Boosting low-field energy storage performance in a weakly coupled lead-free ergodic relaxor of BaTiO3 -Bi (Zn2/3 Ta1/3)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/cm³ and a high energy storage efficiency of 96.51% at a low electric field of 180 kV/cm. Through combined structural analysis, dielectric characterization, local polar domain investigation, and density functional theory calculations, we establish that BZT incorporation transforms BaTiO₃ from a 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 BTbased systems, advancing the design of high-performance dielectric materials for lowfield energy storage application.