Configuration-entropy effects on BiFeO₃-BaTiO₃ relaxor ferroelectric ceramics for high-density energy storage

High energy-storage capability and electric breakdown strength are critical elements in next-generation pulse-power dielectric capacitors. In this report, perovskite (Bi0.7Ba0.3)(1-x)Na-x(Fe0.7Ti0.3)(1-x)TaxO3 relaxor ferroelectric ceramics (x = 0-0.3) were tailored in terms of configuration entropy from a medium entropy of 1.21R to a high entropy of 2.07R to improve energy storage. The integration of paraelectric NaTaO3 into BiFeO3-BaTiO3 results in breaking of the long-range order and formation of multiple lattice distortions toward relaxor ferroelectric characteristics. Excellent recoverable energy densities of 9.6 J cm(-3) and 10.3 J cm(-3) with efficiencies of 77% and 68% at 350 kV cm(-1) and 550 kV cm(-1) (at 10 Hz) were achieved for x = 0.15 and 0.20, respectively. Wide operating frequency (1-100 Hz) and temperature (25 degrees C-150 degrees C) stabilities were confirmed at 300 kV cm(-1). Grain boundaries and nanoclusters play critical roles as electric barriers to suppress charge mobility and increase electric breakdown strength. This study presents a promising scheme to utilize high-configuration entropy BiFeO3-BaTiO3-based ceramics for high energy-density electrostatic capacitors.