Enhanced piezoelectricity in 0.7BiFeO₃-0.3BaTiO₃ lead-free ceramics: Distinct effect of poling engineering

BiFeO₃-BaTiO₃ based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature. Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering, in this work, the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy (PFM) and switching spectroscopy piezoresponse force microscopy (SS-PFM), which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale. The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature. The maximum piezoresponse (R_s), remnant piezoresponse (R_rem), maximum displacement (D_max) and negative displacement (D_neg) at 45 V and 120 °C reach 122, 69, 127 pm and 75 pm, respectively. Due to the distinct effect of poling engineering in full domain switching, the corresponding d₃₃ at 50 kV/cm and 120 °C reaches a maximum of 205 pC/N, which is nearly twice as high as that at room temperature. Studying the evolution of ferroelectric domains in the poling engineering of BiFeO₃-BaTiO₃ ceramics provides an insight into the relationship between domain structure and piezoelectric response, which has implications for other piezoelectric ceramics as well.