Effect of microstructure on electrical properties of Li and Cr substituted nickel oxide

Abstract

LCNO (Li_0.35Cr_0.10Ni_0.55O) sample was prepared by modified sol–gel method and annealed at different temperatures (400, 800 and 1000 °C) in order to have variation in the size of grains and grain boundaries. The crystallinity and phase purity have been studied by employing the X-ray diffraction (XRD) technique. All the samples are crystallize to cubic symmetry with $Fm\overline 3 m$ space group and, XRD patterns could be analysed by employing the Rietveld method. The microstructural and elemental analysis of the sample has been carried out by using the field emission scanning electron microscopy (FESEM). The grain size increases with the increase in annealing temperature which leads to increase the dielectric constant with the grain size. Interestingly, the enhancement of dielectric constant with the increase in grain size could be explained by the Barrier Layer Capacitances (BLCs) model. The frequency dispersion of dielectric constant could be explained by the Maxwell Wagner relaxation model. Furthermore, it is also observed that the activation energy obtained from dielectric relaxation analysis is comparable with the activation energy obtained by impedance analysis (Cole–Cole). In addition, the correlation between microstructure (grains and grain boundaries) with electrical transport properties of LCNO has been reported.