Bi0.5Na0.5TiO3-SrTiO3 lead-free piezoelectric composites with large strain under low driving fields

Lead-free (1-f)[0.73Bi0.5Na0.5TiO3-0.27SrTiO3]-f[0.75Bi0.5Na0.5TiO3-0.25SrTiO3] composites were synthesized using a conventional solid-state reaction method. The f = 0.5 composites exhibited a giant unipolar strain of 0.176 % under an ultralow driving field of 2 kV/mm, corresponding to a high normalized strain of 880 pm/V. This value is comparable with that of other macro ferroelectric/relaxor composite materials under higher electric fields and even higher than those for commercial lead-based piezoceramic materials. We believe that these bismuth sodium titanate-based composites are extremely competitive in the practical applications of actuators at low electric fields.