Engineering relaxors by embedding ultra-weak polar regions for superior energy storage.

Dielectric capacitors with excellent energy storage performance are essential for advanced electronic systems. Nonetheless, achieving high recoverable energy storage density (W) and efficiency (η) remains highly challenging. Here, we propose a strategy of embedding ultra-weak polar regions in the strong polar fluctuation matrix to achieve substantial enhancements of energy storage properties, which is successfully verified by preparing heterogeneous relaxors using tape-casting. Phase-field simulations confirm a fast response and recovery of polarization in this unique heterogeneity. Accordingly, the hysteresis is virtually eliminated while realizing high breakdown field strength (E) and high polarization. The appropriately fined grain size also contributes to enhancing E. Hence, a giant W of 13.2 J cm and an ultra-high η of 92.5 % are achieved, superior to other relaxors prepared by the tape-casting/repeated rolling process methods to date. This work provides a viable practical paradigm for the development of high-performance relaxors for capacitors.