Transitions of Ba0.5Sr0.5Co0.8Fe0.2O3-δ and La0.58Sr0.4Co0.2Fe0.8O3-δ

Abstract Mixed ionic–electronic conducting perovskites are promising candidates for use as oxygen separation membrane and cathode of solid oxide fuel cells. In the current study, electrical conductivity, magnetic susceptibility, and linear expansion coefficient of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ (BSCF) and La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ (LSCF) are measured in a wide temperature range, including room temperature and below. The properties of BSCF reveal a quite complex behaviour, exhibiting five transitions around 200, 350, 500, 800, and 1050 K, which can be related to the respective valence state and the spin-state of B-site cations as well as the oxygen non-stoichiometry, whereas those of LSCF has a simple temperature dependence, exhibiting two transitions around 250 and 800 K.