The dual strategies of A-site deficiency and addition of ZnO sintering aid have been employed to optimise stability and densify the high-temperature proton conductor Ba0.95Ce0.8Y0.2O3-δ at 1200 °C (B95CYZn-1200). Structural analysis performed by Rietveld refinement based on X-ray diffraction data indicated perovskite phase with monoclinic symmetry (space group, I2/m). Raman spectroscopy revealed the presence of ZnO for material sintered at 1200 °C, which most likely partially resides in grain-boundary regions, leading to enhanced electrical transport observed by impedance spectroscopy at low temperature. Anomalous and reproducible frequency-dependent impedance behaviour below 500 °C, observed in various atmospheres, is suggested to be attributable to the varistor-type properties of ZnO. The electrical conductivity of B95CYZn-1200 in the range 500–900 °C is typical of perovskite proton conductors but with greater conductivity than both Ba-stoichiometric BaCe0.8Y0.2O3-δ and ZnO-free Ba0.95Ce0.8Y0.2O3-δ in wet O2 and N2, reaching ∼ 1.1 S m−1 at 550 °C in wet O2. Resistance to carbonate formation and mechanical breakdown was demonstrated via prolonged impedance measurements in CO2- and H2-containing atmospheres in the range 600–700 °C. © 2024 The Authors

The authors acknowledge financial support from the project PID2021-123308OB-I00, funded by MCIN/AEI (Spain) /10.13039/501100011033 and "ERDF A way of making Europe" by the European Union.

Peer reviewed