Electronic structure and electrical transport properties of LaCo1-xNixO3 (0 ≤ x ≤ 0.5)

Abstract

The structural analysis of LaCo1−xNixO3 (0 ≤ x ≤ 0.5) samples assures single phase rhombohedral structure with space-group Rc. Electronic structure of these samples has been studied by x-ray absorption near edge spectroscopy (XANES) at K-edge of O, Ni, Co and M5,4 edge of La. These studies confirm the trivalent state of Co/Ni and La in all the compositions. Upon substitution of the Ni at the Co site in LaCoO3, the O K-edge spectra show a feature about 1.2 eV lower than that of LaCoO3. This feature keeps on growing as the concentration of the Ni is increasing. This is consistent with our resistivity data which shows drastic decrease in resistivity with the Ni substitution. The resistivity data have been analyzed using Arrhenius and Efros-Shklovski's type variable range hopping models in different temperature ranges. The activation energy decreases and localization length increases systematically with increase in the Ni concentration. Observed features have been explained on the basis of change in charge-carrier density with substitution. The disorder-induced localization of carriers is found to govern conduction mechanism and resistivity behavior in substituted sample.