Structure evolution and electrostrictive properties in (Bi0.5Na0.5)0.94Ba0.06TiO3-M2O5 (MÂ =Â Nb, Ta, Sb) lead-free piezoceramics

The effects of M2O5 (M = Nb, Ta, Sb) addition on the phase transition and electrical properties of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNBT6) lead-free ceramics were studied. Results showed that M substitution into BNBT6 induced a phase transition from coexistence of ferroelectric tetragonal and rhombohedral to a relaxor pseudocubic with a significant disruption of the long-range ferroelectric order. Accordingly, large strain response of 0.42-0.43% with fatigue-free behavior, which is due to a reversible field-induced ergodic relaxor-to-ferroelectric phase transformation, was obtained at 0.5 mol% M content. Furthermore, as the compositions (x ≥ 0.06) lied deep in the pseudocubic region of the phase diagram, a high, purely electrostrictive effect with large electrostrictive coefficient Q33 of 0.020-0.024 m4/C2 was achieved. More interestingly, the obtained BNBT6-based electrostrictors showed good resistance to both long-term electric cycling (up to 106 cycles) and thermal influence (20-160 °C), rendering them suitable for high-precision positioning devices and other actuators.