Introduction of A-site deficiency into La0.6Sr0.4Co0.2Fe0.8O3–δ and its effect on structure and conductivity

A-site deficiency was introduced intentionally into the mixed conducting perovskite ABO3-type oxide, La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF=6/4/2/8), in order to create additional oxygen vacancies. With increasing Sr-deficiency, z in La0.6Sr0.4–zCo0.2Fe0.8O3–δ, its lattice parameters and oxygen content gradually increased and decreased, respectively, which strongly suggested that additional oxygen vacancies were created in the lattice. It is expected that these additional oxygen vacancies improve its oxide ionic conductivity and catalytic property for oxygen reduction. Further increase in z, however, led the LSCF system into a coexistence region with transition metal oxides. In the wide range of P(O2), electrical property of samples 0.00≤z≤0.025 was p-type semi-conducting regardless of the z value, whereas its conductivity was strongly affected by a subtle change in z.