Abstract:The dielectric properties and phase transition characteristics of La₂O₃- and Sb₂O₃-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray diffraction method and scanning electron microscope was also employed to observe the surface morphologies. It is found that (La,Sb)-codoped barium strontium titanate ceramics exhibit typical perovskite structure and the average grain size decreases dramatically with increasing the content of Sb₂O₃. Both La³⁺ ions and Sb³⁺ ions occupy the A-sites in perovskite lattice. The dielectric constant and dielectric loss of barium strontium titanate based ceramics are obviously influenced by La₂O₃ as well as Sb₂O₃ addition content. The tetragonal-cubic phase transition of La₂O₃ modified barium strontium titanate ceramics is of second order and the Curie temperature shifts to lower value with increasing the La₂O₃ doping content. The phase transition of (La,Sb)-codoped barium strontium titanate ceramics diffuses and the deviation from Curie-Weiss law becomes more obvious with the increase in Sb₂O₃ concentration. The temperature corresponding to the dielectric constant maximum of (La,Sb)-codoped barium strontium titanate ceramics decreases with increasing the Sb₂O₃ content, which is attributed to the replacement of host ions by the Sb³⁺ ions.

Key words: barium strontium titanate; La₂O₃; Sb₂O₃; perovskite; ceramics; dielectric properties; phase transition