Mössbauer spectra of vanadates

1. Synthesis and Properties of Magnetic Ceramic Nanoparticles Monica Sorescu, Duquesne University, DMR 0854794 Outcome Researchers at Duquesne University showed that magnetic ceramic nanoparticles can be produced through mechanochemical activation by high energy ball milling of transition metal oxides and α-Fe2O3. Impact/ benefitsThe magnetic ceramic nanoparticles showed various structural, magnetic and thermal properties of interest in catalysis, gas sensing and energy-related applications. Explanation Mechanochemical activation homogeneously mixed the starting materials of α-Fe2O3 and V2O5 and substantially decreased their average grain sizes. The Mössbauer spectroscopy studies showed that the spectrum of the mechanochemically activated composites consisted of three sextets and one doublet, indicating the occurrence of V5+-Fe3+ ion substitutions in the corresponding α-Fe2O3 and V2O5 lattices, respectively. The partially V5+-substituted α-Fe2O3 phase and Fe3+-substituted V2O5 could be the important intermediate phases in the production of FeVO4 single phase. Mössbauer spectra of vanadates

2. Synthesis and Characterization of Vanadium Oxide Doped Hematite xV2O3∙(1-x)-Fe2O3 Solid Solution Monica Sorescu, Duquesne University, DMR 0854794 xV2O3.(1-x)Fe2O3(x = 0.1, 0.3, 0.5 and 0.7) solid solutionswere successfully synthesized by mechanochemical activation of V2O3 and α-Fe2O3 mixtures. X-ray powder diffraction (XRD), Mössbauer spectroscopy, scanning electron microscopy (SEM), simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC-TGA), and optical diffuse reflectance spectroscopy were combined for detailed studies of phase evolution of xV2O3.(1-x)Fe2O3 solid solution under the mechanochemical activation process. The Mössbauer studies indicated that the spectrum of the mechanochemically activated composites consisted of sextets and a doublet upon duration of milling process, indicating the occurrence of V3+-Fe3+ ion substitutions in the corresponding α-Fe2O3 and V2O3 lattices, respectively. Complete solid solution exists after 12 h ball-milling time for all studied x values. Prof. Monica Sorescu next to a Mössbauer spectrometer used to measure the magnetic properties of synthesized nanoparticles at atomic resolution scale Monica Sorescu and Tianhong Xu, Particle size effects on the thermal properties of hematite, Journal of Thermal Analysis and Calorimetry 107, 463-469 (2012)

3. Studies on Structural, Magnetic and Thermal Properties of xFe2TiO4-(1-x)Fe3O4 (0 ≤ x ≤ 1) Pseudo-binary System Monica Sorescu, Duquesne University, DMR 0854794 The xFe2TiO4-(1-x)Fe3O4pseudo-binary systems(0 ≤ x ≤ 1) of ulvöspinel component were synthesized by solid-state reaction between ulvöspinel Fe2TiO4 precursors and commercial Fe3O4 powders in stochiometric proportions. The fraction of Fe2+ in both tetrahedral and octahedral sites increases with the increase in Ti4+ content, due to the substitution and reduction of Fe3+ by Ti4+ that maintains the charge balance in the spinel structure. For x in the range of 0 ≤ x ≤ 0.4, the solid solution is ferrimagnetic at room temperature. However, it shows weak ferrimagnetic and paramagnetic behavior for x in the range of 0.4 < x ≤ 0.7. When x > 0.70, it only shows paramagnetic behavior, with the appearance of quadrupole doublets in the Mössbauer spectra. Simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC-TGA) studies showed that magnetite is not stable, and thermal decomposition of magnetite occurs with weight losses accompanying with exothermic processes under heat treatment in inert atmosphere. Mössbauer spectra of titanomagnetites Monica Sorescu et al, Journal of Magnetism and Magnetic Materials 324, 1453-1462 (2012)