4-inch Ternary BiFeO₃–BaTiO₃–SrTiO₃ Thin Film Capacitor with High Energy Storage Performance

BiFeO3–BaTiO3 is a promising base for developing high energy density capacitors. However, no reports have been available on fabrication of binary or even ternary BiFeO3–BaTiO3 based solid solution films via a chemical solution route since Ba2+ and Bi3+ are incompatible. Here, we developed a chemical route via alternative coating layers of relaxor ferroelectric 0.4BiFeO3-0.6SrTiO3 and paraelectric Ba0.5Sr0.5TiO3 to realize a BiFeO3–BaTiO3–SrTiO3 film with the assistance of element interface diffusion. A remarkably improved energy density of 98 J cm–3 and a high efficiency of 80% are obtained in the film with optimized layer thickness because of its large dielectric constant, high breakdown strength, and strong relaxor behavior. Of particular interest, the fabrication technique allows deposition of film over an entire 4-in. silicon wafer with good uniformity and comparable energy-storage performance. The strategy can be applicable for fabrication of large-area dielectric or other films with incompatible elements in their precursor solution.