Comprehensive Understanding of Charge and Mass Transport in BaZr0.1Ce0.7Y0.1Yb0.1O3−δ

This work reports transport properties of BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb1711), studied during oxidation/reduction and hydration/dehydration using electrical conductivity relaxation (ECR) measurements. The oxidation/reduction displayed typical monotonic conductivity relaxation behavior, attributed to the ambipolar diffusion of oxygen vacancies () and electron-holes (), and oxygen surface exchange coefficient () were >1 order of magnitude higher than bulk diffusivities (), indicating a diffusion-controlled process. Whereas, hydration/dehydration displayed a temperature-dependent gradual transition from monotonic to non-monotonic relaxation profile. At lower temperatures, transient defect concentration profile indicated that overall hydration/dehydration involved an acid-base-type reaction, comprising the diffusion of oxygen vacancy () and proton () couples. However, at higher temperatures and high [, it involved a combination of a hydrogenation reaction (comprising component H via diffusion of and couple) and an oxidation reaction (involving component O via diffusion of and couple), thus giving rise to a two-fold non-monotonic relaxation profile. The and values for oxygen vacancies (; ) were lower than those for protons () with the respective Ea being 57.51±3.14 and 60.72±1.48 kJ∙mol-1 for oxygen-vacancies and 68.78±12.65 and 71.05±13.87 kJ∙mol-1 for protons.