Relaxor ferroelectricity and elevated thermal expansion behaviour of (1−x)Bi0.5Na0.5TiO3-xBaSnO3 lead-free piezoelectric ceramics

The study on piezoelectric and ferroelectric properties of sodium bismuth titanate-based materials is essential for piezoelectric electronic components. In this study, a series of lead-free relaxor ferroelectric (1− x)Bi _0.5Na _0.5TiO ₃- xBaSnO ₃ (BNT- x BS) ceramics were prepared by a conventional solid-state reaction method. The phase performance, fracture morphologies, permittivity, ferroelectricity, piezoelectricity, and thermal expansion for various BS contents ( x) were systematically studied. With an increase in x, the phase transition from R3 c to P4 bm , and the grain size marginally decreased from 1.79 to 1.51 μm. Meanwhile, the degree of dielectric relaxor and diffused phase transition improved, and the ferroelectricity and piezoelectricity initially increased and then decreased. The optimal electrical properties of P _r = 41.6 μC/cm ², d ₃₃ = 167.8 pC/N, and k _p = 0.318 were observed at x = 0.06. The paper discusses how site disorder, long-range electric dipole ordering, and grain size influence various electrical properties. The mechanism of the thermal expansion behaviour was investigated based on Born-Lande theory. This study could serve as a landmark for studying multifunctional BNT-based piezoelectric materials for potential energy-harvesting devices.