Significantly enhanced piezoelectric properties of BaTiO₃-based ceramics with unchanged curie temperature via local chemical inhomogeneity

To meet the demand for higher piezoelectric response in advanced technologies, extensive efforts have been made in the past few decades to enhance the piezoelectricity of materials near the morphotropic phase boundary (MPB). However, the enhancement of the piezoelectricity of a material always comes at the expense of its Curie temperature (T_C), which severely restricts the operating temperature range of high-piezoelectric materials. Herein, significantly enhanced piezoelectric coefficient (d₃₃) is achieved in lead-free (Ba,Ca)(Zr,Ti)O₃ ceramics with unchanged T_C via secondary sintering treatment, where the d₃₃ increases from 550 pC/N to 710 pC/N. Transmission electron microscopic (TEM) observations and atomic-resolution high-angle annular dark-field (HADDF) images reveal that the presence of local composition fluctuations and polarization rotations in nanodomains of the sample after secondary sintering. Furthermore, the application of Rayleigh analysis, piezoresponse force microscopy (PFM) observation, and phase-field simulation methods show the key role of enhanced reversible domain wall motion in promoting the piezoelectric response induced by the enhanced local chemical inhomogeneity, which may be ascribed to the migration of oxygen vacancies. This work may provide new insights into designing piezoelectric materials with both high piezoelectricity and high Curie temperature.