High-entropy assisted capacitive energy storage in relaxor ferroelectrics by chemical short-range order

Next-generation advanced high/pulsed power capacitors rely heavily on dielectric ceramics with high energy storage performance. Although high entropy relaxor ferroelectric exhibited enormous potential in functional materials, the chemical short-range order, which is a common phenomenon in high entropy alloys to modulate performances, have been paid less attention here. We design a chemical short-range order strategy to modulate polarization response under external electric field and achieve substantial enhancements of energy storage properties, i.e. an ultrahigh energy density of ~16.4 J/cm3 with markedly improved efficiency ~90% at an electric field of 85 kV/mm in Nb doped (Bi0.2Na0.2K0.2La0.2Sr0.2) TiO3 system. Atomic-scale scanning transmission electron microscopy observations show that Nb exhibits a chemical short-range order structure, with Nb enriched regions displaying ultrasmall polar nanoregions and more flexible polarization configurations, which is conducive to achieving high maximum polarization and low residual polarization. Moreover, refined grain size of ~0.25μm, suppressed oxygen vacancies and enhanced bandwidth contribute to a high breakdown field strength. These collective factors result in exceptionally high energy storage density and efficiency. This short-range order strategy is expected to enhance the functional performances in other high entropy relaxor ferroelectrics. The authors propose a strategy for designing chemical short-range ordering in high-entropy ferroelectric ceramics, where elements with chemical short-range order exhibit lower local ferroelectric potential barriers.