Origin of large piezoelectricity in BF-BT based multiphase ferroelectrics

Bismuth ferrite-barium titanate (BF-BT) based ferroelectrics with multi-phase coexistence exhibit promising piezoelectricity, while whose physical mechanism of property enhancement is poorly understood. In the present work, the Rayleigh law, in-situ electric field dependent synchrotron X-ray diffraction and ex-situ piezo-response force microscopy were utilized to gain insight into the property and structure evolution characteristics under electric fields. Extrinsic contribution from domain wall motion was regarded as the major determiner in piezoelectricity of the 0.69Bi1.05Fe0.99Sc0.01O3-0.3BaTiO3-0.01Bi1.05(Zn0.5Hf0.5)O3 ferroelectrics with rhombohedral and pseudo-cubic phase coexistence, different from those proposed structural origins in BF-BT based relaxor ferroelectrics (with high BT content) with large strain response. By analyzing the property discrepancy between unpoled and poled samples, the enhanced polarization and electro-strain in poled ceramics were attributed to the activated domain state induced by the direct current pre-poling.