Preparation and properties of BaxSr1−xCoyFe1−yO3−δ cathode material for intermediate temperature solid oxide fuel cells

Abstract Ba x Sr 1− x Co y Fe 1− y O 3− δ (BSCF) materials with perovskite structure were synthesized via solid-state reaction. Their structural characteristics, electrical-conduction behavior and cathode performance were investigated. Compared to A-site elements, B-site elements show a wide solid-solution range in BSCF. The electrical-conduction behavior of BSCF obeys the small polaron-hopping mechanism. An increase of Ba or Co content in the BSCF samples results in a decrease of electrical conductivity, which is mainly attributable to the preferential existence of B 3+ rather than B 4+ in Ba- or Co-rich samples. At the same time, this leads to increases in the lattice parameter a and the number of oxygen vacancies. BSCF samples with high Ba content show a high structural stability (high oxygen-loss temperature). Ba 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3− δ and Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ materials present good thermal-cycling stability of the electrical conductivity. Compared with Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ , Ba 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3− δ exhibits a better cathode performance in a Ce 0.8 Gd 0.2 O 2− δ (GDC)-supported half cell. The cell performance can be improved by introducing a certain amount of GDC electrolyte into the BSCF cathode material.