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

A novel Ba0.5Sr0.5Co0.8Fe0.2O3 − δ + LaCoO3 (BSCF + LC) composite oxide was investigated for the potential application as a cathode for intermediate-temperature solid-oxide fuel cells based on a Sm0.2Ce0.8O1.9 (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 °C and formed the final product with the composition: La0.316Ba0.342Sr0.342Co0.863Fe0.137O3 − δ at 1100 °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 ∼300 S cm−1 at a calcination temperature of 1050 °C, while the electrical conductivity of the pure BSCF was only ∼40 S cm−1. The improved conductivity resulted in attractive cathode performance. An area-specific resistance as low as 0.21 Ω cm2 was achieved at 600 °C for the BSCF (70 vol.%) + LC (30 vol.%) composite cathode calcined at 950 °C for 5 h. Peak power densities as high as ∼700 mW cm−2 at 650 °C and ∼525 mW cm−2 at 600 °C were reached for the thin-film fuel cells with the optimized cathode composition and calcination temperatures.