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 degrees C. In Ba(Ti1-xMgx)O3-x, the Curie point (T-c) shifted to lower temperatures as the Mg content (x) was increased. Dielectric loss (tan delta) peaks moved to higher frequencies with increasing Mg content (x) in the Ba(Ti1-xMgx)O3-x system (0.0005 <= x <= 0.01) at 250 degrees C, whose peaks appeared at 0.5-6.9kHz for x = 0.0005-0.01. Loss (tan delta) peaks also moved to higher frequencies with increasing temperature regardless of Mg content (x). The activation energy was estimated to be 0.46-0.53eV at 150-300 degrees C and 1.08-1.12eV at 350-450 degrees C. The activation energy at higher temperatures could be due to the extra energy required for the dissociation of the dipolar complex (Mg-Ti"-V-O(center dot center dot)) in addition to the dipolar motion of oxygen vacancies.