Ba_(1-x)Co_(0.9-y)Fe_yNb_(0.1)O_(3-δ) (x = 0-0.15, y = 0-0.9) as cathode materials for solid oxide fuel cells

摘要

Perovskite oxide Ba_(1-x)Co_(0.9-y)Fe_yNb_(0.1)O_(3-δ) has been reported as oxygen transport membrane and cathode material for solid oxide fuel cells (SOFCs). In this study, the effects of A-site cation deficiency and B-site iron doping concentration on the crystal structure, thermal expansion coefficient (TEC), electrical conductivity and electrochemical performance of Ba_(1-x)Co_(0.9-y)Fe_yNb_(0.1)O_(3-δ) (x = 0-0.15, y = 0-0.9) have been systematically evaluated. Ba_(1-x)Co_(0.9-y)Fe_yNb_(0.1)O_(3-δ) (x = 0-0.10, y = 0.2 and x = 0.10, y = 0.2-0.6) can be indexed to a cubic structure. Increased electrical conductivity and decreased cathode polarization resistance have been achieved by A-site deficiency. No obvious variation can be observed in TEG by A-site deficiency. The electrical conductivity and TEC of Ba_(1-x)Co_(0.9-y)Fe_yNb_(0.1)O_(3-δ) decrease while the cathode polarization resistance increases with the increase in iron doping concentration. The highest conductivity of 13.9 S cm~(-1) and the lowest cathode polarization resistance of 0.07 Ω cm~2 have been achieved at 700 ℃ for Ba_(1-x)Co_(0.9-y)Fe_yNb_(0.1)O_(3-δ) ,. The composition Ba_(1-x)Co_(0.9-y)Fe_yNb_(0.1)O_(3-δ) shows the lowest TEC value of 13.2 x 10~(-6)℃~(-1) at 600 ℃ and can be a potential cathode material for SOFCs.