Polymorphic Heterogeneous Polar Structure Enabled Superior Capacitive Energy Storage in Lead‐Free Relaxor Ferroelectrics at Low Electric Field
Jiachen Xi, Jikang Liu, Wangfeng Bai, Shiting Wu, Peng Zheng, Peng Li, Jiwei Zhai
Abstract
Abstract High‐performance energy storage dielectrics capable of low/moderate field operation are vital in advanced electrical and electronic systems. However, in contrast to achievements in enhancing recoverable energy density ( W rec ), the active realization of superior W rec and energy efficiency ( η ) with giant energy‐storage coefficient ( W rec / E ) in low/moderate electric field ( E ) regions is much more challenging for dielectric materials. Herein, lead‐free relaxor ferroelectrics are reported with giant W rec / E designed with polymorphic heterogeneous polar structure. Following the guidance of Landau phenomenological theory and rational composition construction, the conceived (Bi 0.5 Na 0.5 )TiO 3 ‐based ternary solid solution that delivers giant W rec / E of ≈0.0168 µC cm −2 , high W rec of ≈4.71 J cm −3 and high η of ≈93% under low E of 280 kV cm −1 , accompanied by great stabilities against temperature/frequency/cycling number and excellent charging–discharging properties, which is ahead of most currently reported lead‐free energy storage bulk ceramics measured at same E range. Atomistic observations reveal that the correlated coexisting local rhombohedral‐tetragonal polar nanoregions embedded in the cubic matrix are constructed, which enables high polarization, minimized hysteresis, and significantly delayed polarization saturation concurrently, endowing giant W rec / E along with high W rec and η . These findings advance the superiority and feasibility of polymorphic nanodomains in designing highly efficient capacitors for low/moderate field‐region practical applications.