Electrical Conductivity and Seebeck Coefficient of Nonstoichiometric La_1 − x Sr_x CoO_3 − δ

The conductivity and Seebeck coefficient of the perovskite‐type oxides were measured in gas at temperatures 25°–1000°C. The results are discussed in relation to the lattice‐parameter and oxygen non‐stoichiometry. Close relationships were found between the temperature dependence of the conductivity and the rhombohedral angle, α. For with ( above 800°C and with at room temperature), the conductivity decreases with temperature, suggesting metallic conduction. For with, the conductivity increases with temperature like semiconductors. In the oxides with metallic conduction, the conductivity was found to decrease with increase in the oxygen vacancy concentration. Because the conduction band is composed of the Co‐O‐Co network, it is considered that the band is distributed by the formation of oxygen vacancies and becomes narrower, resulting in the decrease in conductivity.