Temperature dependence of electrical and thermal properties for perovskite-type rare earth cobalt oxide solid solutions Pr1−xTbxCoO3 and their metal–insulator transition behavior

We prepared perovskite-type rare earth cobalt oxide solid solutions Pr1−xTbxCoO3 (x = 0, 0.25, 0.5, 0.75, and 1) and investigated their metal–insulator transition behavior from the temperature dependence of electrical conductivity and specific heat. The solid solution exhibited cubic perovskite for x = 0 and 0.25 while orthorhombic phase was observed above 0.5, resulted in the distortion of CoO6 octahedron. The metal–insulator transition temperature of Pr1−xTbxCoO3 determined from both the electrical conductivity and specific heat measurements increased systematically with increasing x values. It is thus considered that the average ionic size of the R-site rare earth elements had an important role on the metal–insulator transition behavior and hence on the electrical properties. These results suggested that the metal–insulator transition temperature could be controlled by the chemical composition of the solid solutions of two type rare earth elements containing cobalt oxides.