Origin of superior energy storage performance in antiferroelectric relaxors

Antiferroelectric relaxors (AFR) have attracted increasing attention for their potential to achieve large energy storage density and high efficiency simultaneously. However, the underlying mechanism behind their superior energy storage performance remains unclear. In this study, we establish a phase-field model of a doped antiferroelectric (AFE) systems by taking into account of the nanoscale compositional heterogeneity induced by random distribution of point defects as well as the associated local electric fields and local phase transition temperature variation. It is found that as the normal AFE transforms to AFR with defect concentration increasing, both the energy storage density and efficiency of the material increases, which is consistent with experimental results. The large energy storage density and high efficiency of AFR is ascribed to the “late” polarization saturation upon increasing external electric field and “early” depolarization initiation upon decreasing electric field due to the existence of larger local electric fields in directions nearly opposite to external fields in AFR materials, which leads to more elongated polarization-applied electric field loops. It is further found that although ferroelectric relaxors (FR) also have large local electric fields, the energy storage density is larger in AFR materials as compared to FR materials because the additional force to restore antiparallel polarization alignments inherent in AFR materials make the polarization saturation later and depolarization initiation earlier in AFR, leading to more elongated polarization-applied electric field loops. This study unravels the origin of high energy storage density of AFR and could provide theoretical guide to design high-performance energy storage materials.