Investigation Of BSCF New Cathode For IT-SOFCs

The new mixed ionic and electronic conducting materials, Ba_xSr_1-xCo_0.8Fe_0.2O_3-δ (BSCF), were investigated as new cathode materials for IT-SOFCs. The cells with BSCF cathodes on the LSGM electrolyte, YSZ electrolyte and GDC electrolyte were fabricated and examined.The electrical conductivity of these samples decreases with Ba content in the temperature range from 200°C to 800°C. In the low temperature range, the conductivity increases with temperature and Ln(σT) varies linearly with reciprocal temperature, which indicates that electrical conduction takes place primarily by the small polaron hopping mechanism.The cells with BSCF cathode on LSGM electrolyte exhibit high performances, and the maximum power densities are all about 1.6 W/cm² using air as oxidant at 800°C, which is similar to that of a state-of-art cell with an LSM-YSZ cathode using oxygen as oxidant. The same overpotentials of different Ba-doping BSCF cathodes suggests that the diffusions of the ions between the BSCF cathodes and the LSGM electrolyte are serious.The interfacial reactions between BSCF and YSZ occur at 900°C, whereas BSCF shows a good chemical compatibility with the GDC electrolyte. A thin GDC buffering layer, as thin as about 1μm, was introduced between the BSCF cathode and the YSZ electrolyte film. The results depict a great improvement in cell performance and a significant decrease in polarization resistance after adding...