Many investigations suggest that cobalt-based perovskite cathode is one of the most competitive candidates with the most excellent electrocatalytic activity for oxygen reduction and sufficient conductivity around intermediate temperature comparing with other ABO3-type perovskite cathode based on chromium and manganese, etc. The electrocatalytic activity, thermal expansion coefficient (TEC), chemical compatibility with different types of electrolytes as well as structural stability of Cobalt-containing perovskites as cathodes for SOFCs had been widely studied, for example, La(Sr)CoO3-δ and BaCoO3-δ. In A-site ordered perovskites fast oxygen diffusion can be achieved. Base on the study of oxygen permeation rate, A-site sublattice fully occupied by Ba2+ provides the highest oxygen permeability in contrast to Sr2+and Ca2+ in La0.6A0.4Co0.6Fe0.2O3-δ (A=Ca, Sr, Ba). Unfortunately, the sensitivity to CO2 / H2O as well as the structural transition of cubic-phase to hexagonal-phase at RT limited its further application. Cheng, et.al. pointed out that the structural-stabilization can be efficaciously improved by low concentration Nb5+ doping in the B-site. Therefore, researchers made a lot of attempts on improving the structural stability and maintaining the high oxygen permeation rate by B-site doping high oxidation state cation, such as Ta, Ni, Nb, etc.
In this study, partial substitution of Fe3+ for Co4+ is aimed at reducing the TEC of BaCoO3-δ parent oxide. Ta5+ having similar ionic size with Co4+ as another dopant in B-site will help to improve the oxygen nonstoichiometry corresponding to structural stability by introducing high oxidation states cations into B-stie. BaCo0.7Fe0.2Ta0.1O3-δ (BCFT) oxide as cathode material for proton conducting IT-SOFC had been reported. It shows low cathode polarization resistance in a symmetric cell and a fair cell performance around 255 mWcm-2 fueled with humidified H2. However, the chemical compatibility and the electrocatalytic activity of BFCT as a cathode material for IT-SOFC supported by an oxygen-ion conducting electrolyte are not reported. BFCT powder was synthesized by a solid-state reaction. La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) was used as supporting electrolyte. LSGM-supported symmetrical cells were fabricated using screen-painting process. X-Ray diffraction and SEM were performed to show the crystallization (see figure. 1). TEC and symmetric cell resistance were investigated to analyze the structural stability of BCFT to be a potential candidate of cathode for IT-SOFCs. A detailed reference list can be found in the manuscript.