Temperature dependent impedance spectroscopy and electrical transport mechanism in sol-gel derived MgCr2O4 spinel oxide

Magnesium chromite (MgCr2O4) spinel oxide was synthesized by sol-gel auto-combustion technique. Room temperature X-ray powder diffraction pattern was refined by Fullprof which confirmed the formation of single-phase cubic structure with Fd3m space group. The complex impedance spectroscopy was employed to investigate the charge transport mechanism within the temperature range of 423-573K and the impedance data were finely fitted for temperature dependent Nyquist plot to track down the equivalent circuit model [(RGCG)(R(Gb)Q(Gb))]. The temperature and frequency dependent AC conductivity was found to follow Jonscher double power law and the slope of conductivity indicated the correlated barrier hopping (CBH) as a dominant conduction model in the material. The grain and grain boundary polarization was analyzed by electric modulus which confirmed the two phase response of the material. The dielectric relaxation exhibited dispersion in the low frequency region which owed to the interfacial effects.