High electrostrictive effect in La³⁺-doped Ba(Zr_0.2Ti_0.8)O₃ lead-free ferroelectrics

Perovskite ferroelectric ceramics with T_m (temperature corresponding to maximum dielectric permittivity ε′) around room temperature and high electrostrictive coefficient Q₃₃ are of interest to the applications in high-precision actuators, since low-hysteresis/non-hysteresis and high strain response can be generated in these materials based on a purely electrostrictive effect. In this work, undoped Ba(Zr_0.2Ti_0.8)O₃ (BZT) and La³⁺-doped Ba(Zr_0.2Ti_0.8)O₃ (BLZT) lead-free ferroelectrics were synthesized by solid state reaction method. Their dielectric and ferroelectric properties were investigated systematically with an emphasis on electrostrictive effect. With respect to increase of La³⁺ content from 0 to 1%, the T_m of BLZT decreases from 44.5 °C to 14.6 °C, and the diffuseness degree γ increases from 1.814 to 1.993. A conductive mechanism, which is prominent in undoped BZT, is inhibited drastically by introducing the La³⁺ into BZT. A high electrostrictive strain of 0.08% and a low hysteresis η (<10%) are obtained simultaneously in x = 0.25% composition at room temperature. The Q₃₃ ranges from 0.0377 m⁴/C² and 0.0537 m⁴/C². This work not only reports a high electrostrictive effect in BLZT ferroelectrics, but also provides BLZT ceramics with a potential application in high-precision actuators.