Perovskite Na0.5Bi0.5TiO3: a potential family of peculiar lead-free electrostrictors

Abstract

For perovskite ferroelectric oxides, the composition-induced transition from ferroelectrics to relaxors can enhance their electrostrictive coefficient Q₃₃ remarkably, and has been attracting more and more attention in recent years. Achieving a larger electro-strain response is one of the most original driving forces for pursuing higher Q₃₃ values, while the two are often incompatible. Herein, taking the promising relaxor ferroelectric Na_0.5Bi_0.5TiO₃ (NBT) as the research object, we report the excellent electrostriction-like electro-strain behaviors (0.41% ≤ S_uni ≤ 0.46%, 25 ≤ T ≤ 125 °C; S_uni exhibits only 2.23% decline after 10⁵ cycles) together with a series of enhanced Q₃₃ values (0.029–0.047 m⁴ C⁻²). Accompanied by the reconstruction of de-coupled A–O interactions, the electric-field-induced relaxor to ferroelectric state transition contributes to the superior electro-strain behaviors, while the enhanced Q₃₃ will greatly degenerate during this transition process. In contrast to the non-hysteretic electrostriction observed in linear dielectrics, for NBT-based relaxor ferroelectrics, the peculiar coexistence of ferroelectric in-phase a⁰a⁰c⁺ and anti-phase a⁻a⁻a⁻ tiltings is suggested to contribute to the enhanced electrostriction-like behaviors observed in this work. These observations indicate that NBT-based systems can be considered as a potential family of peculiar lead-free electrostrictors for application in the field of actuators.