Origin of large recoverable strain in 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 near the ferroelectric-relaxor transition

Piezoceramics of composition 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 demonstrate large recoverable strain at elevated temperature (T > 75 °C), which is absent at room temperature. In situ neutron diffraction was used to measure changes in the crystallographic and domain structures during electric field application at temperatures ranging from 25 °C to 100 °C. Quantitative evaluation of the ferroelastic domain volume fraction in the field-induced phases enabled calculation of the strain contribution from non-180° domain switching. The large recoverable strain is shown to be associated with the reversible nature of the phase transformation. These findings have implications to additional BNT-xBT-based composition and other relaxor ferroelectrics.