Lead-free piezoceramics have been an important research topic over the past two decades, aiming to replace Pb-based piezoceramics for sensor and actuator applications. In this study, LiNbO₃ (LN) doping was employed in (1−x)Bi_1/2(Na_0.8K_0.2)_1/2Ti_0.99Nb_0.01O₃–xLN ceramics near its morphotropic phase boundary (MPB). The composition with x = 0.02 exhibits a remarkable unipolar strain (S_uni) response, achieving a high S_uni of 0.57% and a large piezoelectric strain coefficient (d₃₃^*) of 952 pm/V under a moderate electric field of 60 kV/cm. This enhancement originates from local disorder induced by cosubstitutions at the A and B sites, which facilitates a transition from a nonergodic relaxor (NER) to an ergodic relaxor (ER) state. Comprehensive analysis indicates that the overall performance in electrostrain surpasses that of most reported lead-free ceramics. By investigating the state of polar nanoregions, including thermal evolution and the electric-field-induced phase transition, the mechanisms underlying the macroscopic strain response to the LN content have been revealed, providing valuable guidance for designing high-performance lead-free relaxor ferroelectrics for sensor and actuator applications.

In this work, highly textured 0.33Pb(Ni_1/3Nb_2/3)O₃-xPbZrO₃-(0.67–x)PbTiO₃ ceramics were fabricated via low-temperature sintering without the use of sintering aids. Though composition optimization, the textured x = 0.27 ceramics demonstrate outstanding comprehensive properties (d₃₃ = 1050 pC/N, T_c = 207 ℃, d₃₃^* = 1097 pm/V, k_p = 0.73, k₃₃ = 0.83). To elucidate the origin of the enhanced electromechanical properties, the domain configuration and lattice distortion in the textured x = 0.27 ceramics were investigated using high-angle annular dark-field scanning transmission electron microscopy. The results reveal that the crystallographic anisotropy, refined stripe domains, and atomic-scale lattice distortion heterogeneity induced by texturing collectively facilitate polarization rotation and domain wall motion. This synergistic effect leads to a flattened free-energy landscape, which enhances piezoelectric and electromechanical coupling properties without lowering the T_c. Furthermore, multilayer textured ceramics were successfully fabricated, and their strain characteristics were studied. A large strain of 0.331% was achieved under an electric field of 50 kV/cm, demonstrating its excellent potential for multilayer piezoelectric actuator applications.

With the rapid advancement of electronic devices, the demand for capacitors with high energy storage steadily increases. Researchers are constantly searching for dielectrics that possess both high energy density and high energy efficiency. Using phase-field simulations, we found that cubic phase structures exhibiting linear polarization behavior have higher energy storage potential. Based on the simulation results, Sr_0.7Bi_0.2TiO₃ relaxors are introduced into the 0.88NaNbO₃–0.12Bi(Mg_2/3Ta_1/3)O₃ matrix to stabilize the cubic phase structure while enhancing polarization strength through orbital hybridization between Bi and O. Finally, a high-energy ball milling process is utilized to refine the grain size, fully exploiting its energy storage potential. In the 0.68NaNbO₃–0.12Bi(Mg_2/3Ta_1/3)O₃–0.20Sr_0.7Bi_0.2TiO₃ composition, an energy density of 10.1 J/cm³ and an energy efficiency of 88% are achieved, along with excellent temperature stability, frequency stability, and high fatigue resistance, these results are significant for improvement of energy storage dielectrics.