Achieving large electric-field-induced strain in lead-free piezoelectrics

Abstract

Lead-free piezoelectric single crystals of Fe-doped 0.95(Bi1/2Na1/2)TiO3-0.05BaTiO3 are shown to combine multiple mechanisms for high strain and an effective piezoelectric coefficient of up to 3260 pm/V. This is explained based on the analysis of superstructure reflections from diffuse synchrotron x-ray scattering. It depends on three factors: (1) the stabilization of a local tetragonal structure by (Fe’- V••O)• defect dipoles, (2) the reversible creation of a morphotropic phase boundary under field, and (3) the field-induced reversible transition between a short-range ordered relaxor and a long-range ordered ferroelectric state.