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_0.6Sr_0.4Co _1-yFe_yO_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_0.4Co_0.5Fe _0.5O_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.