Remarkable energy storage performance of BiFeO₃-based high-entropy lead-free ceramics and multilayers

Electrostatic energy storage capacitors featuring fast charge-discharge capability play an indispensable role in pulsed power capacitors. However, the inverse correlation between polarization and dielectric breakdown strength (E-b) is the main obstacle limiting the access to high recoverable energy storage density (Wrec) W rec ) and high efficiency (7). In this work, we designed a series of novel (1- x )BiFeO (3- x )(Ba (0.2) S r(0.2) Ca- 0.2 Bi (0.2) Na (0.2) )TiO (3) (BFx BSCBNT, x = 0.4-1.0) high-entropy lead-free relaxor ferroelectric ceramics. The synergy of refined grain size, broadened band gap, and core-shell microstructure is well-investigated by experimental results and phase-field simulations. High polarization difference is achieved by the strengthened relaxation behavior and the dominated polar nanoregions (PNRs). Both high W rec of 6.0 J/cm(3) and 7 of 81.1 % are achieved in the BF-0.8BSCBNT ceramics. In particular, a remarkable W rec of 12.1 J/cm3 3 with a 7 of 86.1 % are obtained in the multilayer ceramic capacitors (MLCCs) fabricated from the x = 0.8 composition. Excellent temperature stability (<4.0 % in the range of 25-140 degrees C) and frequency stability (<6.2 % in the range of 1-500 Hz) are also achieved in MLCCs. The excellent energy storage performance demonstrates that high-entropy strategy is effective to develop novel lead-fee ceramics and devices for energy storage applications.