Large Electric Field-Induced Strain In Bifeo3-Based Ceramics By Tuning Defect Dipoles And Phase Structure

High-performance lead-free piezoelectric materials with high Curie temperature can be used as substitutes for lead-based piezoelectric components to address serious environmental issues. In our works, 0.7Bi(1.05)Fe((1-x))(+3)Fe(x)(2+)O(3-delta-) 0.3BaTiO(3) (BF-BT-xFe(2+)) ceramics, which demonstrate outstanding large-signal piezoelectric coefficient of d(33)* = 510 p.m./V and electric field-induced bipolar strain of Delta s(p-p) = 0.34% (peak-to-peak) at 50 kV/cm. Meanwhile, optimal remanent polarization of P-r = 55.8 mu C/cm(2), piezoelectric coefficient of d(33) = 178 pC/N, and Curie temperature of T-c = 485 degrees C are achieved at x = 0.07. Of particular interesting the preferred strain is observed in BF-BT-xFe(2+) ceramics with major pseudo-cubic phase. Results showed that prior electric properties are derived from synergistic effect of defect dipoles and phase structure together with non-180 degrees domain switch. The defect dipole builds an internal electric field that favors ferroelectric domain formation and polarization. In addition, the formation of defect breaks the geometry symmetry of cubic structure.