Superior Energy Storage Performances of Aurivillius Relaxor Ferroelectric Films at Medium Electric Field Derived from Insert Layer Engineering

Although Aurivillius ferroelectrics with a layered perovskite-like structure have presented unique fatigue resistance and a high breakdown electric field for dielectric energy storage, there remains a pressing need to achieve superior energy storage performances at medium and low electric fields since the polar nanoregions in relaxors depress the polarization. This work designs Bi6–xLaxFeMg0.5Ti3.5O18 relaxor ferroelectric films (BLTFM-x) with significant local lattice distortions by inserting a high polarization layer and doping strategies. Large polarization and a low hysteresis response at a medium field are achieved in the BLTFM-1.00 film due to strong lattice distortions derived from the local compositional inhomogeneity caused by Ti4+, Fe3+, and Mg2+ ions and the induced multiple polar nanoregions (PNRs) by La3+ ion doping. Thereby, an energy density of 57.0 J cm–3 and an energy efficiency of 84.3% are simultaneously optimized at a medium field of 2500 kV cm–1. Moreover, the BLTFM-1.00 film maintains excellent temperature stability, frequency stability, and fatigue resistance. This work proposes a promising approach to improve energy storage performances at low to medium electric fields for relaxor ferroelectric film capacitors.