Domain contribution to the aging characteristics in BaTiO₃ ceramics

The domain contribution to the aging characteristics of BaTiO₃ (BTO) ceramics in a DC electric field was quantitatively investigated using microwave dielectric spectroscopy. The BTO aging effect was related to its domain size (DS): The reduction in the apparent permittivity by the DC electric field, Δϵ, increased with decreasing BTO DS. Inspection of the microwave dielectric spectra revealed that dipole polarization governed the overall aging effect regardless of the BTO DS, and that the ionic and electronic polarizations contributions were small. Substitutional loading of acceptor Mg²⁺ into the Ti⁴⁺ site decreased the BTO's DS because defect pairs consisting of Mg_Ti′′ and its counterpart V_O ^- acted as nucleation sites for new domain walls. Magnesium-loaded BTO (Mg-BTO) had smaller Δϵ values (attributed to dipole polarization) than BTO for similar DS. The Mg_Ti′′-V_O ^- defect complex effectively clamped the domain walls, thereby suppressing domain wall migration in the presence of an electric field. The measured permittivity decrease under a DC field was 423 for BTO but 246 for Mg-BTO with a similar DS, corresponding to a 41.8% improvement.