Electrochemical Properties and Intermediate‐Temperature Fuel Cell Performance of Dense Yttrium‐Doped Barium Zirconate with Calcium Addition

Although BaZr 0.8 Y 0.2 O 3−δ ( BZY ) possesses large bulk proton conductivity and excellent chemical stability, its poor sinterability and grain boundaries block proton conduction. In this work, the effect of Ca as a co‐dopant and as a sintering aid (as CaO ), on the sinterability, proton conductivity, and fuel cell performance of BZY was investigated. The addition of 4 mol% CaO significantly improved the BZY sinterability: BZY pellets with densities of 92.7% and 97.5% with respect to the theoretical density were obtained after sintering at 1500°C and 1600°C, respectively. The improved BZY sinterability by CaO addition resulted also in a large proton conductivity; at 600°C, the total conductivity of BZY– CaO was 2.14 × 10 −3 S/cm, in wet Ar . Anode‐supported fuel cells with 25 μm‐thick BZY– CaO electrolyte membranes were fabricated by a dual‐layer co‐firing technique. The peak power density of the fuel cell with a BZY– Ni /BZY–4 CaO /BZY–LSCF ( La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3−δ ) configuration was 141 mW/cm 2 at 700°C, several times larger than the reported values of BZY electrolyte membrane fuel cells sintered with the addition of CuO or ZnO , demonstrating promising features for practical fuel cell applications.