrication. Relative tuning, an excellent indicator of crystalline quality and an important material property for tunable microwave devices, increases from 20% to 70%. Films exhibit 0.15% residual differential thermal expansion mismatch strain, resulting in a shift to the paraelectric-ferroelectric phase transition of 50 ░C. This result is in excellent agreement with theory, demonstrating the ability to tune ferroic transitions without epitaxial approaches.
Harris, David T.; Burch, Matthew J.; Ihlefeld, Jon F.; Lam, Peter G.; Li, Jing; Dickey, Elizabeth C.; Maria, Jon-Paul
Properties of autowaves including transitions between the traveling and static solitary states
NASA Astrophysics Data System (ADS)
An analytical investigation of shape, stability, and evolution of traveling and static solitary states-autosolitons (AS)-for the Rinzel-Keller-Koga-Kuramoto (RKKK) model of active media was carried out. The dependencies of the velocity and width of a traveling autosoliton on the bifurcation parameter at different ratios between characteristic lengths and times of activator and inhibitor were analyzed. It was shown that the traveling autosoliton loses stability at a velocity greater than those at which the corresponding solution disappears. It was found that the ASs velocity may become zero at some value of the bifurcation parameter, i.e., the traveling autosoliton transforms into a static one. At the same bifurcation point the static autosoliton loses stability with respect to the growth of fluctuations, which leads to the formation of a traveling or pulsating autosoliton. Transitions between traveling and static autosolitons are accompanied by hysteresis. It was also shown that besides this bifurcation point at certain parameters a ``tricritical point'' exists where the bifurcation of solutions in the form of traveling, static, and pulsating autosolitons is realized.
Kuznetsova, E. M.; Osipov, V. V.
NASA Astrophysics Data System (ADS)
We report on the tunable dielectric properties of Mg and Nb co-doped Ba0.45Sr0.55TiO3 (BST) thin film prepared by the magnetron sputtering using BST target (pure and doped with BaMg0.33Nb0.67O3 (BMN)) on Pt/TiO2/SiO2/Al2O3 4'' wafers at 700 ^oC under oxygen atmosphere. The electrical measurements are conducted on 2432 metal-ferroelectric-metal capacitors using Pt as the top and bottom electrode. The crystalline structure, microstructure, and surface morphology of the films are analyzed and correlated to the films dielectric properties. The BMN doped and undoped BST films have shown tunabilities of 48% and 52%; and leakage current densities of 2.2x10-6 A/cm^2 and 3.7x10-5 A/cm^2, respectively at 0.5 MV/cm bias field. The results indicate that the BMN doped film exhibits a lower leakage current with no significant decrease in tunability. Due to similar electronegativity and ionic radii, it was suggested that both Mg^2+ (accepter-type) and Nb^5+ (donor-type) dopants substitutTi^4+ ion in BST. The improvement in the film dielectric losses and leakage current with insignificant loss of tunability is attributed to the adversary effects of Mg^2+ and Nb^5+ in BST.
Alema, Fikadu; Reinholz, Aaron; Pokhodnya, Konstantin
Sulfonated polyurethane (PUI, matrix) is synthesized and composited with polyacene quinone radical polymers (PAQRs, filler). The polarization mechanism of these polymers and composites were investigated in terms of their frequency, temperature, and filler-concentration-dependent dielectric properties. We found that PUI/PAQR composites have a high permittivity, which is attributed to the filler-matrix interfacial polarization and the contact effect. The PAQR-concentration-dependent permittivity of different PUI/PAQR composites reveals a percolation threshold at 20-30 wt % with scaling exponents that indicate the intercluster polarization. The frequency dependence of dielectric response is well-fitted by using the Debye and Cole-Cole functions on the basis of the structural diagrams and equivalent circuit, leading to a detailed evaluation on heterogeneous structures of different PUI/PAQR composites. PMID:22324653
Zhu, Dan; Zhang, Juan; Bin, Yuezhen; Xu, Chunye; Shen, Jian; Matsuo, Masaru
Nanoparticles, which have multi-shell structure, are expected to be stable and high efficient for the light-emitting devices. The efficiency of luminescence is considered to be affected by the multi-shell structure. In order to understand the mechanism of high efficiency luminescence, it is necessary to evaluate the multi-shell structure and dielectric properties from each particle. High energy-resolution electron energy-loss spectroscopy (HR-EELS) based on TEM is a powerful tool for this purpose. By comparing between the experimental and the simulated results, it is possible to evaluate the effect of the size and physical property of each shell material on the dielectric properties of multi-shell nanoparticles. In this study, simulations of EELS spectra of multi-shell nanoparticle (core: CdSe, inner shell: CdS, outer shell: ZnS) and mono-shell nanoparticle (core: CdSe, shell: CdS) were conducted by the dielectric continuum theory[1].FigureĀ1 shows calculated EELS spectra of multi and mono shell nanoparticles. The spectra are calculated from dielectric functions of single CdSe, CdS and ZnS crystals, which were experimentally derived from HR-EELS spectra by using Kramers-Kronig analysis. The radius of 6.9 nm for the nanoparticle in the simulation corresponds to the average size of actual synthesized nanoparticles. Energy positions of arrows in the inset correspond to band gap energies of CdSe, CdS and ZnS[2]. In the spectrum of multi-shell nanoparticle, the intensity corresponding to interband transition near band gap of CdSe is suppressed comparing with that of the mono shell nanoparticle. This result indicates that ZnS outer shell affects the intensity profile of EELS spectrum near band gap. This effect should be sensitive for the thickness of the shells. Thus, there is a possibility that the effect of size and thickness of each core and shell on dielectric properties of multi-shell nanoparticles could be evaluated by using HR-EELS technique.jmicro;63/suppl_1/i18/DFU039F1F1DFU039F1Fig. 1.Calculated EELS spectra. PMID:25359810
Nakahigashi, Naoyuki; Sato, Yohei; Terauchi, Masami; Uehara, Masato
Dielectric and piezoelectric properties of the KNN ceramic compound doped with Li, La and Ta
NASA Astrophysics Data System (ADS)
With the purpose of improving the dielectric and piezoelectric properties of (K0.5Na0.5)NbO3 (KNN), a multiple doping strategy was tested in this research. Piezoceramics with composition [(K0.5Na0.5)0.94Li0.06]0.97La0.01(Nb0.9Ta0.1)O3 were prepared by the traditional ceramic method. The calcined powders were sintered in their own atmosphere at 1,100 ░C for 1.0, 1.5 and 2.5 h. X-ray diffraction analysis showed that the Li+, La3+ and Ta5+ cations diffuse into the KNN structure to form a perovskite-structured solid solution. For 1 h sintering time, a dominant orthorhombic phase is obtained, whereas for the longer times, the dominant phase was tetragonal. The presence of a tetragonal tungsten-bronze minority second phase is confirmed. Scanning electron micrographs show rectangular-shaped grains with a mean size of 1.1 ▒ 0.2 ?m. The existence of pores and traces of a liquid phase favoring grain growth and homogeneity is also observed. Experimental results show an enhancement of the permittivity associated with the enlargement of the c parameter of the cell that increases with sintering time. Li+ incorporation into the structure is made evident by its transition temperature at 400 ░C different from those of KNNLaTi (81-110 ░C) and KNNLaTa (340 ░C). An analysis of the phase transition of the samples indicates a normal rather than a diffuse transition. The electromechanical parameters k p, Q m, ? p, s 11, d 31 and g 31 are determined and compared to those of commercial PZT ceramics.
Fuentes, J.; Portelles, J.; Durruthy-RodrĒguez, M. D.; H'Mok, H.; Raymond, O.; Heiras, J.; Cruz, M. P.; Siqueiros, J. M.
Static and dynamic magnetic properties of UAs probed by muSR
Para- and antiferromagnetic UAs was studied by ?SR. Already 50 K above TN = 124 K the formation of a magnetic precursor phase is observed. In the type-I, 1k structure all field contributions from surrounding ordered uranium moments cancel on the average. The remaining very narrow (? 10 G wide) distribution of internal field is of static nature (1\\/? <
L. Asch; G. M. Kalvius; A. Kratzer; F. J. Litterst; A. Schenck; B. Hitti; F. N. Gygax; Ch. Scott; K. Mattenberger; O. Vogt
Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data
The goal of this project was to develop computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Solution of this problem was necessary for the quantification of uncertainty in future reservoir performance predictions and for the optimization of reservoir management.
Reynolds, Albert C.; Oliver, Dean S.; Zhang, Fengjun; Dong, Yannong; Skjervheim, Jan Arild; Liu, Ning
Mapping of Reservoir Properties and Facies Through Integration of Static and Dynamic Data
The goal of this project was to develop computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Solution of this problem is necessary for the quantification of uncertainty in future reservoir performance predictions and for the optimization of reservoir management.
Oliver, Dean S.; Reynolds, Albert C.; Zhang, Fengjun; Li, Ruijian; Abacioglu, Yafes; Dong, Yannong
Geometric properties of static Einstein-Maxwell dilaton horizons with a Liouville potential
We study nondegenerate and degenerate (extremal) Killing horizons of arbitrary geometry and topology within the Einstein-Maxwell-dilaton model with a Liouville potential (the EMdL model) in d-dimensional (d{>=}4) static space-times. Using Israel's description of a static space-time, we construct the EMdL equations and the space-time curvature invariants: the Ricci scalar, the square of the Ricci tensor, and the Kretschmann scalar. Assuming that space-time metric functions and the model fields are real analytic functions in the vicinity of a space-time horizon, we study the behavior of the space-time metric and the fields near the horizon and derive relations between the space-time curvature invariants calculated on the horizon and geometric invariants of the horizon surface. The derived relations generalize similar relations known for horizons of static four- and five-dimensional vacuum and four-dimensional electrovacuum space-times. Our analysis shows that all the extremal horizon surfaces are Einstein spaces. We present the necessary conditions for the existence of static extremal horizons within the EMdL model.
Abdolrahimi, Shohreh; Shoom, Andrey A. [Theoretical Physics Institute, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada)
Human effect elicited by static color slides was evaluated quantitatively using dimensional (N = 60 subjects) and differential or categorical (N = 57) self report, and facial electromyography (N = 20). Mean dimensional self reports of affective responses were highly replicable across cohorts. Mean categorical response profiles over seven affective categories were monomodal for some slides, but multimodal for most,
W. Jackson Davis; Matthew A. Rahman; Libby J. Smith; Ayesha Burns; Laura Senecal; Douglas McArthur; Jennifer A. Halpern; Aaron Perlmutter; Wendy Sickels; Wendelin Wagner
Application of the Brewster angle to quantify the dielectric properties of ground ice formations
NASA Astrophysics Data System (ADS)
Previous studies of ground ice using moveout type ground-penetrating radar (GPR) surveys indicate that the dielectric permittivity can constrain the type of ground ice present in the subsurface. Due to the high-loss nature of the active layer over permafrost targets, however, the signal strength of GPR signals is often insufficient to resolve the basal boundary required for determining the dielectric permittivity of an underlying unit. We apply a non-conventional antenna orientation and post-processing method to determine the dielectric permittivity of the unit underlying the lowest resolvable boundary. We conduct moveout surveys using a 450 MHz GPR with collinear parallel oriented antennas on two adjacent ground ice formations in the region of Thomas Lee Inlet, Devon Island, Nunavut. We exploit the Brewster angle to calculate the approximate dielectric permittivity of ground ice formations below the active layer. The results agree within 1 dielectric unit with on-ice permittivity measurements made during a complementary study of the site.
Thomson, Laura I.; Osinski, Gordon R.; Pollard, Wayne H.
NASA Astrophysics Data System (ADS)
We perform an ab initio molecular dynamics study of the static, dynamic and electronic properties of the liquid Bi-Pb alloy at three concentrations, including the eutectic one. This alloy is of particular technological interest for its possible use as coolant in fast reactors. Our predictions are in good agreement with the available experimental data. In particular, the computed total static structure factors reproduce accurately the neutron diffraction results, and the predicted adiabatic sound velocity and shear viscosity compare well with the experimental values. The partial dynamic structure factors exhibit clear side peaks indicative of propagating density fluctuations, and the longitudinal and transverse dispersion relations show several branches.The electronic density of states show that the liquid Bi-Pb alloy is a good metal, but with strong deviations from the free-electron parabolic curve.
Souto, J.; Alemany, M. M. G.; Gallego, L. J.; Gonzalez, L. E.; Gonzalez, D. J.
Structural and dielectric properties of undoped ZnO pellets prepared by solid state route
NASA Astrophysics Data System (ADS)
Undoped zinc oxide has been prepared at various growth temperatures by a conventional sintering process. The crystal structures of the prepared samples were studied by X-ray diffraction. The frequency-dependent dielectric dispersion of all the sintered ZnO ceramics was investigated in the temperature range from -100 to 30 ░C and in the frequency range from 1 Hz to 10 MHz by broadband dielectric spectroscopy. An analysis of the complex permittivity and electric modulus as a function of frequency has been performed assuming a distribution of relaxation times. The pellet sintered at 900 ░C showed the lowest value of the dielectric strength. The temperature dependent of the parameter ? is discussed. While the charge transport through the grain and grain boundary regions was examined by impedance spectroscopy. Activation energy values extracted from conduction measurements were found to be in the range of 0.09 and 0.3 eV.
Chaari, Mariem; Matoussi, Adel
NASA Astrophysics Data System (ADS)
To develop ceramic capacitors with a high effective dielectric constant, we attempted to fabricate BaTiO3 (BT) complexes with embedded Ag nanoparticles by wet chemical processes. Ag nanoparticle-adsorbed dendritic BT particles, Ag-BT hybrid particles, were synthesized from the sol-gel-derived precursor gel powders containing Ag, Ba, and Ti by hydrothermal treatment. These particles were pressed with BT fillers and TiO2 precursor nanoparticles into green compacts, and then, the green compacts were chemically converted into the Ag/BT nanocomplex compacts in Ba(OH)2 aqueous solution under the hydrothermal condition at 160 ░C. The effective dielectric constant of the resultant Ag/BT nanocomplexes increases with an increase in Ag content. The maximal effective dielectric constant of approximately 900 was recorded for the nanocomplex with the Ag content of 10.7 vol %.
Ueno, Shintaro; Sakamoto, Yasunao; Nakashima, Kouichi; Wada, Satoshi
Synthesis of monodisperse TiO2-paraffin core-shell nanoparticles for improved dielectric properties.
Core-shell structures of oxide nanoparticles having a high dielectric constant, and organic shells with large breakdown field are attractive candidates for large electrical energy storage applications. A high growth temperature, however, is required to obtain the dielectric oxide nanoparticles, which affects the process of core-shell formation and also leads to poor control of size, shape, and size-distribution. In this communication, we report a new synthetic process to grow core-shell nanoparticles by means of an experimental method that can be easily adapted to synthesize core-shell structures from a variety of inorganic-organic or inorganic-inorganic materials. Monodisperse and spherical TiO2 nanoparticles were produced at room temperature as a collimated cluster beam in the gas phase using a cluster-deposition source and subsequently coated with uniform paraffin nanoshells using in situ thermal evaporation, prior to deposition on substrates for further characterization and device processing. The paraffin nanoshells prevent the TiO2 nanoparticles from contacting each other and also act as a matrix in which the volume fraction of TiO2 nanoparticles was varied by controlling the thickness of the nanoshells. Parallel-plate capacitors were fabricated using dielectric core-shell nanoparticles having different shell thicknesses. With respect to the bulk paraffin, the effective dielectric constant of TiO2-paraffin core-shell nanoparticles is greatly enhanced with a decrease in the shell thickness. The capacitors show a minimum dielectric dispersion and low dielectric losses in the frequency range of 100 Hz-1 MHz, which are highly desirable for exploiting these core-shell nanoparticles for potential applications. PMID:20359188
Balasubramanian, Balamurugan; Kraemer, Kristin L; Reding, Nicholas A; Skomski, Ralph; Ducharme, Stephen; Sellmyer, David J
NASA Astrophysics Data System (ADS)
In this work, we have determined the dielectric and conductance properties of multi-wall carbon nano-tubes (MWCNT) in polyvinylidene fluoride (PVDF) nanocomposite thin films as a function of temperature and frequency. Samples, ranging from 15 - 280 microns in thickness, were measured in the temperature range from 21 to 90░C and in frequencies from 50Hz to 110MHz. The samples were prepared by the solution casting technique. Measures indicate that at constant temperatures, the real dielectric constant decreases at lower frequencies, stays steady at low frequencies but rise at higher frequencies over towards the strong resonance. The dielectric loss, a particular concern as it is inversely related to the conductance, decreases also at lower frequencies but rise at higher frequencies with a steeper slope in each case. Additionally, we have measured the pyroelectric coefficient in the same temperature range, compared the pyroelectric coefficient results with previous measures made on silver nanoparticle in PVDF thin films and provided preliminary evidence of the causative microscopic response mechanism. Our MWCNT:PVDF thin films yield higher figures of merit than that indicated by pure PVDF thin films and results indicate a usage of MWCNT:PVDF thin films in infrared uncooled sensors and vidicon technology.
Edwards, Matthew; Guggilla, Padmaja; Corda, John; Egarievwe, Stephen
NASA Astrophysics Data System (ADS)
M-type hexaferrite BaCr x Ga x Fe12-2 x O19 ( x = 0.2) powders have been synthesized by use of a sol-gel autocombustion method. The powder samples were pressed into 12-mm-diameter pellets by cold isostatic pressing at 2000 bar then heat treated at 700░C, 800░C, 900░C, and 1000░C. X-ray diffraction patterns of the powder sample heat treated at 1000░C confirmed formation of the pure M-type hexaferrite phase. The electrical resistivity at room temperature was significantly enhanced by increasing the temperature of heat treatment and approached 5.84 ū 109 ? cm for the sample heat treated at 1000░C. Dielectric constant and dielectric loss tangent decreased whereas conductivity increased with increasing applied field frequency in the range 1 MHz-3 GHz. The dielectric properties and ac conductivity were explained on the basis of space charge polarization in accordance with the Maxwell-Wagner two-layer model and Koop's phenomenological theory. The single-phase synthesized materials may be useful for high-frequency applications, for example reduction of eddy current losses and radar absorbing waves.
Ali, Ihsan; Islam, M. U.; Awan, M. S.; Ahmad, Mukhtar
The thermophysical, dielectric and electro-optic properties of polymer-dispersed liquid crystal (PDLC) films made of monodisperse polystyrene (PS) and 4-n-pentyl-4(')-cyanobiphenyl (5CB) are investigated by polarized optical microscopy, differential scanning calorimetry, ac impedance analysis, and forward transmittance measurement technique. The PS-5CB system exhibits an upper critical solution temperature (UCST) shape phase diagram with a wide isotropic+isotropic (I+I) miscibility gap between the isotropic and nematic+isotropic (N+I) regions. An absorption domain in the dielectric spectrum of PDLC films was clearly observed at low frequency, and unambiguously assigned to the confined liquid crystalline phase in both nematic and isotropic states. The correlation between the dielectric and electro-optical results for PS-5CB (30:70) samples has shown that in the vicinity of the low frequency absorption domain ( approximately 200 Hz at T=25 degrees C), a drastic decrease in the optical transmittance of the film occurs. This phenomenon can be related to an interfacial polarization process resulting from a charge accumulation at the droplet-polymer interface (Maxwell-Wagner-Sillars effect). PMID:15089305
Boussoualem, Mourad; Roussel, Frķdķrick; Ismaili, Mimoun
NASA Astrophysics Data System (ADS)
Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle size distribution were obtained as the concentration ratio of iron ions to carboxylic acid groups decreased. The Fe nanoparticles were subsequently coated with silica (SiO2) layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporating Fe@SiO2 nanoparticles with polydimethylsiloxane (PDMS) elastomers. Experimental results showed that the dielectric permittivity (?) and magnetic permeability (?) of the polymer composite increased with increasing amount of Fe@SiO2 nanoparticle doping. The dielectric loss (tan?) was near 0.020 at a frequency of 1 GHz.
Yang, T. I.; Brown, R. N. C.; Kempel, L. C.; Kofinas, P.
Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle size distribution were obtained as the concentration ratio of iron ions to carboxylic acid groups decreased. The Fe nanoparticles were subsequently coated with silica (SiO(2)) layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporating Fe@SiO(2) nanoparticles with polydimethylsiloxane (PDMS) elastomers. Experimental results showed that the dielectric permittivity (?) and magnetic permeability (?) of the polymer composite increased with increasing amount of Fe@SiO(2) nanoparticle doping. The dielectric loss (tan?) was near 0.020 at a frequency of 1 GHz. PMID:21289404
Yang, T I; Brown, R N C; Kempel, L C; Kofinas, P
Thermal and dielectric properties of gel-grown cobalt malonate dihydrate single crystals
NASA Astrophysics Data System (ADS)
Single crystals of cobalt malonate dihydrate were grown in a silica gel medium by the single diffusion method. The thermal behavior of the crystals was investigated by thermogravimetric and differential thermal analyses. The dielectric constant, dielectric loss and ac conductivity of the crystals were estimated as a function of temperature in the range 40-140 ░C for four different frequencies. The results indicate that the grown crystals are thermally stable up to about 150 ░C and exhibit a phase transition at 130 ░C.
Mathew, Varghese; Xavier, Lizymol; Mahadevan, C. K.; Abraham, K. E.
Dielectric Properties of Nanoporous Metal-Organic Framework Materials in the Millimeter-Wave Band
NASA Astrophysics Data System (ADS)
Complex dielectric permittivity of eight nanoporous metal-organic frameworks (MOFs) is measured for the first time in the short-wavelength region of the millimeter-wave band. The measurements show that these nanoporous materials exhibit either a Debye-type or a damped resonance dispersion. It is established that the dielectric characteristics of the MOFs are significantly changed when the materials are placed in a humid environment. This fact can be used to design sensors to monitor the composition of the surrounding atmosphere.
Meriakri, V. V.; Nikitin, I. P.; Parkhomenko, M. P.; Fedoseev, N. A.; Lu, Kuang-Lieh
Evaluation of absorptive properties and permeability of thin sheet magneto-dielectric materials
NASA Astrophysics Data System (ADS)
An analytical model to evaluate attenuation on the coaxial line with the central conductor coated with a magneto-dielectric layer is proposed and validated by the experiments and numerical modeling. This model is convenient for comparing absorptive effectiveness of different materials, as well as of different thicknesses and lengths of the same material. The proposed model also lays the basis for the technique to extract permeability of thin sheet magneto-dielectric materials by wrapping them around a central conductor of the coaxial airline.
Koledintseva, Marina Y.; Khilkevich, Victor V.; Razmadze, Alexander G.; Gafarov, Aleksandr G.; De, Soumya; Drewniak, James L.
Epitaxial behavior of (Pb,Sr)TiO3 thin films on (110) NdGaO3 substrates fabricated in different conditions have been investigated using high resolution x-ray diffraction and characterized with interdigital dielectric measurement. A slow cooling results in films with a-axis normal to the surface (a-axis growth), whereas a fast cooling leads to growth of c-axis oriented films. The dielectric properties of the films prepared
Y. Lin; X. Chen; S. W. Liu; C. L. Chen; Jang-Sik Lee; Y. Li; Q. X. Jia; A. Bhalla
Elastic, piezoelectric, and dielectric properties of 0.58Pb,,Mg13Nb23...O3-0.42PbTiO3 single crystal
Elastic, piezoelectric, and dielectric properties of 0.58Pb,,Mg1├?3Nb2├?3...O3-0.42PbTiO3 single February 2004 The elastic, piezoelectric, and dielectric constants of 0.58Pb Mg1/3Nb2/3)O3-0.42PbTiO3 PMN temperature the PMN-42%PT single crystal has tetragonal symmetry. The measured piezoelectric constant d33
Elastic, piezoelectric, and dielectric properties of multidomain 0.67Pb,,Mg1├?3Nb2├?3...O3 ┬Ł0.33Pb for publication 11 June 2001 The elastic, piezoelectric, and dielectric constants of 0.67Pb Mg1/3Nb2/3 O3┬Ł0.33Pb k33 94% and piezoelectric constant d33 2800 pC/N if the poling is done along the 001 of pseudocubic
Cao, Wenwu
The dielectric constant of the quantum paraelectric EuTiO3 exhibits a sharp decrease at about 5.5 K, at which temperature antiferromagnetic ordering of the Eu spins simultaneously appears, indicating coupling between the magnetism and dielectric properties. The transverse-field Ising model and Heisenberg model are successfully applied to EuTiO3 electrical and magnetic subsystems, respectively. By adding an appropriate coupling term between the
H. Wu; Q. Jiang; W. Z. Shen
The solvothermal reactions of BiI(3), KI, I(2), 4,4'-bipyridine (4,4'-bipy), and a small amount of water in alcohol and acetonitrile produced four bipyridinium iodobismuthates {[MQ](3)[Bi(2)I(6)(?-I)(3)][Bi(2)I(6)(?-I)(2)(MQ)(2)](3)} (1, MQ(+) = N-methyl-4,4'-bipyridinium), {[EQ](3)[Bi(2)I(6)(?-I)(3)][Bi(2)I(6)(?-I)(2)(EQ)(2)](3)} (2, EQ(+) = N-ethyl-4,4'-bipyridinium), [MV][BiI(5)] (Eur. J. Inorg. Chem., 2010, 5326) (3, MV(2+) = N,N'-dimethyl-4,4'-bipyridinium), and [EV](2)[Bi(4)I(10)(?-I)(4)(?(3)-I)(2)] (4, EV(2+) = N,N'-diethyl-4,4'-bipyridinium). In these reactions, 4,4'-bipy was partly or completely alkylated by alkyl groups generated from the cleavage of C-O bond of alcohols, forming the N-alkyl-4,4'-bipyridinium cation (Q(+)) and the N,N'-dialkyl-4,4'-bipyridinium dication (V(2+)), respectively. Compounds 1-4 were characterized by elemental analysis, IR, (1)H NMR and single-crystal X-ray diffraction analysis. The optical, electrical conductive and dielectric properties of these compounds were investigated. The dielectric constants of the Q(+)-based compounds were larger than the values of the V(2+)-based ones, which showed that the weak electrostatic interactions in the structures may benefit the polarizability of molecules, thereby resulting in a larger dielectric response of the structures under an external electric field, while the strong electrostatic interactions between the positive and negative charge units would lead to a low dielectric constant (low-k) behavior of these compounds. PMID:21311791
Chen, Yang; Yang, Zhou; Wu, Xin-Yi; Ni, Chun-Yan; Ren, Zhi-Gang; Wang, Hui-Fang; Lang, Jian-Ping
Quasi-static and dynamic mechanical properties of a granite and a sandstone
The quasi-static failure criteria, elastic constants, and p-wave velocities have been determined for a granite and a sandstone in which blasting experiments are being carried out by the Advanced Technology Division (6258). In addition, the dynamic strength of the granite was measured using a Kolsky bar. Both rocks show a linear increase in strength with increasing confining pressure. The dynamic strength of the granite is as much as 330% greater than the quasi-static value. The strength of the granite was also dependent on the angle between the foliation and the loading direction. There was a 20% difference in the p-wave velocity between that measured parallel to and perpendicular to the bedding in the sandstone. 4 refs., 4 figs., 5 tabs.
Olsson, W.A.
NASA Astrophysics Data System (ADS)
Bulk dc resistivity and dielectric constant measurements at different temperatures and frequencies have been performed in LaMn1-xFexO3 (0 <= x <= 1.0) as a result of Fe substitution both for as-synthesized and oxygen annealed samples. Temperature dependence of the real part of the dielectric constant at different frequencies show a frequency and temperature independent value (epsilonS) at low temperature for x >= 0.15 where epsilonS rises with x reaching a maximum at x = 0.5 and then decreases sharply at x = 0.70 showing a further increasing trend with a further increase in x. The sharp drop of epsilonS at x = 0.70 is correlated with the structural change from rhombohedral to the orthorhombic structure. A considerable increase in epsilonS ~ 43% is observed for an increase in x from 0.15 to 0.50. Furthermore, epsilonS is increased considerably (up to ~17% at x = 0.5) due to the oxygen annealing for x <= 0.50. The low temperature resistivities satisfying the variable range hopping model are found to be related to the increase in epsilonS with x for x <= 0.50. The analysis of the complex impedance and modulus (M) planes at low temperature indicates electrical inhomogeneities in the grain interior of the compounds where the capacitance obtained from the high-frequency complex-M arc shows an anomaly at the onset of the short range ferromagnetic ordering, suggesting a possible magnetoelectric coupling for x = 0.3.
Karmakar, A.; Majumdar, S.; Singh, A. K.; Giri, S.
ZnTiO3 powders and borosilicate glass were made by sol¢gel method, and then mixed for co-firing at low temperatures. The results show that the borosilicate glass was liquefied to improve the density of the ceramic during sintering. However, Zn4O(BO2)6 and TiO2 were formed if too much borosilicate glass was added (over 10wt.%). The microwave dielectric properties of the ZnTiO3 co-fired with
Yin-Lai Chai; Yee-Shin Chang; Yu-Jen Hsiao; Yu-Chan Lian
Effects of additives on the sintering temperature and dielectric properties of ZnTiO 3 based ceramic
The effects of various additives, namely ZnO¢B2O3¢SiO2 (ZSB), B2O3 and B2O3+LiF on the lowering of sintering temperature and dielectric properties of ZnTiO3 based ceramics were investigated. From the dilatometric studies, it was shown that the sintering temperature is significantly lowered owing to the addition of 15mol.% of ZSB or of the addition of 15mol.% of B2O3: ZSB added sample can
A. Chaouchi; M. Aliouat; S. Marinel; S. dÆAstorg; H. Bourahla
V2O5-doped zinc titanate ceramics (ZnTiO3) were prepared by conventional mixed-oxide method combined with a semi-chemical processing. The effects of V2O5 addition on the phase-structures and the dielectric properties of ZnTiO3 ceramics were investigated. The results show the sintering temperature of zinc titanate ceramics could be lowered from 1,150\\u000a to 930 ░C by reducing the size of starting powders using a
Xiangchun Liu; Feng Gao; Lili Zhao; Ming Zhao; Changsheng Tian
The growth of single-crystals of Pb-K-Niobate and temperature dependence of dielectric property
by TSSG method VII. Results of dielectric measurement of PKN single crystals as a function of x. Page 28 34 36 57 72 LIST OF FIGURES Figure 1. First order transition. . 2. Second order transition. Binary phase diagrams. (a) components... for the fabrication of temperature-compensated SAW devices due to its high piezoelectric[2) and electromechanical properties[3). Such devices require large, crack-free single crystals of PKN, which are very difficult to synthesize. For lack of device quality single-crystals...
Islam, Faizul
The piezoelectric and dielectric properties of Cd additive Sm-modified PbTiO 3 ceramics
Effects of cadmium dopants on the piezoelectric and dielectric properties of Sm-modified PbTiO3 ceramics have been investigated. Sm-modified lead PbTiO3 ceramics with a composition of (Pb0.85?xCdxSm0.1)(Ti0.98Mn0.02)O3, x=0.01¢0.08 were prepared by conventional mixed-oxide methods with sintering temperature at 1150░C. We successfully showed that Cd additive is helpful to grow the grain size and obtain much higher thickness electromechanical coupling coefficient, kt
Te-Yi Chen; Sheng-Yuan Chu; Shih-Jeh Wu; Yung-Der Juang
Effect of calcium on the piezoelectric and dielectric properties of Sm-modified PbTiO 3 ceramics
In this paper, effects of calcium dopants on the piezoelectric and dielectric properties of Sm-modified lead titanate (PbTiO3) ceramics have been investigated. Sm-modified PbTiO3 ceramics with a composition of (Pb0.88?xCaxSm0.08)(Ti0.98Mn0.02)O3; x=0.11¢0.17 were prepared by conventional mixed-oxide methods with sintering temperature at 1200░C. We successfully showed that Ca additive is helpful to obtain much higher thickness electromechanical coupling coefficient, kt (>0.57),
Sheng-Yuan Chu; Chia-Hsin Chen
High-temperature dielectric properties of incipient ferroelectric Gd0.5Na0.5TiO3
NASA Astrophysics Data System (ADS)
Gd0.5Na0.5TiO3 ceramic samples were prepared by the solid-state reaction method. Incipient ferroelectricity was confirmed in the sample. Dielectric properties were investigated at temperatures from room temperature to 1073 K and the frequency range of 20 Hz-10 MHz. By means of electric modulus and impedance analysis, the sample was found to show two thermally activated relaxations with the high-frequency (low-temperature) one being the relaxation caused by hopping motion of oxygen vacancies and the low-frequency (high-temperature) one being the interfacial relaxation.
Wang, Chunchang; Wang, Jing; Sun, Xiaohong; Li, Qiuju; Zhang, Jian; Zheng, Jun; Cheng, Chao
Using first principles calculations based on density functional theory and a coupled finite-fields/finite-differences approach, we study the dielectric properties, phonon dispersions and Raman spectra of ZnO, a material whose internal polarization fields require special treatment to correctly reproduce the ground state electronic structure and the coupling with external fields. Our results are in excellent agreement with existing experimental measurements and provide an essential reference for the characterization of crystallinity, composition, piezo- and thermo-electricity of the plethora of ZnO-derived nanostructured materials used in optoelectronics and sensor devices. PMID:24141391
Calzolari, Arrigo; Nardelli, Marco Buongiorno
Dielectric properties and thermal destruction of poly(dimethylsiloxane)/Fe2O3/SiO2 nanocomposites
NASA Astrophysics Data System (ADS)
Thermally stimulated chemical transformation of poly(dimethilsiloxane) (PDMS) adsorbed onto highly disperse Fe2O3/SiO2 was studied using FTIR, thermogravimetry and differential thermal analysis. The influence of active surface sites on this transformation was investigated since iron oxide affects the degradation of PDMS. It was shown that PDMS provides stable (in the 100-500 ░C range) hydrophobic properties to Si?2/PDMS depending on PDMS concentration. Differential scanning calorimetry, thermally stimulated depolarization currents and dielectric relaxation spectroscopy techniques were employed to investigate the effects of iron oxide on thermal transitions (in particular glass transition), segmental dynamics and interfacial interactions in PDMS/oxides nanocomposites.
Galaburda, M. V.; Klonos, P.; Gun'ko, V. M.; Bogatyrov, V. M.; Borysenko, M. V.; Pissis, P.
In this research, the effects of pre-fatigue on the dynamic and quasi-static tensile properties of laser welded butt joints between three kinds of steel plates, i.e. HR270, HR590 and HR780 steels, were investigated using tensile split Hopkinson bar apparatus. There were no significant effects of pre-fatigue on the dynamic and static tensile properties of HR780-HR270 and HR780-HR590 joints. Their fracture
H. Kobayashi; M. Daimaruya; H. Tsuda; K. Horikawa; Y. Yamada
Dielectric properties of fully hydrated nucleotides in the terahertz frequency range.
We use terahertz time domain spectroscopy (THz-TDS) to determine the complex frequency-dependent dielectric response of all four nucleotides at different dilute concentrations. In addition, the suspension model's ability to extract the dielectric response of just the nucleotide with the hydration shell epsilon(b) excluding the dielectric information relating to the bulk will be verified. The suspension model enables us to make the determination that the nucleotides have influences on the water molecules out to the fourth hydration shell. We use a two Debye relaxation fit model for water, all concentrations and all epsilon(b) values. We observed how the nucleotides affect the relaxation parameters in relation to that of pure bulk water. With this information, we notice a transition between purines and pyrimidines, where one is a hydrogen-bond network structure building type material with a low concentration increment and the other is a structure breaking type material with a low concentration decrement. Due to conductivity measurements, we determine that kinetic depolarization is a negligible affect compared to that of dielectric saturation, which we find to dominate where a decrement is found. PMID:20590216
Glancy, P; Beyermann, W P
Apparatus for the Study of the Dielectric Properties of Macromolecular Solutions under Flow
Some solutions show a change in value of their dielectric constant and specific conductance when subjected to shearing stresses produced by a velocity gradient established within them. A detailed account is given of an apparatus which has been used for studying this effect. The solution to be investigated is placed in the annular space between two concentric cylinders. The gap
H. G. Jerrard; T. A. Fisher; B. A. W. Simmons
Double doping effect on the structural and dielectric properties of PZT ceramics
NASA Astrophysics Data System (ADS)
Polycrystalline samples of the modified Pb(Zr1-x Tix)O3 (PZT) composition, with representative formula Pb0.92(LazBi1-z)0.08(Zr0.65Ti0.35)0.98O3 (PLBZT), a family of relaxor ferroelectrics, were prepared via the chemical route with z = 0.3, 0.6 and 0.9. Crystalline phases of powders calcined at different temperatures and the microstructure of the sintered pellets were investigated by x-ray diffraction (XRD) analysis and scanning electron microscopy, respectively. XRD confirms the result obtained by differential scanning calorimetry. The XRD profile shows that the samples having z = 0.9 and 0.6 do not exhibit a pyrochlore phase, whereas the samples with z = 0.3, have 3% of the pyrochlore phase. Microstructural analysis suggests that the shape of grains and intergranular residual pores are modified upon La doping. The dielectric constant and dielectric losses were measured as a function of frequency at room temperature for different frequencies starting from 0.1 kHz to 1 MHz. The dielectric constant was found to be strongly influenced by frequency whereas the Curie temperature remained almost the same. Finally, we conclude that the dielectric constant, loss and activation energy of PLBZT strongly suggest that these compounds are suitable for the preparation of high value capacitors and may be good candidates for device applications.
Goel, Puja; Yadav, K. L.; James, A. R.
Properties of atomic layer deposited dielectrics for AlGaN/GaN device passivation
NASA Astrophysics Data System (ADS)
In order to minimize ac-dc dispersion, reduce gate leakage and maximize ac transconductance, there is a critical need to identify optimal interfaces, low-k passivation dielectrics and high-k gate dielectrics. In this paper, an investigation of different atomic layer deposited (ALD) passivation dielectrics on AlGaN/GaN-based hetero-junction field effect transistors (HFETs) was performed. Angle-resolved x-ray photoelectron spectroscopy revealed that HCl/HF and NH4OH cleans resulted in a reduction of native oxide and carbon levels at the GaN surface. The role of high temperature anneals, following the ALD, on the effectiveness of passivation was also explored. Gate-lag measurements on HFETs passivated with a thin ALD high-k Al2O3 or HfAlO layer capped with a thick plasma enhanced chemical vapor deposited (PECVD) low-k SiO2 layer, annealed at 600-700 ░C, were found to be as good as or even better than those with conventional PECVD silicon nitride passivation. Further, it was observed that different passivation dielectric stacks required different anneal temperatures for improved gate-lag behavior compared to the as-deposited case.
Ramanan, Narayanan; Lee, Bongmook; Kirkpatrick, Casey; Suri, Rahul; Misra, Veena
Nonlinear dielectric properties of planar structures based on ferroelectric betaine phosphite films
NASA Astrophysics Data System (ADS)
Ferroelectric films of partly deuterated betaine phosphite are grown on NdGaO3(001) substrates with an interdigitated system of electrodes on their surfaces by evaporation at room temperature. These films have a high capacitance in the ferroelectric phase transition range. The dielectric nonlinearity of the grown structures is studied in small-signal and strong-signal response modes and in the intermediate region between these two modes by measuring the capacitance in a dc bias field, dielectric hysteresis loops, and the Fourier spectra of an output signal in the Sawyer-Tower circuit. In the phase transition range, the capacitance control ratio at a bias voltage U bias = 40 V is K ? 7. The dielectric nonlinearity of the structures in the paraelectric phase is described by the Landau theory of second-order phase transitions. The additional contribution to the nonlinearity in the ferroelectric phase is related to the motion of domain walls and manifests itself when the input signal amplitude is higher than U st ś 0.7-1.0 V. The relaxation times of domain walls are determined from an analysis of the frequency dependences of the dielectric hysteresis.
Balashova, E. V.; Krichevtsov, B. B.; Svinarev, F. B.; Yurko, E. I.
The dielectric properties of soil-water mixtures at microwave frequencies
NASA Technical Reports Server (NTRS)
Recent measurements on the dielectric constants of soil-water mixtures show the existence of two frequency regions in which the dielectric behavior of these mixtures was quite different. At the frequencies of 1.4 GHz to 5 GHz, there were strong evidences that the variations of the dielectric (epsilon) with water content (W) depended on soil type. While the real part of epsilon for sandy soils rose rapidly with the increase in W, epsilon for the high-clay content soils rose only slowly with W. As a consequence, epsilon was generally higher for the sandy soils than for the high-clay content soils at a given W. On the other hand, most of the measurements at frequencies 1 GHz indicated the increase of epsilon with W independent of soil types. At a given W, epsilon' (sandy soil) approximately equals epsilon (high-clay content soil) within the precision of the measurements. These observational features can be satisfactorily interpreted in terms of a simple dielectric relaxation model, with an appropriate choice of the mean relaxation frequency f(m) and the range of the activation energy (beta). It was found that smaller f(m) and larger beta were required for the high-clay content soils than the sandy soils in order to be consistent with the measured data.
Wang, J. R.
On the properties of dielectric elastomer actuators and their design implications
Dielectric elastomer actuators (DEA) have been studied extensively under laboratory conditions where they have shown promising performance. However, in practical applications, they have not achieved their full potential. Here, the results of detailed analytical and experimental studies of the failure modes and performance boundaries of DEAs are codified into design principles for these actuators. Analysis shows that the performance of
J.-S. Plante; S. Dubowsky
On the Properties of Dielectric Elastomer Actuators and Its Implications for Their Design
Dielectric Elastomer Actuators (DEA) have been studied extensively under laboratory conditions where they have shown promising performance. However, in practical applications, they have not achieved their full potential. Here the results of detailed analytical and experimental studies of the failure modes and performance boundaries of DEAs are codified into design principles for these actuators. Analysis shows that the performance of
J.-S. Plante; S. Dubowsky
NASA Astrophysics Data System (ADS)
In order to enhance the permittivity and tunability of the dielectric component, a thin film dielectric composite consisting of a radio frequency sputtered SrTiO3 (STO) buffer layer and metalorganic solution deposited Mg-doped BaxSr1-xTiO3 (Mg-BST) thin film overgrowth was developed using affordable industry standard processes and materials. The effect of the STO buffer layer thickness on the dielectric response of the heterostructure was investigated. Our results demonstrate that the composite film heterostructure, evaluated in the metal-insulator-metal configuration Pt/STO/Mg-BST/Pt on sapphire substrate, with the thinner (9-17 nm) STO buffer layers possessed enhanced permittivity (?r ś 491) with respect to the thicker 41 nm buffer layer (?r ś 360) and that of a control Mg-BST film without a STO buffer layer (?r ś 380). Additionally, the composite film with the thinner buffer layers were shown to have low losses (tan ? ś 0.02), low leakage characteristics (J = 7.0 ū 10-9 A/cm2), high breakdown voltage (VBR > 10 V), a large grain microstructure (ś125 nm), and smooth pin-hole free surfaces. The enhanced permittivity of the composite dielectric film resulted from three major factors: (i) the template-effect of the thin STO buffer layer on the thicker Mg-BST over-layer film to achieve a large grain microstructure, (ii) the low viscosity of the metallo-organic solution deposition (MOSD) solution, which ensured heterogeneous nucleation of the Mg-BST overgrowth film on the surface of the STO buffer layer, and (iii) minimization of the low permittivity grain boundary phase (TiO2-x phase). The dielectric response of the BST can be explained using a thermodynamic model taking into account interlayer electrostatic and electromechanical interactions. Additionally, Mg doping of the BST enabled low loss and low leakage characteristics of the heterostructure. The large permittivity, low loss, low leakage characteristics, and defect free surfaces of the composite dielectric heterostructure promote tunable device miniaturization and hold the potential to enable enhanced electromagnetic coupling in ferromagnetic/high permittivity dielectric heterostructures, which in turn would facilitate the realization of integrated charge mediated voltage controlled magnetic radio frequency/microwave communication devices.
Cole, M. W.; Ngo, E.; Hubbard, C.; Hirsch, S. G.; Ivill, M.; Sarney, W. L.; Zhang, J.; Alpay, S. P.
New Cu?TeO? ceramics: phase formation and dielectric properties.
Targeting low temperature cofired ceramics (LTCC) applications and base-metal electrode multilayer ceramic capacitors (BME-MLCCs), ceramics of a new composition, tricopper tellurate (Cu3TeO6), are reported here. The crystal structure of Cu3TeO6 was determined to be cubic, Ia3, with the unit cell parameter a = 9.538 ┼. The sequence of phase formation is proposed with the oxidation of tetravalent tellurium (Te(4+)) into hexavalent tellurium (Te(6+)) as a key step for the formation of Cu3TeO6. Ceramics sintered at 865 ░C with densities of 94% exhibit two dielectric anomalies in the temperature dependence of the dielectric response, around -150 ░C and +50 ░C, respectively, accompanied by obvious frequency dispersion of the relative permittivity (?(r)) and dielectric losses (tan ?), with an Arrhenius like behavior. A temperature stable dielectric region (near room temperature) formed between the two anomalies with ?(r) ? 12 and tan ? ? 0.01, and a very low positive temperature coefficient of the relative permittivity (TC?(r)), 2.07 ū 10(-4) ░C(-1), was obtained in the same region. The low temperature dielectric anomaly is associated with the possible mixed Cu(+)/Cu(2+) valence in Cu3TeO6 ceramics, while the high temperature anomaly is attributed to point defect ordering, including VO, CuCu2+(+)', which might be formed during sintering. Therefore, Cu3TeO6 ceramics are of interest in view of not only the possible applications in BME-MLCCs, LTCC, and related technologies, but also for their possible compatibility with low cost abundant Cu electrodes. PMID:24960531
Zhu, Xiaoli; Wang, Zhonghua; Su, Xinming; Vilarinho, Paula M
NASA Astrophysics Data System (ADS)
Magnetic nanoparticles of chromium substituted cobalt ferrite (CoFe2-xCrxO4) were prepared by the co-precipitation method for different concentrations (x=0.0, 0.1, 0.2 and 0.3) of chromium (Cr) and were annealed at 600 ░C for 3 h. Formation of single phase cubic spinel structure was confirmed by X-ray diffraction analysis and the average crystallite size was in the range of 15-23 nm. Studies on the energy dispersive spectroscopy confirm the presence of Cr in Cr substituted CoFe2O4 nanoparticles. Transmission electron microscopy observations revealed that CoFe2O4 and Cr substituted CoFe2O4 nanoparticles are uniformly distributed and not highly agglomerated. Dielectric properties such as dielectric constant (??) and dielectric loss (??) of prepared nanoparticles were investigated as a function of frequency and temperature. The dielectric study reveals that dielectric constant and dielectric loss are higher for Cr substituted CoFe2O4 than the corresponding value of pure CoFe2O4 nanoparticles. Studies on magnetic properties revealed that the saturation magnetization of samples decreases with increasing Cr concentration and lies in the range of 69.67-42.71 emu/g for the prepared samples. Strong red emission and weak blue and UV emissions are observed from the fluorescence spectral analysis of the prepared pure and Cr substituted CoFe2O4 nanoparticles.
Vadivel, M.; Ramesh Babu, R.; Sethuraman, K.; Ramamurthi, K.; Arivanandhan, M.
NASA Astrophysics Data System (ADS)
Effects of nitrogen concentration near the HfOxNy/Si interface on the charge trapping properties of metal-oxide-semiconductor (MOS) capacitors were investigated. The nitrogen concentration in HfOxNy gate dielectric was adjusted by sputtering the Hf target in a nitrogen-flow-modulated ambient. The trapped charges in the HfOxNy dielectric are positive. The mechanism related to the relatively large stress-induced leakage current (SILC) at low electrical fields can be explained using trap-assisted tunneling. On the other hand, the relatively small leakage current found at high electric fields can be attributed to the electron trapping in bulk defects. A small flat-band voltage shift and SILC are observed for devices with a HfOxNy dielectric containing a higher nitrogen at the dielectric/Si interface, which possesses less strain near the interface.
Cheng, Chin-Lung; Chang-Liao, Kuei-Shu; Huang, Ching-Hung; Wang, Tien-Ko
EFFECT OF MgO ON STRUCTURE AND DIELECTRIC PROPERTIES OF CaO-Al2O3-B2O3-SiO2 GLASSES
NASA Astrophysics Data System (ADS)
The effect of MgO on structure and dielectric properties of aluminoborosilicate glasses was investigated. FTIR data indicated that glass network was mainly built by tetrahedral [SiO4], [BO4], [AlO4] and trigonal [BO3]. A small amount of AlO5 or AlO6 units also existed. The glass system was characterized with lower dielectric constant (4.17 4.6) and dielectric loss (12.3 ū 10-4 14.77 ū 10-4) at 1 MHz. With the increase of MgO content, the quantity of AlO5 or AlO6 units decreased. The variation of density showed a decreasing tendency. The dielectric constant and loss were all found to decrease.
Du, Zhao; Zhang, Xuehong; Yue, Yunlong; Wu, Haitao
NASA Astrophysics Data System (ADS)
ZnO nanoparticles (ZnO-NPs) were synthesized by a new, simple sol-gel method in gelatin media (particle size of ZnO ? 30 to 60 nm). Polyurethane/ZnO nanocomposites thin films (PU/ZnO-NPs) were prepared by mixing the ZnO-NPs into PU prepolymer. The nanocomposites were structurally characterized using Fourier transmission infrared (FTIR) spectroscopy. The interaction between ZnO-NPs and PU matrix is studied by analyzing the differences in C=O region and N-H region of FTIR spectra. The morphology of ZnO and PU/ZnO nanocomposites were assessed using transmission electron micrograph, TEM, and field emission scanning electron microscope, FESEM, respectively. The dielectric properties of ZnO-NPs were attributed to the interfacial and orientation polarization. Measurement is reported for the real and imaginary parts of the ac conductivity of ZnO-NPs in the frequency range of 10 to 106 Hz in the temperature range 298-478 K. The experimental results are interpreted in terms of the classical correlated-barrier hopping theory. In addition, the dielectric properties of PU/ZnO nanocomposites (0-15 vol. % filler concentration) were analyzed with respect to frequency. Quantitative analysis based on mixing laws for two-phase spherical dispersion system such as Lichtenecker, Maxwell, Jayasundere and Smith, and Yamada equations was used to predict the effective permittivity accurately up to 15 vol. % of ZnO in PU matrix.
Velayutham, T. S.; Abd Majid, W. H.; Gan, W. C.; Khorsand Zak, A.; Gan, S. N.
The dielectric properties of the hydrogen disordered hexagonal phase (Ih) of water ice have been computed using density functional theory (DFT) based Monte Carlo simulations in the isobaric-isothermal ensemble. Temperature dependent data yield a fit for the Curie-Weiss law of the system and hence a prediction of the temperature of the phase transition from the Ih phase to the hydrogen ordered ice XI phase. Direct simulations around the phase transition temperature confirm and refine the predicted phase transition temperatures and provide data for further properties, such as the linear thermal expansion coefficient. Results have been obtained with both hybrid and semilocal density functionals, which yields insight in the performance of the electronic structure method. In particular, the hybrid functional yields significantly more realistic dielectric constants than the semilocal variant, namely ? ? 116 as opposed to ? ? 151 at 273 K (?experiment = 95). This can be attributed to the tendency of semilocal functionals to be biased to configurations with a large dipole moment, and their overestimation of the dipole moments of these configurations. This is also reflected in the estimates of the Ih/XI transition temperature, which is 70-80 and 90-100 K for the hybrid and semilocal functional respectively. DFT based sampling of the millions of configurations necessary for this work has been enabled by a Tree Monte Carlo algorithm, designed for massively parallel computers. PMID:24392971
Sch÷nherr, Mandes; Slater, Ben; Hutter, J³rg; VandeVondele, Joost
Dielectric properties of MgO-doped compositionally graded multilayer barium strontium titanate films
NASA Astrophysics Data System (ADS)
We have grown 5mol% MgO-doped multilayered Ba1-xSrxTiO3 (BST) films having a nominal thickness of 220nm with compositions of each layer as BST60/40, BST75/25, and BST90/10 (upgraded). We also fabricated undoped upgraded BST and uniform BST60/40 films for comparison. Results show that Mg-doping improves dielectric loss (tan?=0.008) and yields better surface roughness (ś3.1nm) compared to undoped upgraded BST. Mg-doped films displayed excellent temperature stability with temperature coefficient of capacitances of -0.94 and 1.14ppt/░C from 20to90░C and 20to-10░C, respectively. Mg doping resulted in a moderate dielectric tunability (29%) compared to undoped BST (65.5%) at 444kV/cm.
Cole, M. W.; Ngo, E.; Hirsch, S.; Okatan, M. B.; Alpay, S. P.
NASA Astrophysics Data System (ADS)
Rare-earth scandates (ReScO3, with Re =Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, i.e., the entire series for which the individual oxides are chemically stable in contact with Si) were deposited in a temperature-gradient pulsed laser deposition system onto LaAlO3 substrates. The crystallization temperature depends monotonically on the Re atomic number and the Goldschmidt tolerance factor, with crystallization temperatures as low as 650░C for LaScO3 and PrScO3. The dielectric constants of the crystalline films K ?30 (determined by microwave microscopy) are significantly larger than those of their amorphous counterparts. In combination with the large observed band gaps (Eg>5.5eV, determined by ellipsometry), these results indicate the potential of these materials as high-K dielectrics for field-effect transistor applications.
Christen, H. M.; Jellison, G. E.; Ohkubo, I.; Huang, S.; Reeves, M. E.; Cicerrella, E.; Freeouf, J. L.; Jia, Y.; Schlom, D. G.
[Experimental research and analysis on dielectric properties of blood in anemia mice].
The conductivity and permittivity of blood in mice were measured by the AC electrical impedance method at frequency range of 0.1-100MHz, and then the changes of the Cole-Cole parameters of dielectric spectra of blood from phenylhydrazine-induced anemia mice were observed by numerical calculation and curve fitting residual analysis of the Cole-Cole equation. The results showed that hematocrit (Hct) of the mice with phenylhydrazine injection was significantly reduced; the permittivity(epsilon) spectroscopy of blood moved to the low insulating region and its permittivity decreased; conductivity (kappa) spectrum curve of blood moved to the high conductivity zone and conductivity increased; the 2nd characteristic frequency was lower than that in the normal group. There was phenylhydrazine dose dependent in the changes of the Cole-Cole parameters of dielectric spectra of blood. PMID:24645593
Shen, Ben; Liang, Quiyan; Gao, Weiqi; You, Chu; Hong, Mengqi; Ma, Qing
Ti-doped ThO2: a first-principles study of dielectric properties
NASA Astrophysics Data System (ADS)
We determine electronic structure and dielectric response of 25 and 50% Ti-substituted thoria (ThO2), using first-principles density functional theory calculations based on pseudopotentials and a plane wave basis. We find that Th0.75Ti0.25O2 is more promising as a high-k material than Th0.5Ti0.5O2. We show that the IR-active phonon modes in pure thoria can be tuned upon Ti doping and the softened modes cause an enhanced dielectric response of 25% Ti-doped thoria. As the material remains insulating, it holds promise for applications such as a gate oxide material.
Dutta, Gargi; Waghmare, Umesh V.
Dielectric and ac conduction properties of zinc phthalocyanine (ZnPc) thin films
NASA Astrophysics Data System (ADS)
The dielectric responses of zinc phthalocyanine (ZnPc) thin films, deposited using the vacuum evaporation technique, were studied as functions of frequency and temperature. The conductivity of the deposited films decreases with increase in temperature. The dielectric studies clearly indicated that the Debye type of polarization exists in these films. The relaxation phenomena have been confirmed from the Cole-Cole plot. The relaxation times have been evaluated from the plot and were found to be (?a) 0.0137 and 0.0106s at 303 and 403K, respectively. The prevailing conduction mechanism in ZnPc films, under an ac field, was found to be electronic hopping. The activation energy was evaluated from the Arrhenius plot and was found to be 1.28eV. Based on the structure, and with the help of quantum mechanics calculations, the electronic structure and behavior that upheld our experimental results were identified.
Senthilarasu, S.; Sathyamoorthy, R.; Ascencio, J. A.; Lee, Soo-Hyoung; Hahn, Y. B.
Structural and dielectric properties of Nd/Ca co-doped bi-ferrite multiferroics
NASA Astrophysics Data System (ADS)
Single-phase polycrystalline samples of Bi0.8Nd0.2-xCaxFeO3 (x = 0.0, 0.1) were synthesized by chemical coprecipitation method. X-ray diffraction patterns accompanied by Rietveld-refined crystal structure parameters reveal the phase transition of Bi0.8Nd0.1Ca0.1FeO3 with rhombohedral R3c symmetry to triclinic structure of Bi0.8Nd0.2FeO3 sample. Frequency dependence of dielectric constant (?') and dielectric loss (tan?), infers enhancement of both ?' (tan?) in narrow band gap of Nd/Ca co-doped BFO as compare to wide band pristine BFO.
Kumar, Ashwini; Sharma, Poorva; Varshney, Dinesh
Dielectric properties of Ba(Ti1-yYy)O3 ceramics
Temperature and frequency dependence of the real (?') and imaginary (?'') parts of the dielectric permittivity of Ba(Ti1-yYy)O3 (0.028<=y<=0.258) ceramic samples were studied in the temperature range 12-500 K at 102, 103, and 104, and 105 Hz. The permittivity peaks are rounded and frequency dispersive when y>0.028. The maximum of the rounded peak (?m') decreases with an increase in the
Zhi Jing; Chen Ang; Zhi Yu; P. M. Vilarinho; J. L. Baptista
Dielectric response and electric properties of organic semiconducting phthalocyanine thin films
NASA Astrophysics Data System (ADS)
The dielectric function of some phthalocyanine compounds (ZnPc, H2Pc, CuPc, and FePc) were investigated by analyzing the measured capacitance and loss tangent data. The real part of the dielectric constant, ?1, varies strongly with frequency and temperature. The frequency dependence was expressed as: ?1 = A?n, where the index, n, assumes negative values (n < 0). In addition, the imaginary part of the dielectric constant, ?2, is also frequency and temperature dependent. Data analysis confirmed that ?2 = B?m with values of m less than zero. At low frequencies and all temperatures, a strong dependence is observed, while at higher frequencies, a moderate dependence is obvious especially for the Au-electrode sample. Qualitatively, the type of electrode material had little effect on the behavior of the dielectric constant but did affect its value. Analysis of the AC conductivity dependence on frequency at different temperatures indicated that the correlated barrier hopping (CBH) model is the most suitable mechanism for the AC conduction behavior. Maximum barrier height, W, has been estimated for ZnPc with different electrode materials (Au and Al), and had values between 0.10 and 0.9 eV For both electrode types, the maximum barrier height has strong frequency dependence at high frequency and low temperatures. The relaxation time, ?, for ZnPc and FePc films increases with decreasing frequency. The activation energy was derived from the slopes of ? versus 1/T curves. At low temperatures, an activation energy value of about 0.01 eV and 0.04 eV was estimated for ZnPc and FePc, respectively. The low values of activation energy suggest that the hopping of charge carriers between localized states is the dominant mechanism.
Saleh, A. M.; Hraibat, S. M.; M-L. Kitaneh, R.; Abu-Samreh, M. M.; Musameh, S. M.
Broadband dielectric spectroscopy in the frequency range from 10 to 10Hz was employed to study the molecular dynamics of various triphenylene and benzene derivatives in their isotropic and liquid crystalline phases. For all derivatives, two relaxation processes were detected in their columnar mesophases. The ?-process shows an Arrhenius-like temperature dependence with activation energies between 37 and 40 kJ mol. This
Herbert Groothues; Friedrich Kremer; David M. Collard; C. P. Lillya
X-Ray Radiation Effects on the Dielectric Properties of PZT Ceramics
We have systematically studied the X-ray radiation effects on PZT thin ceramic disk provided by CTS Communications Components, Inc using the X-ray beam line in the Center for Advanced Micro-Structure and Devices (CAMD) in Baton Rouge, Louisiana. The photo energies of the X-ray range from 2000 eV to 8000 eV. The beam size is 10.0cmū1.0cm.We measure the dielectric constant in
J. T. Wang; C. Zhang; A. Fitzgerald; Y. Fu; S. Hall
One of the interesting aspect of the cooperative Jahn-Teller effect is the constructing in its framework the microscopic theory of ferro- and antiferroelectricity. The main peculiarity of the Jahn-Teller ferro- and antiferro-electrics seems to be the simultaneity of the dielectric and elastic anomalies. This peculiarity is determined by the fact that the vibronic nature of the ordering dipole moments dictates
M. D. Kaplan; B. G. Vekhter
Eighty years after its experimental discovery, a microscopic description of induced nuclear fission based solely on the interactions between neutrons and protons and quantum many-body methods still poses formidable challenges. The goal of this paper is to contribute to the development of a predictive microscopic framework for the accurate calculation of static properties of fission fragments for hot fission and thermal or slow neutrons. To this end, we focus on the 239Pu(n,f) reaction and employ nuclear density functional theory with Skyrme energy densities. Potential energy surfaces are computed at the Hartree-Fock-Bogoliubov approximation with up to five collective variables. We find that the triaxial degree of freedom plays an important role, both near the fission barrier and at scission. The impact of the parameterization of the Skyrme energy density on deformation properties from the ground-state up to scission is also quantified. We introduce a general template for the detailed description of fission fr...
Schunck, N; Carr, H; Knoll, A
Influence of Radiation on the Dielectric Properties of XLPE Based Insulation Systems
NASA Astrophysics Data System (ADS)
The paper discusses the possibilities of acquiring and processing the dielectric data in the range of very low frequency (VLF) and also design and construction of an impedance analyzer for measurements in this frequency range. The impedance measurements in the VLF range were used for investigation of the influence of radiation on the cross-linked polyethylene cable dielectric. An expressive ?-type relaxation process was found in this type of cable. Most of the dielectric response parameters of the process depend significantly on the absorbed dose of radiation. The analysis of the process parameters showed that the most probable reason of the structural changes in cross-linked polyethylene was additional cross-linking. The results also proved that the impedance measurements in the VLF range could be effectively used in practice for estimation of the absorbed dose in the cross-linked polyethylene cables stressed by radiation.t data only. In order to identify or classify motion, data processing in real time is needed.
?urman, VladimĒr; Lelßk, Jaroslav
DSC, TGA and dielectric properties of carboxymethyl cellulose/polyvinyl alcohol blends
NASA Astrophysics Data System (ADS)
Films with different compositions of polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC) blends have been prepared using the casting method. Differential scanning calorimetery (DSC), thermogravimetric analysis (TGA) and dielectric spectroscopy of all compositions have been investigated. It was found that PVA and CMC are compatible in the studied range of composition. With increasing CMC content, the thermal stability of PVA increases. Based on DSC and TGA data, the activation energies of all the investigated samples were calculated. The absorption edge ( Ea) was also determined from Ultraviolet-visible (UV-vis) spectra. Dielectric permittivity, loss tangent and ac conductivity of all samples were studied as functions of temperature and frequency. The results show that the dielectric dispersion consists of both dipolar and interfacial polarization. The frequency dependence of the ac conductivity indicates that the correlated barrier hopping (CBH) is the most suitable mechanism for conduction. The polaron binding energy ( UM) was determined. Results of the present system are compared with those of similar materials.
El-Sayed, S.; Mahmoud, K. H.; Fatah, A. A.; Hassen, A.
NASA Astrophysics Data System (ADS)
Large single crystal of triglycine sulphate (dimension 100 mm along monoclinic b-axis and 15 mm in diameter) was grown using the unidirectional solution growth technique. The X-ray diffraction studies confirmed the growth/long axis to be b-axis (polar axis). The dielectric studies were carried out at various temperatures to establish the phase transition temperature. The frequency response of the dielectric constant, dielectric loss and impedance of the crystal along the growth axis, was monitored. These are typically characterized by strong resonance peaks in the kHz region. The piezoelectric coefficients like stiffness constant ( C), elastic coefficient ( S), electromechanical coupling coefficient ( k) and d 31 were calculated using the resonance-antiresonance method. Polarization ( P)-Electric field ( E) hysteresis loops were recorded at various temperatures to find the temperature-dependent spontaneous polarization of the grown crystal. The pyroelectric coefficients were determined from the pyroelectric current measurement by the Byer and Roundy method. The ferroelectric domain patterns were recorded on (010) plane using scanning electron microscopy and optical microscopy.
Justin Raj, C.; Kundu, Swarup; Varma, K. B. R.
NASA Astrophysics Data System (ADS)
(Pb1-1.5xLax)(Zr0.66Sn0.23Ti0.11)O3 (PLZST) ceramics with different lanthanum (La3+) content (x = 0¢6%) were prepared by conventional solid state reaction process, and exhibited excellent electrical properties with high switching field from AFE to FE phase and electric breakdown strength. The maximum dielectric constant (?m) and its corresponding temperature (Tm) decreased with La3+ doping and a phase transition from rhombohedral ferroelectric (FE) to tetragonal antiferroelectric (AFE) state was found at 2% La3+ doping. At room temperature, a maximum energy density of 1.47 J cm?3 was obtained for x = 4%. In addition, electric-field-dependent energy storage properties of PLZST (x = 4%) ceramics have been investigated, which could be ascribed to the AFE¢FE phase transition associated with the increase of strain.
Zhuo, Fangping; Li, Qiang; Li, Yuanyuan; Gao, Jinghan; Yan, Qingfeng; Zhang, Yiling; Chu, Xiangcheng; Cao, Wenwu
In this work, temperature stable microwave dielectric materials (1 - x)AMoO(4)-xTiO(2) (A = Ca, Sr) were prepared by a solid state reaction method. The phase composition, sintering behaviors, microstructures, microwave dielectric properties, effective permittivity and vibrational phonon modes were investigated. The X-ray diffraction pattern and scanning electron microscope analysis indicated that the AMoO(4) (A = Ca, Sr) phase could coexist with the TiO(2) phase. The effective dielectric constants of the AMoO(4)-TiO(2) composites were calculated by the finite element method (FEM), compared with the measured values and the numerical results obtained by the classical mixing rules. The correlation between the dielectric properties and the crystal structures were studied using IR and Raman spectroscopy. The infrared spectra were analyzed using the classical harmonic oscillator model, and revealed that the external vibration modes of AMoO(4) (A = Ca, Sr) had the most significant influence on the dielectric constant. The Raman spectra showed that there were strong interactions in the [MoO(4)] tetrahedron due to the sharp and intense Raman modes. Finally, the low-firing (900 ░C) microwave dielectric ceramics were obtained with 3 wt% H(3)BO(3)-CuO addition (BCu), and they possess good microwave dielectric properties with ?(r) = 10.6-13, high Qūf values (40?700-72?050 GHz), and near-zero temperature coefficients of resonant frequency (TCF or ?(f) values). These results also show that (1 - x)AMoO(4)-xTiO(2)-BCu (A = Ca, Sr) ceramics are good candidates for microwave electronic device applications. PMID:23124534
Guo, Jing; Zhou, Di; Wang, Lu; Wang, Hong; Shao, Tao; Qi, Ze M; Yao, Xi
NASA Astrophysics Data System (ADS)
Barium titanate (BTO) with different morphology is prepared through hydrothermal method using titania spheres as precursor, then calcined at different temperatures and ultimately coated with cobalt ferrite (BTO/CFO). The dielectric dispersion of the composite containing BTO (75 wt. % ratio in paraffin wax) shows evidence of resonance behaviour in the microwave spectrum, rather than the usually observed relaxation mode. The imaginary part of permittivity (??) displays a strong peak in the 10-13 GHz frequency region, especially for buckhorn-like BTO (hydrothermally synthesized at 110 ░C and calcined at 1100 ░C). The dielectric response anomaly of BTO in special morphology is due to the emission of plane acoustic waves caused by electrostrictive and converse piezoelectric effects. An accepted model is adopted to simulate the resonance frequency. The minimum reflection loss of cauliflower-like BTO (hydrothermally synthesized at 110 ░C, then calcined at 600 ░C for 2 h, 75 wt. % ratio) in paraffin wax reaches -30.831 dB at 10.56 GHz with a matching thickness of 2 mm, lower than all the reported values. When the sintering temperature is changed to 1100 ░C (buckhorn-like BTO), the minimum reflection loss value is -24.37 dB at 12.56 GHz under the thickness of 3 mm. After combination with CFO, the value reaches -42.677 dB when the thickness is 5.6 mm. The ginger-like BTO (hydrothermally synthesized at 200 ░C and calcined at different temperatures) is inferior in microwave reflection reduction. The electromagnetic interference shielding effectiveness of buckhorn-like BTO composite is calculated to be -12.7 dB (94.6% shielding) at resonance frequency (2 mm, 11.52 GHz). This work clearly shows the potential to tune the dielectric property of ferroelectrics through control of morphology, facilitating new comprehension of the ferroelectrics in microwave regime.
Ji, Renlong; Cao, Chuanbao
Dielectric Properties and Defect Chemistry of WO3-Doped K0.5Na0.5NbO3 Ceramics
NASA Astrophysics Data System (ADS)
The dielectric properties and conductivity behavior of WO3-doped K0.5Na0.5 NbO3 ceramics were investigated as a function of temperature (25░C to 600░C) and frequency (40 Hz to 106 Hz). The dielectric loss and direct-current (DC) conductivity of the ceramics depend strongly on the tungsten content. A high-temperature dielectric relaxation near temperature of 500░C was observed and analyzed using the semiempirical complex Cole-Cole equation. The activation energy of the dielectric relaxation was estimated to be ś2 eV and increased with increasing WO3. The frequency-dependent conductivity can be well described by the universal dielectric response law. The activation energy obtained from the DC conductivity changes from 0.93 eV to 1.49 eV. A possible mechanism for the high-temperature dielectric relaxation and conductivity is proposed based on the activation energy value and defect compensation.
Wu, Shuangshuang; Zhu, Wenfeng; Liu, Laijun; Shi, Danping; Zheng, Shaoying; Huang, Yanming; Fang, Liang
NASA Astrophysics Data System (ADS)
A 'misplaced-displacive' Ca 1.5NbTi 1.5O 7 (CNT) Fd3»m, cubic pyrochlore phase ( a=10.2171 ┼) has been successfully synthesised via a metallorganic decomposition route, enabling a much lower final annealing temperature than the conventional solid state reaction route. This