Tunning the dielectric and energy storage properties of high entropy ceramics (Bi_0.2Na_0.2K_0.2La_0.2Sr_0.2)(Ti_1-xSc_x)O₃ by Sc-doping at B-site in perovskite structure

The (Bi_0.2Na_0.2K_0.2La_0.2Sr_0.2)(Ti_1-xSc_x)O₃ (BNKLST-xSc) high entropy ceramics (HECs) have been successfully synthesized via a citrate acid method. The effects of Sc-doping on the lattice structure, microstructural morphology, dielectric and energy-storage properties of HECs are comprehensively investigated. The results indicate that although Sc³⁺ doped at B-site does not alternate the perovskite structure of BNKLST with a single phase, it results in lattice expansion and weakened bonding in TiO₆ octahedron. The dielectric constant of BNKLST-xSc is reduced while the dielectric relaxation is enhanced with increasing Sc content x, due to the enhanced structural inhomogeneity in nano-regions. In addition, the lattice structure of BNKLST-0.2Sc exhibits ultra-high thermal stability at 30–300 °C, which achieves the maximum energy storage density of 1.094 J/cm³ with an outstanding efficiency better than 80%, accompanying by the mechanical and dielectric losses as low as ~ 10^–3. It is suggested that BNKLST-0.2Sc could be promising dielectric materials in capacitors and energy-storage devices with an excellent combination of ultrahigh power density, high energy density, thermal stability as well as low mechanical and dielectric losses.