Excellent energy storage performance in Bi _0.5Na _0.5TiO ₃-based lead-free high-entropy relaxor ferroelectrics via B-site modification

Abstract

Next-generation advanced high/pulsed power capacitors urgently require dielectric materials with outstanding energy storage performance. The Bi_0.5Na_0.5TiO₃-based lead-free material exhibit high polarization, but the high remanent polarization and large polarization hysteresis limit its application in dielectric capacitors. Herein, high-entropy perovskite relaxor ferroelectrics (Na_0.2Bi_0.2Ba_0.2Sr_0.2Ca_0.2)(Ti_{1-<em>x</em>%}Zr<em>_x</em>_%)O₃ are designed by adding multiple ions in A-site and replacing the B-site Ti⁴⁺ with a certain amount of Zr⁴⁺. The newly designed system showed high relaxor feature and slim <em>P</em>-<em>E</em> loops. Especially, improved relaxor feature and obviously delayed polarization saturation were found with the increasing of Zr⁴⁺. Of particular importance is that both high recoverable energy storage density of 6.6 J/cm³ and energy efficiency of 93.5% were achieved under 550 kV/cm for the <em>x</em> = 6 ceramic, accompanying with excellent frequency stability, appreciable thermal stability and prosperous discharge property. This work not only provides a potential dielectric material for energy storage applications, but also offers an effective strategy to obtain dielectric ceramics with ultrahigh comprehensive energy storage performance to meet the demanding requirements of advanced energy storage applications.