Study of sintering behaviour and electrical conductivity of Cr-Zn-Fe-O system

A series of chemical compositions based on Cr, Fe and O with Zn as a partia lly substituting ion has been prepared in the general formula ZnxCr1-xFe2O by coprecipitation method using NH4OH as the precipitating agent at pH=10.3 . The prepared samples were identified by both thermal analysis (DTA and TG A) and X-ray diffraction (XRD). it was found that no single phase was obtai ned for any of the studied compositions but a mixture of different phases w as observed, depending on the molar percentage of zinc ion substitution as well as on the sintering temperature. The temperature dependence of the ele ctrical conductivity, sigma, of the prepared samples was plotted between 25 and 680 degrees C. It was observed that the electrical conductivity increa sed with temperature for both samples with x=0.00 and 0.80 Zn ion content w hile it was nearly temperature independent for samples with intermediate Zn concentration x=0.2 and 0.5 mol fraction. The activation energy, E-a, calc ulated from the linear relation, lg sigma-1000/T for the final mixtures (si ntered at 1300 degrees C) was calculated.