Phase and domain engineering strategy for enhancement of piezoelectricity in the lead-free BiFeO_(3)-BaTiO_(3)ceramics

Lead-free BiFeO_(3)-BaTiO_(3)ceramics attract widespread attention over the last two decades due to their high Curie temperature(TC)and excellent piezoelectric performance.Here,in the Nd-modified 0.67BiFeO_(3)-0.33BaTiO_(3)ceramics,an excellent piezoelectric constant(d33)of 325 pC/N was achieved by applying a novel poling method(AC-biasþDC-bias)with a high TC of 455℃.In addition,an ultrahigh normalized piezoelectric strain(d33*¼Smax/Emax)of 808 pm/V was obtained at the normal/typical and relaxor-ferroelectrics phase boundary simultaneously with good thermal stability(Dd33*(T)z 20%)in the temperature range of 25e125℃.The piezoelectric force microscopy results show the domain miniaturization from micro to nanoscale/polar nano-regions due to local structure heterogeneity caused by Nd doping.The mechanism for the giant piezoelectric strain is attributed to the thermal quenching,nano-domains,and reverse switching of the short-range order to the long-range order under the applied electric field.The strategic design of domain engineering and a proposed model for the high piezoelectricity is successfully supported by the phenomenological relation and Gibbs free energy profile.In this work,a new lead-free single-element modified BiFeO_(3)-BaTiO_(3)ceramics was developed by applying a synergistic approach of domain engineering and phase boundary for the high-temperature piezoelectric performance.