Quenching effects on piezoelectric properties and depolarization temperatures of (Bi0.5Na0.5)TiO3-based solid solution systems

Lead-free ferroelectric and piezoelectric ceramics, (Bi0.5Na0.5(1-x)Li-0.5x)TiO3 and (1-y)(Bi0.5Na0.48Li0.02)TiO3-yBaTiO(3) (abbreviated as BNLT100x and BNLBT4-100y, respectively), were fabricated by a quenching procedure after sintering, and then their electrical properties were investigated with the aim of increasing their depolarization temperature T-d. From the measurements by a resonance-antiresonance method, the electromechanical coupling factors k(33) of BNLT100x and BNLBT4-100y were exactly the same after the quenching treatment as compared with the nonquenched one. The T-d of all BNLT100x quenched from 1100 degrees C reached around 240 degrees C, and they are almost 60 degrees C higher for x = 0, 0.02, 0.04, and almost 80 degrees C higher for x = 0.08 than those of nonquenched ceramics. We also found, from the measurement on BNLBT4-100y quenched from 1100 degrees C, that the T-d values were enhanced to higher temperature by the quenching treatment, even in the case of rhombohedral side (100y < 6), tetragonal side (100y > 6), and MPB composition (100y = 6). Moreover, we confirmed that the rhombohedrality 90-alpha and the tetragonality c/a values were enhanced by the quenching treatment. This result revealed that, even in the tetragonal symmetry, the lattice distortion (tetragonality) could also be stabilized by the quenching treatment in BNT-based solid solution ceramics. (C) 2017 The Japan Society of Applied Physics