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

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)O-3 (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 degrees C-120 degrees C for obtaining high thermally stable electrostrains and for understanding the effect of composition on the longitudinal electrostrictive coefficient Q(33). 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, Q(33) of BNT-xBCZT ceramics increased almost linearly from 0.0244 m(4)/C-2 to 0.0374 m(4)/C-2 when x increased from 0.1 to 0.6, suggesting a composition-dependent nature. In addition, Q(33) of pure BNT (0.0215 m(4)/C-2), which has been unavailable to date, was extracted from this linear relationship. Furthermore, we revealed that the increase in Q(33) is mainly due to the increase in the cell volume. Our results not only clarify the composition effect on Q(33) in BNT-xBCZT ceramics but also provide a way to enhance Q(33) by increasing the cell volume through appropriate doping of ions or perovskite ferroelectric compounds.