Enhancing energy storage performance of BNT-based lead-free relaxor ferroelectrics via a synergistic strategy of paraelectric substitution and high entropy engineering

The development of dielectric ceramics with high energy storage performance (ESP) is essential for the advancement of high-power capacitors and pulsed-power systems. However, achieving simultaneous improvements in both recoverable energy density ( W rec ) and energy storage efficiency ( η ) remains a significant challenge. In this study, the complementary advantages of the paraelectric CaZr 0.5 Ti 0.5 O 3 (CZT) and Bi 0.5 Na 0.5 TiO 3 (BNT) are first leveraged to synthesize the BNT-CZT (Δ S config  = 1.15R), thereby enhancing the relaxor characteristic. Subsequently, K 0.5 Na 0.5 NbO 3 (KNN) is introduced to modulate the configurational entropy (Δ S config ), yielding a series of BNT-CZT- x KNN ( x  = 0.05, 0.1, 0.15, 0.2) high-entropy ceramics (Δ S config  = 1.57R, 1.77R, 1.89R, 1.96R). This strategy effectively delays polarization saturation, while simultaneously suppressing the remnant polarization ( P r ), thereby achieving superior comprehensive ESP. Δ S config  = 1.89R ceramic achieves a high W rec of 5.75 J/cm 3 and η of 79.5%. Furthermore, the material exhibits exceptional thermal and frequency stability, with variation rates maintains below 6.2% and 4.5% across the tested ranges, respectively, while simultaneously demonstrating ultra-fast charge-discharge rates. In summary, this synergistic strategy demonstrates excellent effect in enhancing the comprehensive ESP of BNT-based relaxor ferroelectric ceramics.