Relaxation Associated with Oxygen Vacancies at High Temperatures and Leakage Current in Ba x Sr1−x TiO3 Ceramics

Abstract

Ba x Sr1−x TiO3 (x = 0.7, 0.8, 0.9, 1.0) ceramics were synthesized using traditional solid state reaction methods. The structure, microstructure, ferroelectric and dielectric properties of the ceramics were investigated. X-ray diffraction results show that a pure phase was obtained. For all compositions, a sharp phase transition was observed in the dielectric data and the substitution of Ba2+ by Sr2+ gradually reduced the Curie temperature. A dielectric relaxation phenomenon was observed at high temperatures (300–550°C). From impedance measurements, the activation energy for relaxation and conduction was calculated as approximately 1 eV, which suggests that relaxation in Ba x Sr1−x TiO3 ceramics at high temperatures is associated with the short-range hopping of ions caused by oxygen vacancies. An oxygenation treatment, the variation of dielectric behaviors and activation energy verified that the oxygen vacancies were the origin of the dielectric relaxation. The leakage current of Ba x Sr1−x TiO3 ceramics may be associated with the combined effect of oxygen vacancies and the size of the largest grains.