Electron Paramagnetic Resonance Study on Oxygen Vacancies and Site Occupations in Mg-Doped BaTiO Ceramics.

Nominal (BaMg)TiO ( = 0.015) (BM1T) and (BaMg)TiO ( = 0.03-0.20) (BMT) ceramics were prepared by the mixed-oxide route at sintering temperatures (T) of 1200-1400 °C and 1200 °C, respectively. The solubility limit of Mg in BMT was determined by XRD to be = 0.05, and evidence was found for occupation of the A site by Mg. Electron paramagnetic resonance (EPR) was employed as a key technique to investigate the effect of T on oxygen vacancies in BM1T. The structure of BM1T changed from pseudocubic at = 1200 °C to tetragonal at 1300 °C to mixed phases of hexagonal and tetragonal at 1400 °C. When ≥ 1300 °C, a = 1.956 EPR signal was observed at = -188 °C and assigned as ionized oxygen vacancies. Mg exhibited amphoteric behavior of substituting for the double cation sites. When = 1400 °C, B-site Mg and oxygen vacancies mainly existed in the hexagonal phase and A-site Mg was dominant in the tetragonal phase. The higher tan was attributed to the higher concentrations of oxygen vacancies and Ti in the hexagonal phase.