The influence of non-stoichiometry, deviation of Sr/Ce from unity, on conduction properties in SrCeO3 was investigated and compared with that in BaCeO3. In SrxCeO3-α, single phase of samples was confirmed for x = 0.98, 1.00, 1.02, 1.05 and 1.10. At x≤1.0, conduction was electronic in hydrogen and ionic in air. On the other hand, at x>1.0, the dominant conduction carriers were protons in hydrogen and electron holes in air. The dependence of conduction characteristic on x in SrxCeO3-α was similar to that in BaxCeO3-α, although there was small quantitative difference between two systems. This means that the A/Ce non-stoichiometry results in the similar type of defect structure in SrxCeO3-α and in BaxCeO3-α. In Sr- or Ba-poor region, the partial substitution of excess Ce for A-site in ABO3 perovskite may occur. At x > 1.0, the substitution of excess Sr or Ba for B-site may happen and this substitution leads to the introduction of the oxide ion vacancies in the lattice.
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