Improved Energy Storage Properties Achieved in (K, Na)NbO3‑Based Relaxor Ferroelectric Ceramics via a Combinatorial Optimization Strategy

Abstract Although ceramic dielectric materials have been extensively explored owing to their numerous advantages, there are still obstacles in the collaborative enhancement of recoverable energy density ( W rec ) and efficiency (η). In this work, a combinatorial optimization strategy is proposed to optimize energy storage properties of (K, Na)NbO 3 ‐based ceramics, that is, drive a specific temperature region between the temperature of maximum dielectric constant and the Burns temperature to room temperature under the guidance of phase field simulation to induce the polar nanoregions, then further improve the breakdown strength by repeated rolling process. As a result, an ultrahigh W rec of 6.7 J cm −3 and a high η of 92% at 600 kV cm −1 are achieved simultaneously in the 0.85K 0.5 Na 0.5 NbO 3 ‐0.15Bi(Zn 2/3 Ta 1/3 )O 3 ceramic prepared by repeated rolling process, together with excellent temperature stability under 400 kV cm −1 over a temperature range of 25 to 150 °C, outperforming all reported (K, Na)NbO 3 ‐based energy storage ceramics. This approach should also be generalizable for designing high‐performance dielectrics for electrical energy storage applications.