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Dielectric ceramic capacitors with ultrahigh power densities are fundamental to modern electrical devices. Nonetheless, the poor energy density confined to the low breakdown strength is a long-standing bottleneck in developing desirable dielectric materials for practical applications. In this instance, we present a high-entropy tungsten bronze-type relaxor ferroelectric achieved through an equimolar-ratio element design, which realizes a giant recoverable energy density of 11.0 J·cm−3 and a high efficiency of 81.9%. Moreover, the atomic-scale microstructural study confirms that the excellent comprehensive energy storage performance is attributed to the increased atomic-scale compositional heterogeneity from high configuration entropy, which modulates the relaxor features as well as induces lattice distortion, resulting in reduced polarization hysteresis and enhanced breakdown endurance. This study provides evidence that developing high-entropy relaxor ferroelectric material via equimolar-ratio element design is an effective strategy for achieving ultrahigh energy storage characteristics. Our results also uncover the immense potential of tetragonal tungsten bronze-type materials for advanced energy storage applications. The authors present an equimolar-ratio element high-entropy strategy for designing high-performance dielectric ceramics and uncover the immense potential of tetragonal tungsten bronze-type materials for advanced energy storage applications. [ABSTRACT FROM AUTHOR]

• An ever-unadoped strategy was employed to design superparaelectric phase in AgNbO 3. • A new simple composition to obtain high ESP ceramic materials is proposed. • High W rec of 7.6 J/cm3 and E b of 522 kV/cm are obtained. Ceramics capacitors, especially featuring antiferroelectric (AFE) structure, are widely used in pulsed power electronic systems due to distinctive high-power density and external field stability. Lead-free AFE material AgNbO 3 has seized substantial research attention owing to its unique temperature driven multi-level phase transitions, and many works have greatly improved the energy storage properties by engineering these temperature-dependent phase boundaries. In this work, an ever-unadopted strategy was proposed to modulate the relaxor structure in AgNbO 3 by designing room-temperature (RT) superparaelectric phase via Bi incorporation into AN lattice matrix. Structural analysis shows M phase (space group Pbcm) evolves into O phase (space group Cmcm) with 12 mol.% Bi-substitution, breaking the long-range AFE order into polar nanoregions. Hence, an ultra-high recoverable energy density (7.6 J/cm3) and a high efficiency (79 %) are simultaneously achieved in the Ag 0.64 Bi 0.12 NbO 3 ceramics under 52.2 kV/mm. Moreover, the excellent energy storage properties are accompanied with good temperature and frequency stability, with the variation of W rec less than ± 15% (over 25–120 °C) and ± 10% (over 1–200 Hz) under 25 kV/mm, respectively. The novel approach reported herein provides a new guidance for designing AgNbO 3 -based and other AFE materials for high-performance energy storage applications. [ABSTRACT FROM AUTHOR]