Defects and dc electrical degradation in CaCu ₃Ti ₄O ₁₂ ceramics: Role of oxygen vacancy migration

An energy level of 1.12 eV is found in this paper, which is proposed to dominate the dc degradation process of CaCu ₃Ti ₄O ₁₂ ceramics at high temperature and originated by the migration of oxygen vacancy. In addition, the levels of 0.09 eV and 0.51 eV are suggested to be bulk and domain boundary relaxations, respectively, which show no apparent change after dc electrical degradation. The level of 0.66 eV is proposed to be grain boundary relaxation, which cannot be observed after degradation. The increment of permittivity after dc electrical degradation is resulted from the charges accumulation near the electrodes.