Exceptional Energy‐Storage in Low‐Temperature Sintered BCZT‐Based Ceramics Featuring Polymorphic Relaxor Phase Coupled With Dual‐Distribution Secondary Inclusions

Environmentally friendly dielectric ceramic is a vital material utilized in energy storage capacitors, which has widespread applications in next‐generation high‐power pulse devices. However, the low energy conversion efficiency (η) originated from the polarization hysteresis loss and poor recoverable energy density (Wrec) resulted from unsatisfactory breakdown strength (Eb) are difficult to be effectively solved simultaneously. Herein, a novel strategy about polymorphic relaxor phase coupled with dual‐distribution secondary inclusions is proposed for designing low‐firing BiFeO3 modified (Ba,Ca) (Zr,Ti)O3 (BF‐BCZT) dielectric ceramics with comprehensive excellent energy storage performance. In the polymorphic relaxor phase, the polarization anisotropy is reduced, resulting in a more flattened free energy barrier and minimizing polarization hysteresis loss. Meanwhile, the characteristic of dual‐distribution secondary inclusions can reduce the average grain size and improve the insulated performance, thereby increasing the mechanical property and Eb. Accordingly, a high Wrec of ≈5.8 J cm−3 and η of ≈91.3% under a large Eb ≈570 kV cm−1 are achieved together with outstanding mechanical property (Hv = 7.58 GPa), temperature stability, frequency stability and charge‐discharge ability. This work provides a fine paradigm for designing the dielectric ceramic to meet the demanding requirements of advanced energy storage applications.