Effect of NiO sintering-aid on hydration kinetics and defect-chemical parameters of BaZr_(0.8)Y_(0.2)O_(3 – Δ)

Abstract

The influence of NiO, used as a sintering aid, on the transport properties of BaZr_(0.8)Y_(0.2)O_(3 – 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.

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