Entropy engineering of BF-BT-based high-entropy ceramics for ultra-high energy storage performance

Dielectric capacitors are critical components in pulsed power and advanced electronic systems; however, most lead-free bulk ceramic dielectrics suffer from an intrinsically low recoverable energy density (W_rec) due to limited breakdown strength (BDS) and pronounced ferroelectric hysteresis. To overcome these limitations, an entropy engineering strategy is proposed by introducing a high-entropy perovskite oxide, Ba(Ti_0.2Zr_0.2Sn_0.2Hf_0.2Nb_0.1Sc_0.1)O₃ (BTHE), into the 0.7BiFeO₃–0.3BaTiO₃ (BF–BT) ferroelectric matrix, forming a series of BF–BT–xBTHE lead-free high-entropy ferroelectric ceramics. Structural analyses reveal that multicomponent substitution at the B-site induces severe lattice distortion and enhanced pseudo-cubic phase characteristics, leading to pronounced relaxor ferroelectric behavior and significant grain refinement. As a result, both polarization hysteresis and electrical conduction are effectively suppressed, leading to a remarkable enhancement in BDS. An ultrahigh BDS of 840 kV cm⁻¹ is achieved, giving rise to a superior W_rec of 10.55 J cm⁻³ in bulk ceramics. Furthermore, statistical analysis and phase-field simulations indicate that entropy-induced microstructural heterogeneity effectively disperses local electric fields and delays dielectric breakdown. This work demonstrates that entropy engineering offers a powerful and generalizable approach to simultaneously enhancing BDS and energy-storage performance in lead-free ferroelectric ceramics.