Achieving ultrahigh energy density and ultrahigh efficiency simultaneously via characteristic regulation of polar nanoregions

The advancement of dielectric ceramic materials for capacitors with exceptional energy storage performance is an inevitable requirement for the integration and miniaturization of pulse power equipment. Due to the distinctive polarization response of polar nanoregions (PNRs), it is problematic to achieve ultrahigh recovered energy density (W_rec) and ultrahigh efficiency (η) concurrently in A-site ionic disordered (Na_0.5Bi_0.5)TiO₃ (NBT)-based relaxor ferroelectric ceramics. Through characteristic regulation of PNRs, a novel strategy for maintaining large inducible polarization and ultra-low hysteresis was proposed in this work. Finally, under 544 kV/cm, the 0.85(0.7Na_0.4K_0.1Bi_0.5TiO₃-0.3Ba_0.5Sr_0.5TiO₃)-0.15Sr(Mg_1/3Nb_2/3)O₃ composition achieves ultrahigh W_rec of 7.8 J/cm³ and ultrahigh η of 97.6%. At the same time, this ceramic material has exceptional temperature stability throughout an extensive temperature range of 30–120 °C, with W_rec remaining stable at 4.8 J/cm³ (variation less than 0.2 J/cm³) and η remaining greater than 95%. The piezoresponse force microscopy and aberration-corrected transmission electron microscopy results from different scales demonstrated the characteristic regulation of PNRs. Based on the enhanced local electric field in the RFE caused by the stronger ionic disorder, the external electric field-induced potential merger and growth of PNRs was successfully limited. This composition is predicted to be a candidate material for replacing lead-based dielectrics, and the design strategy used in this work provides fresh ideas for developing alternative lead-free dielectric ceramic materials.