Oxygen vacancy-induced aging of Mn-doped Ba_0.8Sr_0.2TiO₃ ceramics in paraelectric and ferroelectric state

The aging properties of 0.01 mol% Mn-doped Ba_0.8Sr_0.2TiO₃ ceramics have been investigated from 30 °C to 400 °C at various frequencies. Decreases in ε′(T) of the aged sample compared to the fresh one around the tetragonal-cubic transition and in the regime of diffusion have been observed. The activation energy E_a = 1.25 eV obtained from the J-T loop at zero electric field indicates that oxygen vacancies dominate in the aging. The symmetry-conforming principle of point defects was employed to explain the time and temperature dependence of aging in the dielectric constant and double/constricted P-E loops of the samples aged in the paraelectric and ferroelectric state.