Dielectric properties Ca-substituted barium strontium titanate ferroelectric ceramics

The dielectric and ferroelectric properties of Ba_1-xSr_xTiO₃ (BST) (x = 0.10, 0.20, 0.30, 0.40 and 0.60) ceramics and Ba_1-2xSr_xCa_xTiO₃ (BSCT) (x = 0.10, 0.20, 0.30) ceramics have been investigated. The low temperature phase transitions of BST ceramics vanish after Ca²⁺ substitution while the high temperature transition is diffused and relaxed, which becomes more obvious with increasing x. Ca²⁺ substitution obviously decreases the dielectric constant maximum, K_m, of BST ceramics and changes the temperature of dielectric constant maximum, T_m, of BST ceramics. The shift of T_m in BST is attributed mainly to the Sr²⁺ and Ba²⁺ concentration. BST ceramics exhibit almost normal ferroelectric characteristics, while a typical relaxor behavior was observed in BSCT ceramics. The relaxor behavior observations may be understood by a random electric field induced domain state.