Effects of Oxygen Vacancies on Relaxation Behavior of Mg-Doped BaTiO3

The effects of oxygen vacancy on the dielectric properties of Mg-doped BaTiO3 were studied as a function of frequency in the temperature range of 150–450 °C. In Ba(Ti1-x Mg x )O3-x , the Curie point (T c) shifted to lower temperatures as the Mg content (x) was increased. Dielectric loss (tan δ) peaks moved to higher frequencies with increasing Mg content (x) in the Ba(Ti1-x Mg x )O3-x system (0.0005≤x≤0.01) at 250 °C, whose peaks appeared at 0.5–6.9 kHz for x=0.0005–0.01. Loss (tan δ) peaks also moved to higher frequencies with increasing temperature regardless of Mg content (x). The activation energy was estimated to be 0.46–0.53 eV at 150–300 °C and 1.08–1.12 eV at 350–450 °C. The activation energy at higher temperatures could be due to the extra energy required for the dissociation of the dipolar complex (Mg''Ti–VO ••) in addition to the dipolar motion of oxygen vacancies.