Synergistic approach for enhancement of piezoelectricity in the lead-free BiFeO3-BaTiO3 ceramics

Abstract

Large piezoelectric actuator coefficient (d33*) and enhanced piezoelectric sensor coefficient (d33) with high Curie temperature (TC) are desired for real applications. In this work, a synergistic approach of bipolar cycling and donor doping strategy was applied for the enhancement of piezoelectric performance. An excellent d33 value of 382 pC/N was achieved by the novel (AC-bias and DC-bias) poling method in the lead-free Nb-modified 0.67Bi1.03FeO3-0.33BaTiO3 quenched ceramics. In addition, a large d33* of ∼ 400 pm/V has been obtained under a very low electric field of 25 kV/cm along with a high TC ≈ 473 °C. This enhanced piezoelectric performance is related to the crystal structure morphotropic phase boundary, bipolar cycling, optimum grain size (∼5 µm), maximum lattice distortion, and soft-ferroelectric effect induced by the donor doping. The small strain hysteresis, Hs ≈ 20%, and temperature-insensitive piezoelectric strain, Δd33*(T) = d33*(T)/d33*(RT) ≈ 24% suggest the accurate and precise positioning in the piezoelectric actuator devices. The simultaneously improved d33 and temperature-stable d33* with a high TC are promising results in the lead-free BFBT ceramics.