Oxygen-vacancy-related low-frequency dielectric relaxation and electrical conduction in Bi:SrTiO3

The temperature dependence of dielectric properties and electrical conduction of (ST1-1.5xBix)TiO3 (0.0133 less than or equal to x less than or equal to 0.133) was measured from 10 to 800 K. Three sets of oxygen vacancies related dielectric peaks (peaks A, B, and C) were observed. These peaks could be greatly suppressed or eliminated by annealing the samples in an oxidizing atmosphere, and enhanced or recreated by annealing in a reducing atmosphere. The results show that the Maxwell-Wagner polarization is not the main mechanism, and the Skanavi's model also cannot be directly applied. A tentative explanation was suggested. Peak A, observed in the temperature range of 100-350 K with the activation energy for dielectric relaxation E-relaxA = 0.32-0.49 eV, is attributed to the coupling effect of the conduction electrons with the motion of the off-centered Bi and Ti ions; the conduction carriers in this temperature range are from the first ionization of oxygen vacancies (V-0). Peaks B and C are also discussed.