Oxygen nonstoichiometry, thermo-chemical stability and lattice expansion of La0.6Sr0.4FeO3 − δ

The oxygen nonstoichiometry of La0.6Sr0.4FeO3 − δ was measured at intermediate temperatures (773 to 1173 K) between 1 bar and the decomposition oxygen partial pressure by thermogravimetry and coulometric titration. The decomposition of the ABO3 perovskite phase was found to occur at low oxygen partial pressures (below 10− 20 bar). Using an atmosphere-controlled high-temperature XRD setup, the rhombohedral lattice parameters were obtained between 10− 4 and 1 bar at 773 to 1173 K. A phase transition from rhombohedral to cubic might be expected to occur at high temperatures and for δ near the plateau at δ = [Sr] / 2. The lattice expansion was separated into “pure” thermal and chemically induced expansion by combining the lattice parameters with the oxygen nonstoichiometry data. The linear thermal expansion was formulated with a “pure” thermal expansion coefficient of αth = 11.052 · 10− 6 K− 1 and a chemical expansion coefficient of αchem = 1.994 · 10− 2.The results were compared with previous data obtained for La0.6Sr0.4Co1 − yFeyO3 − δ with y = 0.2–0.8. La0.6Sr0.4FeO3 − δ was confirmed to show the highest thermo-chemical stability. While the chemical expansion of La0.6Sr0.4Co1 − yFeyO3 − δ seems little affected by the iron content, the thermal expansion coefficient was the lowest for La0.6Sr0.4FeO3 − δ.

► Oxygen nonstoichiometry of La0.6Sr0.4FeO3 − δ at intermediate temperatures (773–1173 K).
► High thermo-chemical stability of La0.6Sr0.4FeO3 − δ confirmed through measurement of decomposition oxygen partial pressure.
► Lattice parameter of La0.6Sr0.4FeO3 − δ measured at 773–1173 K from 10− 4 to 1 bar.
► Phase transition from rhombohedral to pseudo-cubic possibly to occur around the plateau region at high temperature.
► Linear thermal expansion formulated based on “pure” thermal and chemical expansion.