Optimized energy storage properties of Bi0.5Na0.5TiO3-based lead-free ceramics by composition regulation

To meet the demand for miniaturization and integration of electronic and electrical equipments, developing dielectric capacitors with excellent energy storage properties is of utmost importance. Bi0.5Na0.5TiO3-based ceramics have been investigated extensively for potential energy storage applications. However, its low breakdown strength Eb and high remnant polarization Pr limit the energy storage density and efficiency (η). Therefore, we explored a synergistic design strategy of domain control and grain size adjustment via La doping to successfully synthesize 0.8Bi0.5Na0.5TiO3-0.2NaNbO3-xLa2O3 (0.8BNT-0.2NN-xLa2O3) ceramics with superior ESP to overcome above issues. It shows that the composition regulation by antiferroelectric NaNbO3 results in improved disrupted long rang order ferroelectric domain structure, effectively promoting the formation of polar nanoregions, subsequently weakening Pr and enhancing relaxation behavior. The introduction of antiferroelectric NaNbO3 effectively improves the η of the system. Moreover, the grain size is decreased and densification is enhanced after La tailoring, which is beneficial for the Eb and recyclable energy storage density (Wrec). Finally, a high Wrec of 4.40 ± 0.20 J/cm3 and η of 80.1 ± 2.1% at 450 kV/cm are obtained in 0.8BNT-0.2NN-0.07La2O3 ceramic. Besides, the sample demonstrates admirable temperature stability (25–175 °C) and frequency stability (10–100 Hz). Simultaneously, it displays stable discharge energy density, rapid discharge time of 36 μs, and good fatigue endurance (105 cycles). The results offer useful guidance for the design of novel ceramic capacitors with comprehensive energy storage performance.