Abstract

The oxygen nonstoichiometry of La_0.6Sr_0.4Co_1-yFe_yO_3-δ (y = 0.2, 0.4, 0.6, 0.8) was measured by high temperature gravimetry and coulometric titration. The results of the oxygen nonstoichiometry measurements could be categorized into Co rich compounds (y = 0.2, 0.4) and Fe rich compounds (y = 0.6, 0.8). The Co rich compounds decomposed into A₂BO₄ and CoO at relatively high P_O2, i.e. ca.10⁻⁹ bar at 873 K, and ca. 10⁻⁶ bar at 1073 K. The apparent decomposition P_O2 in the case of the Fe rich compounds shifted to the lower P_O2 side, i.e. ca.10⁻²¹ bar at 873 K, and ca. 10⁻¹⁵ bar at 1073 K. Before reaching this P_O2, the gradual decomposition of the Fe rich compounds was observed by atmosphere controlled high temperature XRD. From the results of the measurement procedure dependence of the coulometric titration data, the actual decomposition P_O2 of the Fe rich compounds can be considered almost comparable to those of the Co rich compounds.