Superior energy-storage performance in 0.85Bi0.5Na0.5TiO3–0.15NaNbO3 lead-free ferroelectric ceramics via composition and microstructure engineering

Abstract

Dielectric energy storage materials and capacitors are one of the key components for power electronics. Although strenuous efforts have been made to explore high-performance energy storage materials, the trade-off between the high polarization and high breakdown strength limits the energy density of the materials. In this work, a composition engineering strategy has been proposed to overcome the trade-off between the polarization and the breakdown strength. We introduced (Sr_1.05Bi_0.3)ScO₃ (SBS) into 0.85Bi_0.5Na_0.5TiO₃–0.15NaNbO₃ (BNT–NN), where the Sc₂O₃ embedded in the grains constructs insulating networks to enhance the breakdown strength, while the Sc³⁺ and Sr²⁺ ions enter the BNT–NN lattices and smash the R3c domains into ferroelectric polar nanoregions, maintaining the high polarization and decreasing the remnant polarization. As a result, 0.3 SBS doped BNT–NN shows a recoverable energy density (W_rec) of 7.3 J cm⁻³, one of the highest values for lead-free ferroelectric ceramics with a desirable energy efficiency (η) of 80%. Combined with its favorable temperature and frequency stabilities and discharge ability, the SBS doped 0.85Bi_0.5Na_0.5TiO₃–0.15NaNbO₃ could be a promising material for practical energy storage applications.