Non-monotonic conductivity relaxation of proton-conducting BaCe0.85Y0.15O3−δ upon hydration and dehydration

The electrical and relaxation properties of Y-doped barium cerate (BaCe0.85Y0.15O3−δ; BCY) were studied as a function of both P O 2 and P H 2 O in the temperature range of 600–900 °C. The partial conductivities of protons, holes, and oxygen vacancies were successfully calculated, and the activation energy determined for proton transport was 0.29 eV. Twofold non-monotonic conductivity relaxation behaviors were clearly confirmed in the temperature range of 700 ∼ 800 °C during hydration/dehydration. The hydrogen chemical diffusivity at a fixed oxygen partial pressure ( P O 2 ), D ˜ iH , was greater than that of D ˜ vH , i.e., the oxygen chemical diffusivity at a fixed P O 2 , at all experimental conditions, suggesting that the hydrogen chemical diffusion is always faster than oxygen upon hydration/dehydration in the temperature range studied.