Defect engineering induced phase competition in BNT-based relaxor ferroelectrics for dielectric energy storage

Abstract

Dielectric capacitors are independent in advanced electronics and pulse power systems as an energy storage and conversion medium. However, achieving high energy density at a low electric field remains challenging for dielectric materials to improve the safety of integrated electronic devices. In this work, the strategy of defect engineering-induced phase competition is proposed to improve the polarization behavior and strengthen dielectric temperature stability of (Bi,Na)TiO₃ (BNT)-based relaxor ferroelectric, i.e., Na_0.325Sr_0.245Ba_0.105–1.5x□_0.5xBi_0.325+xTiO₃ (NSB_0.105–1.5x□_0.5xB_0.325+xT) ceramics by changing the ratio of Bi³⁺/Ba²⁺. A high recoverable energy density (W_rec=3.6 J/cm³) is achieved at a relatively low electric field of 160 kV/cm for x=0.06 composition together with a high dielectric constant of 3142±15% in a wide temperature range of 30–386 °C, which exceeds other lead-free dielectric ceramics at the same electric field. The results demonstrate that NSB_0.015□_0.03B_0.385T ceramics are desirable for advanced pulsed power capacitors and will push the development of defect-tuned functionality of dielectric ceramics for energy storage applications.