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

BaxSr1−xCoyFe1−yO3−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 B3+ rather than B4+ 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). Ba0.6Sr0.4Co0.8Fe0.2O3−δ and Ba0.5Sr0.5Co0.8Fe0.2O3−δ materials present good thermal-cycling stability of the electrical conductivity. Compared with Ba0.5Sr0.5Co0.8Fe0.2O3−δ, Ba0.6Sr0.4Co0.8Fe0.2O3−δ exhibits a better cathode performance in a Ce0.8Gd0.2O2−δ (GDC)-supported half cell. The cell performance can be improved by introducing a certain amount of GDC electrolyte into the BSCF cathode material.