Enhanced electromechanical properties of (Na1/2Bi1/2)TiO3–BaTiO3 lead-free piezoelectric ceramics through alternating current polarization

The piezoelectric and electromechanical properties of 0.94(Na1/2Bi1/2)TiO3–0.06BaTiO3 (NBT–6BT) lead-free piezoelectric ceramic by alternating current polarization (ACP) and direct current polarization (DCP) methods were studied in this work. Results indicated that the thickness-mode electromechanical coupling coefficients (kt) of the NBT–6BT which located around the morphotropic phase boundary (MPB) was significantly improved with an enhancement ratio of 28.6% from 58.1% to 74.7% after ACP compared to DCP. The ferroelectric domain structure and phase structure of the samples after ACP and DCP were investigated using piezoresponse force microscopy and X-ray diffraction, which revealed that the kt enhancement is mainly originated from the higher domain wall density boosted by the ACP.