Synthesis, microstructure and dielectric properties of antimony-doped strontium titanate ceramics

Ceramics of SrTi1−xSbxO3 (0 ≤ x ≤ 0.015) composition were prepared by solid state reaction. Samples were obtained after sintering in air at 1300 and 1400 °C, respectively, with a soaking time of 3 h. Even at 1000 °C, XRD data show single phase compositions for all samples studied. Above a critical Sb proportion (x = 0.0075) the microstructure changes and an abnormal grain growth process starts to occur. Besides, electrical measurements performed at 500 Hz frequency revealed that the dielectric losses start to decrease and the interfacial polarization increases, leading to the increase of the overall effective permittivity, up to a maximum value of ∼4500 for x = 0.01. The microstructure feature mentioned, as well as the dielectric behaviour are correlated with the change of the supplementary charge compensation induced by Sb5+ donor dopant, from an electronic mechanism toward an ionic (by Sr vacancies) one.