Dielectric properties of SrBi2−xLaxNb2O9 (0 ≤ x ≤ 0.35) ceramics

SrBi2−xLaxNb2O9 (x = 0, 0.05, 0.1, 0.2 and 0.35) ceramics were prepared by a conventional solid-state reaction method. Their structure and dielectric properties were investigated. X-ray diffraction analysis showed that single-phase layered perovskites were obtained. A relaxor like transition was observed in SrBi2−xLaxNb2O9 with x = 0.2 and 0.35. For the specimens with x = 0.05 and 0.1, a relaxation-type dielectric loss peak was observed in the temperature range of 30–150 °C. The temperature of the maximum dielectric constant Tm decreases linearly with increasing La content. The degree of frequency dispersion ΔTm, which is the Tm difference between 10 kHz and 1 MHz, increases from 0 °C for x = 0–7 °C for x = 0.35. However, when x = 0.1, ΔTm equals −1 °C, which might be attributed to oxygen-vacancy-induced dielectric relaxation. In addition, La substitution results in a decrease in both remanent polarization and coercive field.