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−xNax(Fe0.7Ti0.3)1−xTaxO3 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 °C–150 °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.