Improved energy storage performance by doping linear dielectrics into lead-free NaNbO₃-based ceramics

NaNbO₃-based lead-free dielectric ceramics possess significant application prospects in the field of dielectric capacitors. However, their development is hindered by low recoverable energy storage density (W_rec) and energy storage efficiency (η). Herein, novel NaNbO₃-based ceramics, (1 – x) 0.7Na_0.97Sm_0.01NbO₃–0.3(Sr_0.7Bi_0.2)(Ti_0.8Zr_0.2)O₃–xCaTiO₃, were created by adding CaTiO₃ linear dielectric, aiming to improve their energy storage performance (ESP). The phase structure, microstructure, dielectric properties, energy storage and charge–discharge performances of the ceramics were methodically analyzed. All components of the ceramics exhibit a perovskite structure consisting of two phases: antiferroelectric P-phase (AFE P) and antiferroelectric R-phase (AFE R), with the AFE R phase increasing as x rises. All ceramic surfaces exhibit clear grain morphology. The resultant ceramics have an appropriate dielectric constant and a small dielectric loss, which are beneficial for improving breakdown field strength (E_b). Finally, at an E_b of 470 kV/cm, 0.850.7Na_0.97Sm_0.01NbO₃–0.3(Sr_0.7Bi_0.2)(Ti_0.8Zr_0.2)O₃– 0.15CaTiO₃ ceramic achieves optimal ESP: W_rec = 3.9 J/cm³, η = 72.49%. In addition, it has remarkable stability with temperature and frequency in energy storage and displays ultrafast speed in the charge–discharge process (t_0.9 = 27 ns).