Figure ) shows the X-ray diffractograms of the nickel ferrite samples. PDF4+-file 04-014-8286 is used to perform a Rietfeld refinement, by the means of which crystallite sizes of 3.3 nm and 31 nm are calculated ((220) reflection). BET surface area analysis showed 102 m 2 •g -1 and 13 m 2 •g -1 for the lower and higher crystallite size samples, respectively. Figures and) show the ATR-FIR and -MIR spectra of the samples, respectively. The comparison of the MIR region with the literature and spectra of glycine and the nitrate precursors as well as the ratio of intensities of these bands allow the assignment of the bands at 1036 cm -1 , 1338 cm -1 , 1393 cm -1 and 1634 cm -1 mainly to nitrate residues and water. The signal at around 2345 cm -1 is assigned to CO2. Comparing the small and large crystallite size samples spectra, it is obvious, that the small crystallite sample contains more residual nitrate due to the deficiency in glycine, which is promoting the synthesis as a fuel compound. The signals in the FIR region are assigned to vibrations of bonds between oxygen and metal ions located in tetrahedral and octahedral sites. More specifically, Waldron et al. reported four optically active bands in the FIR range for normal spinels: One higher and one lower wavenumber band representing the vibrations between oxygen and metal ions in tetrahedral and octahedral sites, respectively, and two bands occurring at low wavenumbers representing lattice vibrations. For inverse spinels or spinels with increasing degree of inversion such as NiFe2O4 on the other hand, Josyulu et al. reported the formation of a shoulder on the low wavenumber side of the band, which represents metal ions at octahedral sites. In exchange, a shoulder on the high wavenumber side of the band representing metal ions at tetrahedral sites should be visible. This assignment is well suitable to the FIR spectrum of the larger crystallite sample showing signals at wavenumbers of 189 cm -1 , 235 cm -1 (both lattice vibrations), 364 cm -1 including a low wavenumber shoulder (octahedrally coordinated metal ions) and 557 cm -1 including a high wavenumber shoulder (tetrahedrally coordinated metal ions). In the FIR spectrum of the smaller crystallite sample no signals can be observed in the lattice vibration region and the signals of metal ions at octahedral and tetrahedral sites are extremely broadened. This was predicted to occur by Waldron et al. due to disorder in the lattice, which is explainable by the lower crystallinity of this sample according to the X-ray diffractogram. The FIR band positions reported by Waldron are shifted by approximately 30 cm -1 to 396 cm -1 and 587 cm -1 , respectively, without any shoulders. The samples described there were prepared by precipitation and thermal decomposition of oxalates. Most sources are consistent in showing two main bands in the FIR region, but differ considerably in positions of the bands, which might indicate different degrees of spinel inversion and disorder, possibly depending on the preparation method . eV. Table compares the results of with the samples discussed here. For the larger crystallite size sample, a good agreement is found, whereas a deviation of -0.4 eV, -0.6 eV and -0.6 eV is found for the smaller crystallite size sample for peaks 2, 3 and 4, respectively and resulting in a different ratio of peak areas as well (1:6.9:4.7:3.0 small crystallite size sample, 1:1.5:0.83:0.63). The Fe2p3/2 satellite signal confirms the presence of Fe 3+ as predominant Fe species in both samples. Often, a simpler model consisting of two peaks only is chosen in the literature . The lower binding energy component is assigned to octahedrally coordinated ions and the higher binding energy component is assigned to tetrahedrally coordinated ions in this case. This approach is shown in figure . This is in agreement with the FIR spectrum of the larger crystallite size sample, which exhibits a low wavenumber side shoulder in the band representing the octahedrally coordinated ions. Agreement with peak positions presented in differs considerably for peaks 1 -5 and is worst for peaks 1 and 5 in the larger crystallite size sample. Reducibility is increased in the reaction with both reducing agents in the lower crystallite size sample. The H2-TPR curves consist of two maxima in both samples, but occur at higher temperatures in the larger crystallite size sample (390 °C and 470 °C vs. 520 °C). Furthermore, the lower temperature maximum is much less pronounced in the larger crystallite size sample and difficult to localize exactly. The CO-TPR curves show a temperature shift of the maxima to higher temperatures for the larger crystallite size sample as well and the area under the curve is considerably larger for the smaller crystallite size sample. Figure shows the ex-situ XRD results for the nickel ferrite samples after CO-TPR. Face centered cubic intermetallic phases of the nominal composition Ni0.33Fe0.67 are formed in both samples. The magnified area shows the (002) reflection region of graphite. The formation of graphite appears to be higher in the smaller crystallite size sample, where the share of graphite is 34 % in comparison to 16 % only in the larger crystallite size sample according to quantitative XRD phase analysis. This might be related to the higher surface area leading to an increased consumption of CO during the TPR procedure. Examples of H2-TPR curves in the literature consistently exhibit two distinct maxima occurring at 360 °C and 536 °C and 341 °C and 543 °C for example, which agrees better with the larger crystallite size sample in terms of maxima positions, but not with the smaller crystallite size sample. Pereira Borges et al. and Benrabaa et al. report a crystallite size of 18.11 nm and 6 nm, respectively. The TPR curves obtained here might be interpreted as sign of the metal ions in the smaller crystallite size sample being not as strongly bound as in the higher crystallinity sample, resulting in an increased reducibility.