In order to improve the understanding of the role of rare-earth dopant in BaTiO
3, the effect of microstructure and oxygen defect have been investigated on the electrical properties of polycrystalline La- and Ho-doped BaTiO
3. The BaTiO
3 doped with Ho 2at.% had the core-shell structure in each grain, while La-doped BaTiO
3 did not have the core-shell. The core-shell structure in Ho-doped BaTiO
3 consists of a ferroelectric core and a nonferroelectric shell. However, the dielectric properties of Ho-doped BaTiO
3 with core-shell structure exhibited no temperature-stability as La-doped BaTiO
3. Furthermore, the oxygen diffusion related to dielectric properties was also studied from the viewpoint of defect chemistry. The oxygen diffusion coefficients for BaTiO
3 specimens were determined by secondary ion mass spectrometry. The oxygen diffusion coefficient for La-doped BaTiO
3 was highly influenced by the amount of La-doping, while that for Ho-doped BaTiO
3 was independent of the amounts of Ho-doping.
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