Effect of Sm₂O₃ on the microstructure and piezoelectric properties of 0.28PIN-0.32PZN-0.1PZ-0.3 PT ceramics

In this work, Sm₂O₃-doped 0.28PIN-0.32PZN-0.1PZ-0.3PT ceramics were synthesized by solid-state method. We systematically examined the influence of Sm₂O₃ concentration on the microstructure and electrical properties of the resulting samples. X-ray diffraction analysis indicated that all compositions retained the perovskite structure, with a minor pyrochlore phase emerging at higher Sm₂O₃ levels. Increasing Sm₂O₃ content promoted a phase transition from rhombohedral to tetragonal symmetry, causing samples to depart from the morphotropic phase boundary (MPB). The enhanced tetragonal fraction led to greater lattice distortion, hindering domain switching and thereby reducing piezoelectric performance. Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) characterization elucidated the mechanism by which an optimal Sm₂O₃ doping (0.5 mol %) improved piezoelectricity: at this concentration, the piezoelectric coefficient (d₃₃) reached 650 pC/N, the electromechanical coupling factor (k_p) was 0.54, and the Curie temperature (T_c) increased to 267 °C. These findings provide insight into extending the operational temperature range of piezoelectric ceramics for practical applications.