High‐Entropy Ferroelectric‐Ferroelastic Hybrid for Ultrahigh and Temperature‐Insensitive Dielectric Energy Storage

Abstract Electrostatic energy storage plays an irreplaceable role in the pulse power systems, thus the development of capacitors with ultrahigh and thermal stable energy storage properties meets the requirement of next‐generation devices. In this study, a high‐entropy ferroelectric‐ferroelastic hybrid perovskite material is successfully developed, in which the ultralow tolerance factor triggers the ordered oxygen octahedral tilting while high‐entropy effect breaks the polarization ordering. As a result, a unique hybrid architecture, ferroelastic microdomains spanning hundreds of nanometers embedded with randomly dispersed polar nanoregions of 1–3 nm, endows the ceramic with polar heterogeneity as well as lowered polarization hysteresis, delayed polarization saturation and enhanced breakdown strength owing to the large extra local elastic field from large ferroelastic distortion. Together with the thermal stable feature of ferroelastic domains, superior energy storage properties (the recoverable energy density of 15.35 J cm ⁻³ and efficiency of 90.3% @ 70 kV mm ⁻¹ ) along with outstanding thermal stability over a wide temperature range of ‐40–200 °C can be detected based on the super‐stable dielectric response with a dielectric constant of 676 and temperature coefficient of capacitance ≤ ±15% over –100–320 °C. This work opens up not only a novel field of high‐entropy ferroelastics but also new possibilities for broadening the temperature stability range of dielectric energy storage materials.