Boosting low-field energy storage performance in a weakly coupled lead-free ergodic relaxor of BaTiO3–Bi(Zn2/3Ta1/3)O3

Abstract

Achieving high energy-storage density and efficiency in dielectric capacitors at low electric fields remains a critical challenge. Herein, we achieve enhanced energy storage performance in lead-free (1 − x)BaTiO₃–xBi(Zn_2/3Ta_1/3)O₃ (BT–xBZT) solid solutions, demonstrating a recoverable energy density of 1.31 J cm⁻³ and a high energy storage efficiency of 96.51% at a low electric field of 180 kV cm⁻¹. Through combined structural analysis, dielectric characterization, local polar domain investigation, and density functional theory calculations, we establish that BZT incorporation transforms BaTiO₃ from a normal ferroelectric to a weakly coupled ergodic relaxor. This transition originates from short-range ordered/long-range disordered chemical and polar structures, which simultaneously enable: (1) reduced remnant polarization via weakly coupled chemical/polar disorder-driven polar nanoregions, (2) enhanced field-induced polarization under a low field at optimal compositions (x = 0.08), and (3) improved breakdown strength from refined grain sizes, densified microstructures, and widened bandgaps. This work provides fundamental insights into the relaxor behavior in BT-based systems, advancing the design of high-performance dielectric materials for low-field energy storage application.