Achieving Excellent Energy Storage Properties in Fine-Grain High-Entropy Relaxor Ferroelectric Ceramics

ABO(3)-type high-entropy relaxor ferroelectric ceramics have rarely been studied in energy storage capacitor owing to easy formation of impurity phase. In this work, single phase (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3-xmol%PbO high-entropy ceramics are fabricated and investigated. The optimal composition of x = 2.0 shows a remarkable comprehensive energy storage performance with high recoverable energy density W-rec = 8.2 J cm(-3), ultrahigh efficiency eta = 92.2%, excellent temperature stability (W-rec = 4.4 J cm(-3) +/- 4%, eta = 91% +/- 3% within the range of 25-120 degrees C), and ultrafast discharge rate t(0.9) = 5.9 mu s. Three key factors, low remnant polarization P-r originating from high-entropy enhanced relaxation degree, high maximum polarization P-m due to special electronic structure of Pb ion, and high electrical breakdown strength E-b stemming from small grain size, are responsible for the improved energy storage properties. These results provide a novel strategy of developing high-entropy ceramics to optimize electrical performances including energy storage property.