Effect of SnO2 concentration on the dielectric properties of BaTiO3–(Sr1−1.5xBix)TiO3 ceramics

SnO2-doped 0.45BaTiO3–0.55(Sr1−1.5xBix)TiO3 (BT–SBT) ceramics were prepared by the conventional solid state reaction method. The effect of SnO2 concentration on the microstructures and dielectric properties has been investigated. XRD results indicate all the specimens have a perovskite structure without any secondary phases. With increasing SnO2 concentration, the maximum dielectric constant decreases with slight shift in Curie temperature and the peak in temperature spectra becomes much broader. When the SnO2 concentration is 1 mol%, the specimen exhibits a more homogeneous microstructure and an improvement of the dielectric breakdown strength compared with the undoped one. Impedance analysis was carried out to investigate the trend in activation energy with the increase of SnO2 concentration. The correlation between the dielectric breakdown strength and the difference of the activation energies of grain and grain boundary was qualitatively discussed. The accumulation of space charge was found to enhance the dielectric breakdown strength.