Enhanced electric field-induced strain and ferroelectric behavior of (Bi0.5Na0.5)TiO3-BaTiO3-SrZrO3 lead-free ceramics

The crystal structure, electric field-induced strain (EFIS) and piezoelectric properties of lead-free SrZrO3-modified Bi0.5Na0.5TiO3-0.065BaTiO3 (BNBT-SZ100x, with x=0-10) ceramics were investigated. The X-ray diffraction analysis revealed a phase transformation from tetragonal to pseudocubic symmetry with increasing amounts of SZ. A large EFIS of 0.39% was obtained at the critical composition of BNBT-SZ2 which corresponds to a normalized strain (Smax/Emax) of 722 pm/V at a low applied field of ~5.5 kV/mm. Ferroelectric curves indicated a disruption of ferroelectric order and a decrease in the remnant polarization and coercive field. A maximum value of piezoelectric constant (197 pC/N) and electromechanical coupling coefficient (29.4%) was obtained for SZ1 ceramics. The maximum dielectric constant temperature (Tm) and depolarization temperature (Td) shifted towards lower temperatures and curves became more diffuse with increasing amounts of SZ. The results indicate that BNBT-SZ100x ceramics can be promising candidates for lead-free actuators.