Excellent energy storage properties with ultrahigh W_rec in lead-free relaxor ferroelectrics of ternary Bi_0.5Na_0.5TiO₃-SrTiO₃-Bi_0.5Li_0.5TiO₃ via multiple synergistic optimization

Advanced energy storage capacitors play important roles in modern power systems and electronic devices. Next-generation high/pulsed power capacitors will rely heavily on eco-friendly dielectric ceramics with high energy storage density (W-rec), high efficiency (eta), wide work temperature range and stable charge-discharge ability, etc. Lead-free Bi0.5Na0.5TiO3 (BNT) based relaxor ferroelectric (RFE) ceramics are considered as one of the most promising candidates for energy storage capacitors. However, the application fields of them are greatly limited by their relatively low W-rec (generally <5 J/cm(3)). In this paper, excellent energy storage properties characterized by a great breakthrough in W-rec are achieved in a novel BNT system, (1-x)BNT-x(0.7SrTiO(3)-0.3Bi(0.5)Li(0.5)TiO(3))+0.5 at.%Nb2O5 (x = 0, 0.1, 0.2, 0.3, 0.4), by synergistically constructing highly dynamic polar nanoregions (PNRs) and nanodomains, ultrafine grains (submicron size) and intrinsic conduction. Of great importance, the x = 0.4 ceramic exhibits an ultrahigh W-rec of 8.63 J/cm(3) as well as a high efficiency (eta) of 89.6 % under a giant electric field of 520 kV/cm, due to coexistence of ultrahigh polarization difference (Delta P=P-max -P-r) and high dielectric breakdown electric strength (E-b). Furthermore, excellent temperature stability (20-180 degrees C), frequency stability (1 - 500 Hz), and cycling stability (1 - 10(5) times) with the variation of W-rec < +/- 4 % and eta < +/- 3 % are also found in the x = 0.4 ceramic. These results demonstrate that it is a very promising lead-free dielectric capacitor with enormous energy storage applications.