Enhanced energy storage performance in Ba(Mg_1/3Nb_2/3)O₃-modified NaNbO₃-Bi(Mg_2/3Nb_1/3)O₃-SrTiO₃relaxor ceramics with high grain boundary resistivity

Sodium niobate-based antiferroelectric ceramics are widely regarded as one of the most promising lead-free materials for application in energy storage capacitors. Nonetheless, the large residual polarization and comparatively low breakdown field strength limited their energy storage performance (ESP). In this work, we have designed and synthesized a new ceramic system with the composition of 0.95(0.90NaNbO₃-0.10((1-x)Bi(Mg_2/3Nb_1/3)O₃-xBa(Mg_1/3Nb_2/3)O₃))-0.05SrTiO₃ (NN-BiMN-xBaMN-ST) through partial replacement of 0.95(0.9NaNbO₃-0.10Bi(Mg_2/3Nb_1/3)O₃)-0.05SrTiO₃ (NN-BiMN-ST) at A/B site. The structural modification effectively broke the long-range ordered state and ameliorated relaxation behavior. Additionally, grain was refined and grain boundary resistivity was enhanced in certain compositions, particularly at x = 0.2, which demonstrated the highest barrier for oxygen vacancy transition and thus reduced oxygen vacancy concentration. The synergy of these two endows NN-BiMN-0.2BaMN-ST composition with superior comprehensive ESP (W_rec = 4.49 J/cm³, η = 86.51 %, the fluctuation of W_rec < 2 % within 1–300 Hz and the fluctuation of W_rec < 17 % over 25–175 °C, P_D = 118.12 MW/cm³, C_D = 1073.78 A/cm², t_0.9 = 32.5 ns), predetermining their remarkable application potential in wide-temperature pulsed power capacitors.