High Piezoelectricity in Eco-Friendly NaNbO₃-Based Ferroelectric Relaxor Ceramics via Phase and Domain Engineering

To meet the requirements of environmental friendliness, high-performance lead-free piezoelectric materials have become important materials for next-generation electronic devices. Here, lead-free and potassium-free NaNbO₃ (NN)-based ceramics with high piezoelectric (d₃₃ = 361 ± 10 pC/N) and dielectric (ε_r = 4500) properties were obtained by tolerant preparation techniques. The excellent piezoelectric and dielectric properties can be attributed to the relaxor morphotropic phase boundaries (R-MPB) and coexisting domain regions, which are beneficial in lowering the free energy and greatly improving the dielectric response and domain switching capability. Furthermore, the d₃₃ of NaNbO₃-10Ba(Ti_0.7Sn_0.3)O₃-1.5NaSbO₃ (NN-10BTS-1.5NS) ceramics can be maintained at 350 pC/N over the range of 25-80 °C with a change rate of less than 10%, exhibiting excellent temperature stability. Based on a series of in situ characterizations, the variations of the phase and domain structures of NN-based relaxor piezoelectric ceramics with temperature are clearly demonstrated. This work not only proposes new materials for sensors and actuators but also provides an excellent strategy for designing high-performance piezoelectric ceramics through phase and domain engineering.