Abstract: Dielectric ceramics with ultrahigh power density and ultrafast charge/discharge rates are crucial components of advanced dielectric capacitors. However, enhancing their comprehensive performance remains a major challenge for cutting-edge applications. Here, a high-entropy strategy is proposed to construct multiple local distortions, including various types of oxygen octahedral tilts, highly dynamic polar nanoregions, and lattice distortions. This approach effectively delays polarization saturation, reduces energy loss, and, in conjunction with the ultrafine grains induced by the high-entropy effect, enhances mechanical properties and breakdown field. Therefore, a remarkable recoverable energy density of 9.1 J cm^-3, a high conversion efficiency of 82.7 %, and a large Vickers hardness of 8.77 GPa are simultaneously achieved in 0.73Bi_0.47Na_0.47Ba_0.06TiO₃-0.27Ca_0.7La_0.2Zr_0.15Ti_0.85O₃ lead-free high-entropy relaxors. Additionally, superior frequency and temperature stability, as well as excellent charge/discharge performance, are also obtained. These findings demonstrate that the high-entropy strategy is a promising method for designing high-performance dielectric ceramics.

Key words: Dielectric ceramic, Energy storage, Relaxor ferroelectric, Polar nanoregions, Local distortion