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. Bi 0.5 Na 0.5 TiO 3 -based ceramics have been investigated extensively for potential energy storage applications. However, its low breakdown strength E b and high remnant polarization P r 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 0.8Bi 0.5 Na 0.5 TiO 3 -0.2NaNbO 3 - x La 2 O 3 (0.8BNT-0.2NN- x La 2 O 3 ) ceramics with superior energy storage properties to overcome above issues. It shows that the composition regulation by antiferroelectric NaNbO 3 results in improved disrupted long rang order ferroelectric domain structure, effectively promoting the formation of polar nanoregions, subsequently weakening P r and enhancing relaxation behavior. The introduction of antiferroelectric NaNbO 3 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 E b and recyclable energy storage density ( W rec ). Finally, a high W rec of 4.40 ± 0.20 J/cm 3 and η of 80.1 ± 2.1% at 450 kV/cm are obtained in 0.8BNT-0.2NN-0.07La 2 O 3 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 0.36 μs, and good fatigue endurance (10 5 cycles). The results offer useful guidance for the design of novel ceramic capacitors with comprehensive energy storage performance.