Ba0.5Sr0.5Co0.8Fe0.2O3-delta+LaCoO3 composite cathode for Sm0.2Ce0.8O1.9-electrolyte based intermediate-temperature solid-oxide fuel cells

A novel Ba0.5Sr0.5Co0.8Fe0.2O3-delta + LaCoO3 (BSCF+LC) composite oxide was investigated for the potential application as a cathode for intermediate-temperature solid-oxide fuel cells based on a Sm0.2Ce0.8HO1.9 (SDC) electrolyte. The LC oxide was added to BSCF cathode in order to improve its electrical conductivity. X-ray diffraction examination demonstrated that the solid-state reaction between LC and BSCF phases occurred at temperatures above 950 degrees C and formed the final product with the composition: La0.316Ba0.342Sr0.342Co0.863Fe0.137O3-delta at 1100 degrees C. The inter-diffusion between BSCF and LC was identified by the environmental scanning electron microscopy and energy dispersive X-ray examination. The electrical conductivity of the BSCF+LC composite oxide increased with increasing calcination temperature, and reached a maximum value of similar to 300 S cm(-1) at a calcination temperature of 1050 degrees C, while the electrical conductivity of the pure BSCF was only similar to 40 S cm(-1). The improved conductivity resulted in attractive cathode performance. An area-specific resistance as low as 0.21 ohm cm(2) was achieved at 600 degrees C for the BSCF (70 vol.%) + LC (30 vol.%) composite cathode calcined at 950 degrees C for 5 h. Peak power densities as high as similar to 700 MW cm(-2) at 650 degrees C and similar to 525 mW cm(-2) at 600 degrees C were reached for the thin-film fuel cells with the optimized cathode composition and calcination temperatures. (C) 2007 Elsevier B.V All rights reserved