Evolution of dielectric and ferroelectric properties in LiTaO3 under high pressure

Abstract

In this study, the evolution of electric, dielectric and ferroelectric properties of LiTaO₃ under high pressures of up to 50 GPa has been systematically investigated by combining in situ alternate-current (AC) impedance spectroscopy, X-ray diffraction, polarization–electrical field (P–E) hysteresis loop measurements, and first-principles calculations. From AC impedance spectroscopy measurements, we found that the directional movement of Li⁺ ions in the lattice can lead to an obvious electrostrictive effect in LiTaO₃. With increasing pressure, the relative permittivity increased and reached a maximum at 37.2 GPa, where LiTaO₃ exhibited a transition from ionic conduction to electronic conduction. The P–E hysteresis loop measurements showed that ferroelectricity was significantly enhanced in the R3c phase, with saturation polarization P_s and remnant polarization P_r increased by 2.3 and 3 times, respectively, whereas the ferroelectricity vanished at pressures around 37 GPa. The pressure-driven transformation of TaO₆ octahedra into TaO₈ polyhedra induced a structural transition from the R3c phase to the Pnma phase, which was responsible for both the ionic–electronic transition and the modification of ferroelectric properties. These findings provide a fresh perspective on the mechanistic connection among ferroelectricity, electrical properties, and structural evolution in lead-free ferroelectric materials under pressure, potentially accelerating the exploration and advancement of high-performance ferroelectric materials.