Sintering and electrochemical performance of Y₂O ₃-doped barium zirconate with Bi₂O₃ as sintering aids

Decreasing Y₂O₃-doped barium zirconate (BZY) sintering temperature is crucial for its implementation in solid oxide fuel cells (SOFC). Bismuth oxide as sintering aid for BZY is evaluated. It is found that 3 mol% Bi₂O₃ doped BZY (BZY-3) improves its shrinkage from 10.4% to 19.02% at about 1480 °C, with the maximum shrinkage rate increasing from -0.20 mm min^-1 to -0.34 mm min^-1. The activation energy for densification is 5.40 eV for BZY-3. The SEM images confirms that it is porous for BZY without Bi₂O₃ (BZY-0), but that less small pores could be seen for BZY-3 and 5 mol% Bi ₂O₃ doped BZY (BZY-5) sintered at 1400 °C for 24 h. Bi₂O₃ addition decreases the grain boundary conductivity for BZY-3 and BZY-5 obviously, but is less significant for BZY-2. It is 1.13 × 10^-3 S cm^-1 for BZY-2 in wet hydrogen atmosphere at 600 °C sintered at 1400 °C for 24 h, nearly equal to that of BZY-0. The open circuit voltage is 0.95 V, with the ionic transport number of 0.83 for BZY-2 under SOFC operating conditions.