Dielectric relaxation of oxygen vacancies in dy-doped BaTiO3

The dielectric properties of Ba(Ti1-xDyx)O3-x/2 were studied at various Dy contents (x = 0 0.02) as a function of temperature and frequency. The Curie temperature (TC) shifted to lower temperatures with increasing Dy content by -13.2 .deg. C/mol%. The unit cell volume increased with increasing Dy content (x) whereas the tetragonality (c/a ratio) decreased accordingly. The dielectric loss (tanδ) peaks shifted to higher frequencies with increasing Dy content and showed a thermally activated process. The loss peaks (tanδ) moved to higher frequencies with increasing temperature. The activation energies were estimated in two temperature regions, 0.44 - 0.63 eV at 150 - 250 .deg. C and 0.94 - 1.06 eV at 300 - 500 .deg. C. The activation energies at higher temperatures could be due to the extended motion of oxygen vacancies and to the energy for the swing motion around the defect center (Dy'Ti), which were estimated to be 0.41 - 0.50 eV at 0.001 < x < 0.02.