Ferroelectric P4mm to relaxor P4bm transition and temperature-insensitive large strains in Bi(Mg0.5Ti0.5)O3-modified tetragonal 0.875Bi0.5Na0.5TiO3-0.125BaTiO3 lead-free ferroelectric ceramics

Tetragonal phase (1-x)(0.875Bi0.5Na0.5TiO3-0.125BaTiO3)-xBi(Mg0.5Ti0.5)O3 lead-free ferroelectrics were designed and fabricated by a conventional solid state route. All the specimens exhibit a tetragonal perovskite structure, and undergo a phase evolution from ferroelectric P4mm to antiferroelectric relaxor P4bm as the BMT addition increases. The critical composition x = 0.04 makes a bridge between the both tetragonal phases, and gives a large field-induced strain of 0.30% and an adequately-large electrostrictive coefficient Q33 of 0.0254 m4/C2. To be highlighted, the field-induce strain of the composition x = 0.04 shows an almost constant value over the temperature range of 18-100 °C, illustrating a temperature-insensitive behavior, which could be attributed to the widened gap between TR-E and TF-R. The temperature-insensitive large strain of the tetragonal BNT-BT-BMT composition give a promising potential for application in precision position actuators.