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_rec) 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_b) and high polarization. The appropriately fined grain size also contributes to enhancing E_b. Hence, a giant W_rec of 13.2 J cm^-3 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.