The potential application of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) as a cathode for a proton-conducting solid-oxide fuel cell based on BaCe0.9Y0.1O2.95 (BCY) electrolyte was investigated. Cation diffusion from BCY to BSCF with the formation of a perovskite-type Ba2+-enriched BSCF and a Ba2+-deficient BCY at a firing temperature as low as 900 degrees C was observed, the higher the firing temperature the larger deviation of the A to B ratio from unit for the perovskites. Symmetric cell tests demonstrated the impurity phases did not induce a significant change of the cathodic polarization resistance, however, the ohmic resistance of the cell increased obviously. Anode-supported cells with the electrolyte thickness of similar to 50 mu m were successfully fabricated via a dual-dry pressing process for the single-cell test. Under optimized conditions, a maximum peak power density of similar to 550 and 100 mW cm(-2) was achieved at 700 and 400 degrees C, respectively, for the cell with the BSCF cathode layer fired from 950 degrees C. At 500 degrees C, the ohmic resistance is still the main source of cell resistance. A further reduction in membrane thickness would envisage an increase in power density significantly. (C) 2008 Elsevier B.V. All rights reserved.