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 PO2PO2 and PH2OPH2O 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 (PO2PO2), D˜iH, was greater than that of D˜vH, i.e., the oxygen chemical diffusivity at a fixed PO2PO2, at all experimental conditions, suggesting that the hydrogen chemical diffusion is always faster than oxygen upon hydration/dehydration in the temperature range studied.

► The partial conductivities of protons, holes, and oxygen vacancies with the activation energy for transport.
► The greater hydrogen chemical diffusivity than the oxygen chemical diffusivity at a fixed oxygen partial pressure (PO2PO2).
► The faster hydrogen diffusion than oxygen upon hydration/dehydration.