Thermally stable electrostrains and composition-dependent electrostrictive coefficient Q33 in lead-free ferroelectric ceramics

Abstract The electrostrictive effect plays an important role in the electric-field-induced strain (electrostrain) of ferroelectric ceramics. This is especially true in high-electric-field regions because of the high-order coupling effect between electric-field-induced polarization and electrostrain. In this study, the electrostrictive properties of (1-x)(Bi0.5Na0.5)TiO3-x(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BNT-xBCZT, x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) ferroelectric ceramics were investigated in the temperature range 30 °C–120 °C for obtaining high thermally stable electrostrains and for understanding the effect of composition on the longitudinal electrostrictive coefficient Q33. High electrostrains (>0.2% at 60 kV/cm) with good thermal stability (variation of less than 10%) in the tested temperature range were obtained for x = 0.1. Most importantly, Q33 of BNT-xBCZT ceramics increased almost linearly from 0.0244 m4/C2 to 0.0374 m4/C2 when x increased from 0.1 to 0.6, suggesting a composition-dependent nature. In addition, Q33 of pure BNT (0.0215 m4/C2), which has been unavailable to date, was extracted from this linear relationship. Furthermore, we revealed that the increase in Q33 is mainly due to the increase in the cell volume. Our results not only clarify the composition effect on Q33 in BNT-xBCZT ceramics but also provide a way to enhance Q33 by increasing the cell volume through appropriate doping of ions or perovskite ferroelectric compounds.