Dielectric, ferroelectric, and piezoelectric properties of rare earth Sm-doped 0.94 Bi0.5Na0.5TiO3-0.06 BaTiO3 lead-free ceramics

Abstract

Bi0.47-xSmxNa0.47Ba0.06TiO3 (BNT-6BT-xSm) ferroelectric ceramics with different doping contents of samarium (Sm) were prepared by solid-state reaction method. All ceramics lie in the coexistence region of the rhombohedral perovskite phase (R3c) and tetragonal perovskite phase (P4bm). When the Sm content increases, the grain growth is limited, and the average grain size is reduced from 1.69 µm (at the composition of x = 0.005) to 0.86 µm (at the composition of x = 0.05). When Sm is introduced into Bi0.5Na0.5TiO3-BaTiO3 binary system, the composition-induced local structure transition occurs, namely the transition from order to disorder. And after the introduction of Sm3+ ions, the depolarization temperature (Td) increases considerably. With the increase of the Sm content, the remnant polarization (Pr) decreases from 52 μC/cm2 to 8 μC/cm2, and the coercive field (Ec) gradually decreases from 37 kV/cm to 14 kV/cm, respectively. Under an electric field of 80 kV/cm, the maximum electric field-induced strain and corresponding normalized strain (d33*) reached 0.35% and 318 pm/V (at the composition of x = 0.03), respectively. The maximum piezoelectric coefficient (d33) is 158 pC/N (at the composition of x = 0.015), resulting from the structure transition between ferroelectric phase and anti-ferroelectric phase. Therefore, BNT-6BT-0.03Sm lead-free ferroelectric ceramic is a promising candidate of lead-based ferroelectric ceramics for piezoelectric actuators.