High-Entropy Strategy Engineered Superparaelectric Critical States Enabling Superior Capacitive Energy Storage in Lead-Free Sustainable Ceramics

Abstract Dielectric ceramic capacitors with superior energy storage performance serve as core components for next-generation advanced pulsed power systems and miniaturized electronic devices. However, the performance optimization of bulk dielectric ceramics is constrained by the inherent difficulty of simultaneously achieving high polarization and high efficiency. To address this issue, we propose a high-entropy strategy to construct the superparaelectric critical state—a crossover region from superparaelectric to relaxor state—for tuning the polarization configuration. Through rational compositional design, we incorporate Sr0.7Sm0.2(Zr0.5Ta0.4)O3 linear dielectric into a tetragonal Bi0.375Na0.375Ba0.25TiO3 matrix with high dielectric permittivity and large polarization, successfully shifting the maximum dielectric constant to near room temperature, enhancing rapid domain switching, and reducing hysteresis. Multiscale structural characterization reveals that the high-entropy design introduces strong local disorder to construct dynamic polar nanodomains, enabling the concurrent achievement of both high polarization and high efficiency. Consequently, the optimized ceramic delivers superior energy storage performance, including a recoverable energy density of 8.52 J/cm3 with an ultrahigh 93.86% efficiency and decent thermal stability (25–150 °C). This work provides a viable paradigm for designing high-performance dielectric ceramics for advanced capacitive energy storage applications.