Modulation of polarization behavior in Na0.5Bi0.5(Ti,Fe)O3-based heterostructure thin films for dielectric energy storage: Defect engineering study via an artificial aging process

Abstract

Na0.5Bi0.5TiO3 (NBT)-based thin films are highly desired for energy storage owing to their high intrinsic polarization and Curie temperature under the current trend of electronic device integration and portability. However, the low energy density originating from the inferior anti-breakdown ability (EBD), as well as the limited space for improvement of the gap between maximum polarization and remanent polarization (Pm–Pr) is the main challenge for practical applications. Here, we propose a strategy to modulate polarization behavior of NBT-based heterostructure thin films. Na0.5Bi0.5(Ti0.97Fe0.03)O3 (NBFT) is taken as the basic component. Na0.5Bi0.5(Ti0.98Zr0.02)O3 (NBZT) and (Ba1-xSrx)TiO3 (BSxT, where x is set with gradient characteristics of 0, 0.1 and 0.2, respectively from near to far substrate ends) are chosen to fabricate NBFT/BSxT and (NBFT/NBZT)5/NBFT heterostructure thin films. Artificial aging process is carried out for modulating polarization behavior of both the heterostructure thin films. Time-dependent strain and defect migration are observed and analyzed, reflecting the structural relaxation characteristics of the thin films. After aging with treating, the recoverable energy storage density (Wrec) of NBFT/BSxT and (NBFT/NBZT)5/NBFT are increased from 46.78 to 66.95 J/cm3 and 66.57–67.64 J/cm3, respectively, with energy storage efficiency (η) increasing from 68.46% to 75.65% and 64.33%–70.76%, respectively at 20 kHz and room temperature. This research provides a new route to take usages of aging process for designing NBT-based thin film for dielectric energy storage.