No abstract

The conductivity and Seebeck coefficient of the perovskite‐type oxides La1−xSrxCoO3−δ false(x=0–0.7false) were measured in 10–5−1 normalatm O2 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 La1−xSrxCoO3−δ with α<60.3°–60.4° ( LaCoO3−δ above 800°C and La1−xSrxCoO3−δ with x>0.5 at room temperature), the conductivity decreases with temperature, suggesting metallic conduction. For La1−xSrxCoO3−δ with α>60.4° , 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.