DC electrical resistivity studies and structure of Ni0.5Zn0.5CrxFe2-xO4 nanoferrites

Chromium substituted Ni-Zn nano ferrite samples with composition Ni0.5Zn0.5CrxFe2-xO4 (x = 0.00 to 0.25 in steps of 0.05) have been prepared by autocombustion method employing citric acid as an oxidant. Structural, morphological and microstructural characterizations were done on the sintered powders at 1000 degrees C while the DC electrical resistivity studies have been performed on the pellets sintered at the same temperature. The thermogravimetric and differential thermal analysis (TG-DTA) studies indicated the presence of broad exotherm and valley centered about temperature of 400 degrees C. The formation of single-spinel phase has been observed for all the samples. The ionic packing coefficient, vacancy parameter and fulfillment coefficient have all been obtained for each composition. The scanning electron micrographs showed the formation of fine grains with size very less than 1 mu m in all samples with a little agglomeration. The observed variation in DC electrical resistivity and activation energy with Cr3+ substitution are attributed to the modifications in microstructure, structural defects and the influence of Cr3+ ions with support of hopping mechanism.