Relative content of the Cr4+ ion and electrical conductivity of La0.75Ca0.25Cr0.75Fe0.25O3

La0.75Ca0.25Cr0.75Fe0.25O3 is synthesized by a wet chemical method and the electric conductivity of the compound in air is measured over a temperature range from 296 to 1083 K. Arrhenius plot for La0.75Ca0.25Cr0.75Fe0.25O3 is composed of two line segments and the discontinuity is at 532 K. The approximate calculation for the temperature dependence of the electrical conductivity of the compound has been performed in consideration of the thermodynamic equilibrium between the Cr3+ and Cr4+ ions in the compound. The electrical conductivity of lanthanum chromite is directly proportional to the relative content of the Cr4+ ion in the compound and the relative content of the Cr4+ ion in La0.75Ca0.25Cr0.75Fe0.25O3 increases with temperature. The activation energy and the electron hopping frequency may have more significant effect on the electric conductivity of the compound. The occurrence of the oxygen deficiency in the doping lanthanum chromite can be explained by the calculated results.