Effect of low-level Ca2+ substitution at perovskite B site on the properties of BaZr0.8Y0.2O3-δ

The substitution effect of 5 mol% calcium at perovskite B site was investigated systematically for yttrium doped barium zirconate, including phase structure, stability in different atmospheres, electrical conductivities and sinterability. In XRD patterns, BaZr_0.8Y_0.15Ca_0.05O_3-δ (BZYC5) powders synthesized by a citrate-nitrate combustion method show the cubic perovskite structure with a = 4.211 Å, and its characteristic diffraction peak shift toward the low-angle side compared to BaZr_0.8Y_0.2O_3-δ (BZY) indicates that Ca²⁺ occupies the B site. The sintering shrinkage measurement and SEM images display a better sintering activity of BZYC5 than BZY. In both wet hydrogen and air environment, BZYC5 exhibits a higher total conductivity than BZY, which might be attributed to the enhancement of both proton formation/transportability and sintering activity. In addition, BZYC5 remains stable after CO₂ and water vapor treatment, indicating a small amount of Ca²⁺ doping does not change the chemical stability of BZY. The anode-supported single cell with dense BZYC5 electrolyte was successfully assembled and its electrochemical properties were tested, giving a high peak power density of 218 mW cm⁻² at 700 °C. These results suggest that BZYC5 is a promising electrolyte candidate for proton-conducting SOFCs.