EPR, μ -Raman and Crystallographic properties of spinel type ZnCr 2O4

Abstract

Structural, vibrational and electron paramagnetic resonance (EPR) analysis for compound ZnCr2O4 are shown in this work. These types of materials are used in technological applications as humidity sensors and piezoelectric devices. The compound was obtained by mean of solid state reaction technique from binary precursors ZnO and Cr2O3. After three thermal treatments the sample structure was monitoring using X ray diffraction (XRD), the spinel cubic phase has been indexed within O 7h(Fd3m) spatial group. It is observed normal spinel phase. Micro-Raman analysis revealed bands for normal vibration modes of Zn and Cr atoms in tetrahedral and octahedral environments formed by oxygen atoms at approximately 400 and 900 cm-1, respectively. Bands around 941 cm-1 are associated possibly to vacancies in the tetrahedral and octahedral sites due to interaction between Zn and Cr ions. EPR signal from 150 to 300 K isothermals indicates a transition between inverse spinel to normal spinel type in a central field around 3350 G. A signal at approximately 3400 G corresponding to the C'r+3 in tetrahedral sites is observed near the central field. © 2009 IOP Publishing Ltd.