Enhanced energy storage performance achieved in Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3 ceramics via domain structure and bandgap width tuning

Dielectric capacitors have attracted considerable attention owing to their excellent performance, including high charge-discharge rate as well as good temperature stability and fatigue resistance. Na0.5Bi0.5TiO3(NBT)-based ceramics are considered to be one of the most prospective lead-free dielectric materials because of their unique phase transition and relaxation characteristics. However, the energy storage performance obtained in the currently available materials is not satisfactory. We propose a synergetic optimization strategy through composition design and domain engineering in 0.74Na0.5Bi0.5TiO3-0.26Sr0.7Bi0.2TiO3 (NBSBT) ceramic, i.e., by simultaneously refining the grain size and widening the bandgap width, which facilitates a large breakdown strength and ΔP (Pm–Pr). A high dielectric constant and low remnant polarization is beneficial for obtaining improved energy storage properties. Piezoelectric force microscopy revealed that the introduction of NaNbO3(NN) disrupts the microdomains of the NBSBT ceramics and promotes the generation of polar nano-regions. An excellent energy storage density (Wrec) of 4.83 J/cm3 and a moderate efficiency (η) of 87.4% are obtained at the optimum composition of 0.85NBSBT-0.15NN. These characteristics demonstrate that (1-x)NBSBT-xNN based ceramics are promising candidate materials for high-temperature energy storage devices and provide an effective strategy for the design of next-generation dielectric capacitors.