Abstract:

(Ba _0.8Sr _0.2) _1-1.5x Bi_xTiO₃ (x= 0.02，0.05，0.15，short for BSBT) ceramics were synthesized by the traditional solid state reaction method. Sintering was done at 1473 K for 2 h in air atmosphere. The structural, microstructure and dielectric properties of ceramics were investigated, in which a diffuse phase transition was exhibited in dielectric studies and a diffuse dielectric anomaly was observed in high temperature range. According to the fitting results of Curie-Weiss law, BSBT ceramics exhibited a stronger phase transition for x=0.05. Besides, grain boundary resistivity of BSBT ceramics was characterized by an impedance analysis and activation energy and the activation energy for conduction calculated. Polaron theory indicated that the relaxation in BSBT ceramics at high temperatures was associated with the hopping ions caused by oxygen vacancies. And it is suggested that the diffuse dielectric anomaly for all samples was due to a competition between the dielectric relaxation behavior and the variation of the relaxation strength.

Key words: (Ba _0.8Sr _0.2) _1-1.5x Bi_xTiO₃ ceramics; diffuse phase transition; dielectric anomaly; oxygen vacancy