Proton conductivity and low temperature structure of In-doped BaZrO 3

Abstract

The proton conductivity and structural features of In 3+ substituted BaZrO 3 samples, i.e., BaZr 1− x In x O 3− δ , were investigated. Rietveld analysis of low temperature (10 K) neutron powder diffraction data collected on as-prepared and deuterated samples confirmed cubic symmetry (space group Pm-3m) for all compositions. The level of oxygen vacancies refined in the as-prepared samples were in good agreement with the values expected to conserve charge neutrality, whilst an increase in oxygen occupancy, reflecting the incorporation of OD − species, was obtained for the deuterated materials. An expansion of the unit cell parameter, a, was observed as a function of In 3+ doping as well as after the deuteration reaction. The conductivity of pre-hydrated and dry samples was measured using impedance methods. For 25% In-doped BaZrO 3, the low T (300 °C) conductivity of the heating cycle of the dried sample was greater than that of the cooling cycle of the pre-hydrated sample indicating a greater number of protons in the nominally dry sample. In contrast, the conductivity values were similar at higher temperatures e.g. T > 500 °C where proton conduction is not dominant.