High and temperature-insensitive piezoelectric performance in the lead-free Sm-doped BiFeO3-BaTiO3 ceramics with high Curie temperature

Large sensor piezoelectric constant (d33 = 334 pC/N) and superior actuator piezoelectric constant (d33* = 552 pm/V) as well as a high Curie temperature (TC = 454 degrees C) were obtained simultaneously in the lead-free 0.67Bi1.03FeO3-0.33Ba1-xSmxTiO3 ceramics. Such an excellent and temperature-insensitive piezoelectric performance with only 10% temperature variation of piezoelectric strain at the range of 25-125 degrees C is highly desirable for real applications. The structural origin of the enhanced piezoelectric performance is mainly attributed to the morphotropic phase boundary and the highest known tetragonality (cT/aT = 1.02) in such materials. Transmission electron microscopy and electro-mechanical phenomenological theory demonstrate that the superior d33 and d33* are associated with the hybrids nanodomains (60-90 nm) and flattened thermodynamic energy profile owing to the local structure heterogeneity. These results are superior as the piezoelectric properties are temperature-independent and the material has large d33*, and high TC compared to other lead-free piezoelectric ceramics.