Multi-symmetry high-entropy relaxor ferroelectric with giant capacitive energy storage

Abstract

Relaxor ferroelectric ceramics with remarkable energy storage performance, which is dominantly determined by polarization and breakdown strength, are one of the bottlenecks for next generation high/pulsed power dielectric capacitors. Herein, we report that high-entropy composition Li2CO3-densified Bi0.2Na0.2Ba0.2Sr0.2Ca0.2TiO3 achieves a giant recoverable energy density (Wrec) of 10.7 J/cm3 and an ultrahigh efficiency (η) of 89 %. To understand the mechanism, the influence of the high-entropy effect on atomic-scale polarization configuration and macroscale electrical properties has been investigated systematically. Randomly distributed A-site ions and B-site ions form complex interactions, which lead to coexisted atomic-scale low crystallographic symmetries, and thus, high-dynamic polar nanoregions as well as “intermediate polarization”, such multiple symmetry polarization configuration ensures fast and strong polarization response. On the other hand, the high-entropy system exhibits a wide band gap, helping to reduce conductivity and delay breakdown. Moreover, stable high-entropy structure brings great advantages for enhancing the thermal/frequency stability of energy storage performance. This work not only provides a material candidate with outstanding comprehensive energy storage performance but also affirms high-entropy approach is a shortcut to optimizing functional property by multi-scale interactions between polarization, microstructure and crystal structure.