Ba1−xCo0.9−yFeyNb0.1O3−δ (x = 0–0.15, y = 0–0.9) as cathode materials for solid oxide fuel cells

Perovskite oxide Ba1.0Co0.7Fe0.2Nb0.1O3−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 Ba1−xCo0.9−yFeyNb0.1O3−δ (x = 0–0.15, y = 0–0.9) have been systematically evaluated. Ba1−xCo0.9−yFeyNb0.1O3−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 TEC by A-site deficiency. The electrical conductivity and TEC of Ba0.9Co0.9−yFeyNb0.1O3−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 cm2 have been achieved at 700 °C for Ba0.9Co0.7Fe0.2Nb0.1O3−δ. The composition Ba0.9Co0.3Fe0.6Nb0.1O3−δ shows the lowest TEC value of 13.2 × 10−6 °C−1 at 600 °C and can be a potential cathode material for SOFCs.

► A-site deficiency in Ba1.0Co0.7Fe0.2Nb0.1O3−δ resulted in increased electrical conductivity. ► Conductivity and TEC of Ba0.9Co0.9−yFeyNb0.1O3−δ decrease with iron doping concentration. ► Ba0.9Co0.7Fe0.2Nb0.1O3−δ demonstrates a cathode polarization resistance of 0.07 Ω cm2 at 700 °C. ► Ba0.9Co0.3Fe0.6Nb0.1O3−δ shows a TEC value of 13.2 × 10−6 °C−1 at 600 °C.