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 Li 2 CO 3 -densified Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO 3 achieves a giant recoverable energy density ( W rec ) of 10.7 J/cm 3 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.