Enhanced electrostrictive effects in nonstoichiometric 0.99Bi 0.505 (Na 0.8 K 0.2 ) 0.5-x TiO 3 -0.01SrTiO 3 lead-free ceramics

Abstract In this work, the 0.99Bi 0.505 (Na 0.8 K 0.2 ) 0.5-x TiO 3 -0.01SrTiO 3 (BNKST(0.5-x)) nonstoichiometric ceramics with x = 0.015, 0.02 and 0.025 were synthesized by the normal solid-state sintering method. The structure, ferroelectric and electrostrictive properties of (Na, K) nonstoichiometric ceramics were investigated. The electrostrictive coefficients ( Q 33 ) increase from 0.0192 m 4 /C 2 for x = 0 stoichiometric sample to 0.027, 0.0255 and 0.0248 m 4 /C 2 for x = 0.015, 0.02 and 0.025 nonstoichiometric samples, respectively, which are comparable with that of lead-based electrostrictors. The disordered local structure and the interactions between the highly dynamic PNRs play important roles on the enhanced electrostrictive effects of nonstoichiometric samples. Furthermore, the Q 33 values of all the samples show temperature-insensitivity up to 120 °C, rendering them suitable for actuators and high-precision positioning devices. Our work may provide a new approach to quest for high-performance NBT-based lead-free electrostrictive materials by means of A-site compositional modification.