Electric transport properties study of spinel ZnCr2O4

Abstract

We have carried out the electric transport property study of spinel ZnCr2O4 insulating oxide by the help of complex impedance and modulus technique. The sample was synthesized by conventional method and crystallinity of phase was analyzed by xrd pattern. Surface morphology and porosity was observed from the scanning electron microscope image. Direct band gap (Eg=3.4eV) and indirect band gap (Eg=1.49eV) was found from UV spectroscopic analysis. Co contribution of grain and grain boundary effect is found at room temperature and continued some point below 200oC. Electrode surface polarization was found responsible for conduction mechanism in the sample at high temperature at and above 200oC. Grain effect is supposed to be dominant below the room temperature (RT). The conductivity behavior is found to obey Jonscher’s universal power law. Frequency exponent study revealed three different conduction mechanism, (a) quantum mechanical tunneling, 200oC ˂ T ˂ 260oC, (b) small polaron conduction mechanism at 260oC ˂ T ˂ 355oC and (c) Correlated barrier hopping at 355oC ˂ T ˂ 400oC. The activation energies were found to be 0.74eV, 1.40eV and 1.07eV for the above stated temperature range respectively for corresponding conduction process