Enhanced energy storage properties in Sr(Zn₁/₃Nb₂/₃)O₃-doped Bi₀.₅Na₀.₅TiO₃–BaTiO₃ lead-free ceramics

Abstract

In this study, the energy storage properties of (1-x)(0.94Bi₀.₅Na₀.₅TiO₃-0.06BaTiO₃)-xSr(Zn₁/₃Nb₂/₃)O₃ (BNT-BT-SZN) lead-free bulk ceramic capacitors were systematically investigated for compositions x = 0, 0.1, 0.2, and 0.3, which were improved via domain engineering. Structural and dielectric modifications induced by the SZN doping were examined using X-ray diffraction (XRD) and Raman spectroscopy, revealing a phase transition from a rhombohedral-tetragonal coexistence to a pseudo-cubic structure. This transition was accompanied by increased lattice disorder and the formation of polar nanoregions (PNRs), enhancing the relaxor ferroelectric behavior. Scanning Electron Microscope (SEM) analysis confirmed grain refinement and improved densification, particularly at x = 0.2, which contributed to an enhanced breakdown strength (BDS). Dielectric measurements displayed broadened temperature-dependent permittivity peaks and pronounced frequency dispersion, characteristic of the relaxor behavior. The optimal composition, x = 0.2, exhibited a BDS of 134.2 kV/cm, a recoverable energy density (Wrec) of 0.96 J/cm³, and an efficiency (η) of 87.27%. These improvements were attributed to the synergistic effects of suppressed long-range ferroelectric order, induced PNRs, refined microstructure, and compositional homogeneity. Overall, these results demonstrate that the 0.80[0.94BNT–0.06BT]–0.20SZN ceramics have strong potential for use in lead-free dielectric capacitors for energy storage applications. The strategic incorporation of SZN offers an effective route to enhance the dielectric reliability, relaxor behavior, and energy storage performance in BNT-based bulk systems.