Doping strategies towards acceptor-doped barium zirconate compatible with nickel oxide anode substrate subjected to high temperature co-sintering

Protonic ceramic fuel cells (PCFCs) are attractive next-generation fuel cells working at intermediate temperature (450–700 °C). Currently, the most common method to produce PCFCs is based on co-sintering anode-supported half cells composed of thin BaZr0.8Y0.2O3-δ (BZY20) electrolyte layers and thick NiO anode substrates. However, the BZY20 electrolyte reacts with NiO at the high temperature during co-sintering (1400–1600 °C), leading to significant loss of dopants in the electrolyte and thereby degradation in the conductivity. With the aim to improve the chemical compatibility between the BaZrO3-based electrolyte and NiO, in this work, we annealed the mixture of NiO and BaZrO3 doped with different dopants, and found that good compatibility was obtained between NiO and BaZr0.8Yb0.2O3-δ or BaZr0.8Tm0.2O3-δ at 1500 °C, and NiO and BaZr0.8Yb0.2O3-δ at 1350 °C. Furthermore, BaZr0.8Y0.1Yb0.1O3-δ and BaZr0.8Y0.12Yb0.08O3-δ also showed good chemical compatibility with NiO at 1350 and 1500 °C. Then, the half cells using the BaZrO3 electrolyte doped with Y and Yb were fabricated, and the ionic conductivities of the electrolytes implemented into the co-sintered half cells were measured directly in wet hydrogen. The results revealed that BaZr0.8YxYb0.2-xO3-δ (x = 0.10, 0.12, 0.13) showed higher conductivity than that of BaZr0.8Y0.2O3-δ, and BaZr0.8Y0.1Yb0.1O3-δ exhibited the highest conductivity among the three Y and Yb co-doped samples studied in this work.