notRoles of lattice distortion in (1−x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramics

Structure property relations in (1−x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramics were investigated at x=0–10 mol %. A solid solution with either rhombohedral or tetragonal symmetry was confirmed with a morphotropic phase boundary (MPB) at x=5–7 mol %. Grains became small with increasing x possibly due to grain boundary pinning by BaBi′–BaNa•. Lattice distortion was a key factor affecting piezoelectric coefficient (d33) and depolarization temperature (Td). Both rhombohedral 90−α and tetragonal cT/aT lattice distortion became smaller toward the MPB causing poling by field and depoling by temperature to become easier subsequently resulting in higher d33 but lower Td, and vice versa.