Effect of NiO sintering-aid on hydration kinetics and defect-chemical parameters of BaZr0.8Y0.2O3 − Δ

The influence of NiO, used as a sintering aid, on the transport properties of BaZr0.8Y0.2O3 − Δ was investigated by monitoring electrical conductivity relaxation of specimens with and without NiO during hydration in atmospheres of different oxygen activities at 700 and 800 °C. The chemical diffusivities of H and O governing the kinetics were precisely evaluated from the transient conductivity, and all the defect-chemical parameters - the two external equilibrium constants and mobilities of all the carriers, VO· ·, Hi· and h· - were determined from the steady-state equilibrium conductivity. It is found that the processing benefits afforded by NiO are accompanied by a significant reduction in ionic mobilities and hydration reaction constant. These factors, in turn, result in a smaller electrolytic regime in the presence of NiO than when it is absent.