Partial Conductivities and Chemical Diffusivities of Mixed Protonic–Electronic Conducting CaZr0.9Y0.1O3 − δ

The electrical properties of CaZr 0.9 Y 0.1 O 3―δ (CZY) were studied as a function of both oxygen partial pressure (P O2 ) and water vapor partial pressure (P H2O ) in the temperature range of 500―950°C and the partial conductivities of protons, holes, and oxygen vacancies were calculated from the defect model. In a wet atmosphere, CZY was a mixed conductor of protons, holes, and oxygen ions. No conduction transition from protons to holes and/or oxygen ions occurred even as temperature was increased up to 950°C. The calculated activation energy of proton transport was 1.13 eV. The standard solution enthalpy for water dissolution was best fitted with a slope of ―413 kJ/mol. The twofold conductivity relaxation behavior that was observed at 750°C during hydration/ dehydration was interpreted in terms of decoupled ambipolar diffusion of oxygen vacancies and protons by holes. The best-estimated chemical diffusivities of oxygen and hydrogen were several orders of magnitude lower than that reported for other proton-conducting perovskite oxides due to the relatively low ion conductivity of CZY. .