Polaron relaxation associated with the localized oxygen vacancies in Ba_0.85Sr_0.15TiO₃ ceramics at high temperatures

The temperature and frequency dependences of dielectric properties of barium strontium titanate [Ba_0.85Sr_0.15TiO₃ (BST15)] ceramics have been investigated. The dielectric relaxation behavior above 180 °C was observed in BST15 ceramics with broad dielectric peaks. The contribution of dc conduction and universal dielectric response to the relaxation has been studied. In contrast to typical ion conductor such as La₂Mo₂O₉, the extent of dielectric dispersion shows the similar temperature dependence characteristic. Polaron theory indicates that the relaxation in BST15 ceramics at high temperatures is associated with the hopping localized oxygen vacancies.