Abstract
Ionic conduction and Ba 2+ :Ce 4+ site nonstoichiometry in perovskite-type oxide sinters of non-doped Ba x CeO 3− α (0.90≦ x ≦1.10) have been investigated. X-ray powder diffraction patterns of these sinters indicated that the specimens with 0.95≦ x ≦1.10 were a single phase of orthorhombic perovskite-type BaCeO 3 , while the sinter with x =0.90 was a mixed phase of perovskite and CeO 2 impurity. The conduction properties of the specimens with 0.95≦ x ≦1.05 were studied electrochemically in the temperature range of 600–1000. The conduction properties of the specimens were strongly influenced by Ba 2+ :Ce 4+ site nonstoichiometry. The specimens with excess Ba showed a predominant ionic conduction (H + +O 2− ) with ion transport number larger than 0.5 under hydrogen atmosphere, whereas they showed a poor oxide–ionic conduction (oxide–ion transport numbers <0.1) under oxidizing atmosphere. Protonic conduction in these specimens under reducing atmosphere could be confirmed by means of electrochemical hydrogen permeation. In contrast, the specimens with x ≦1.00 showed a predominant oxygen–ionic conduction (oxygen–ion transport numbers >0.8) in oxidative atmosphere, while a poor ionic conduction (ion transport numbers <0.1) was observed in hydrogen.
Published Version
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