Energy storage performance in high entropy 0.88(0.5BiFeO3–0.5BaTiO3)–0.06(NaNbO3)–0.06(NaTaO3) relaxor ferroelectric ceramics

Abstract

Lead-free dielectric capacitors are critical for sustainable energy storage systems, yet their performance remains limited by their low discharge energy density and efficiency. This study investigates the energy storage performance of 0.88(0.5BiFeO₃–0.5BaTiO₃) – 0.06(NaNbO₃) – 0.06(NaTaO₃) high-entropy relaxor ferroelectric ceramics synthesized via conventional solid-state reaction. The simultaneous incorporation of antiferroelectric NaNbO₃ and paraelectric NaTaO₃ into the BFO-BTO matrix caused synergistic suppression of remanent polarization and increased breakdown strength. X-ray diffraction confirmed a dominant pseudo-cubic perovskite phase (Pm-3m at ~94%) with coexisting minor rhombohedral and orthorhombic phases, while SEM revealed dense microstructure with an average grain size of 1.02 µm. Unipolar P-E hysteresis measurements at 350 kV/cm yielded P_max = 56.76 µC/cm², W_rec = 7.70 J/cm³, W_loss = 1.90 J/cm³, and η = 80.21%. This  demonstrates the simultaneous doping of antiferroelectric and paraelectric perovskites into the BFO-BTO matrix is a viable pathway toward competitive lead-free energy storage ceramics.