Oxygen Nonstoichiometry and Thermo-Chemical Stability of Perovskite-Type La_0.6Sr_0.4Co_1-yFe_yO_3-δ(y= 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) Materials

The oxygen nonstoichiometry of La 0.6 Sr 0.4 Co 1- y Fe y O 3- δ (LSCF) mixed-conducting perovskite oxides strongly depends on the iron content: the cobalt-rich compounds ( y = 0, 0.2, 0.4) were previously reported to show a sharp decrease in oxygen content with reducing atmosphere, while the oxygen vacancy concentration increased steadily for the iron-rich compounds ( y = 0.6, 0.8) with a plateau at intermediate oxygen partial pressures for y = 1. Here we measured the oxygen content of LSCF with y = 0.5 by thermogravimetry and coulometric titration as a function of oxygen partial pressure and temperature. No transitional behavior could be observed for La 0.6 Sr 0.4 Co 0.5 Fe 0.5 O 3- δ , the oxygen nonstoichiometry showed the same trend as for the cobalt-rich compounds. While the cobalt-rich compounds exhibit a metallic band structure, a semiconducting model fits the data best for the iron-rich compounds. Except for y = 1, the thermo-chemical stability of LSCF was little affected by the iron dopant content, all compounds (0 ≤ y ≤ 0.8) decomposed at similar oxygen partial pressures.