Relation between lattice distortion and depolarization temperature in quenched (Bi_0.5Na_0.5)TiO₃-(Bi_0.5Li_0.5)TiO₃-(Bi_0.5K_0.5)TiO₃ceramics

Abstract

Lead-free piezoelectric ceramics, (1-0.04-x)(Bi0.5Na0.5)TiO3-0.04(Bi0.5Li0.5)TiO3-x(Bi0.5K0.5)TiO3 (abbreviated BNLKT4-100x), were prepared by quenching treatment after sintering, and then their electrical properties and lattice distortion were investigated for the purpose of increasing their depolarization temperature Td. The Td was ∼40 °C higher for x = 0, 0.1, and 0.18 in the rhombohedral structure and at the morphotropic phase boundary composition (MPB), and ∼80 °C higher for x = 0.3 and 0.4 in the tetragonal structure than those of normally cooled samples. The increase in Td was strongly correlated with enlargement for lattice distortion. Td and k33 for quenched BNLKT4-18 in MPB composition exhibited 0.59 °C and 223 °C, respectively. Both of Td and k33 was increased by quenching compared with previously reported values. That is, tread-off relation between Td and k33 was overcame. Moreover, Td elevated above 300 °C for quenched BNLKT4-40 showing tetragonal phase. Therefore, we experimentally revealed a strong correlation between lattice distortion and Td. The quenching is an effective of increasing Td for BNLKT solid-solution systems without the deterioration of their piezoelectric properties.