Electric-Field-Induced Phase Transformation and Frequency-Dependent Behavior of Bismuth Sodium Titanate-Barium Titanate.

The electric field response of the lead-free solid solution (1- x )Bi _0.53 Na _0.47 TiO ₃ - x BaTiO ₃ (BNT-BT) in the higher BT composition range with x = 0.12 was investigated using in situ synchrotron X-ray powder diffraction. An introduced Bi-excess non-stoichiometry caused an extended morphotropic phase boundary, leading to an unexpected fully reversible relaxor to ferroelectric (R-FE) phase transformation behavior. By varying the field frequency in a broad range from 10 ^-4 up to 10 ² Hz, BNT-12BT showed a frequency-dependent gradual suppression of the field induced ferroelectric phase transformation in favor of the relaxor state. A frequency triggered self-heating within the sample was found and the temperature increase exponentially correlated with the field frequency. The effects of a lowered phase transformation temperature T _R-FE , caused by the non-stoichiometric composition, were observed in the experimental setup of the freestanding sample. This frequency-dependent investigation of an R-FE phase transformation is unlike previous macroscopic studies, in which heat dissipating metal contacts are used.
Competing Interests: The authors declare no conflict of interest.