Ultrahigh Energy Storage Density and High Efficiency in Lead-Free (Bi 0.9 Na 0.1 )(Fe 0.8 Ti 0.2 )O 3 -Modified NaNbO 3 Ceramics via Stabilizing the Antiferroelectric Phase and Enhancing Relaxor Behavior.

Dielectric capacitors have attracted growing attention because of their important applications in advanced high power and/or pulsed power electronic devices. Nevertheless, the synergistic enhancement of recoverable energy storage density ( W rec > 10 J/cm 3 ) and efficiency (η > 80%) is still a great challenge for lead-free dielectric bulk ceramics. Herein, by introducing complex perovskite compound (Bi 0.9 Na 0.1 )(Fe 0.8 Ti 0.2 )O 3 with a smaller tolerance factor into an NaNbO 3 matrix (NN-BNFT), we have achieved and explored stable relaxor antiferroelectric ceramics with enhanced relaxor behavior. Of particular importance is the composition of 0.88NN-0.12BNFT, which exhibits a large electric breakdown strength E b of 87.3 kV/mm, an ultrahigh W rec of 12.7 J/cm 3 , and a high efficiency η of 82.5%, as well as excellent thermal reliability and an ultrafast discharge speed, resulting from the dense microstructure, the moderate dielectric constant, the reduced grain size, the dielectric loss, and the sample thickness. The outstanding energy storage properties of NN-BNFT display great promise in advanced dielectric capacitors for energy storage applications.