Single-ionized-oxygen-vacancy-related dielectric relaxation in Bi _3.25La_0.75Ti₃O₁₂ ferroelectric films

The dielectric and conductive properties of Bi3.25 La0.75 Ti O3 ferroelectric films were investigated in the temperature range of 25 °C-600 °C. A dielectric peak with a relaxation-type characteristic was observed around 400 °C. This peak can be greatly suppressed or eliminated by high sintering temperature or annealing in an oxygen atmosphere (O2), and induced again by annealing in a reducing atmosphere (N2). The activation energy of dielectric relaxation and the characteristic relaxation time are estimated to be 1.89 eV and 1.08× 10-14 s, respectively. In the corresponding temperature region, activation energy of conductivity is 0.65 eV. The mechanism of this dielectric anomaly is discussed.