First-principles theoretical calculations were used to examine the interactions between oxygen vacancy (VO) and rare-earth (RE) elements in barium titanate in order to clarify the mechanism of VO trapping by RE dopants, which affects the insulating reliability of BaTiO3-based multilayer ceramic capacitors (MLCC). It was found that VO was stabilized at the first and second nearest O sites of RE at Ba site (REBa), and at the second nearest O site of RE at Ti site (RETi). The structural relaxations on bond lengths of REBa–O and RETi–O in BaTiO3, which were brought about by the existence of VO at the above sites, decrease the total energy, and thus VO was stabilized. It was revealed that the stability of VO increased with decreasing solution stability of RE dopants in BaTiO3. It was concluded that RE dopants with higher solution energy in BaTiO3 efficiently trap VO, and thus the insulation reliability of MLCC was improved.

Theoretical Study on Interactions between Oxygen Vacancy and Doped Rare-Earth Elements in Barium Titanate. A.Honda, S.Higai, Y.Motoyoshi, N.Wada, H.Takagi: Japanese Journal of Applied Physics, 2011, 50[9], 09NE01