Efficiently enhanced energy storage performance of Ba2Bi4Ti5O18 film by co-doping Fe3+ and Ta5+ ion with larger radius

We present an efficient strategy, that is the co-substitution of Fe³⁺ and Ta⁵⁺ ions with large radius for Ti⁴⁺ ion, to enhance energy storage performance of Ba₂Bi₄Ti₅O₁₈ film. For the films co-doped with Fe³⁺ and Ta⁵⁺ ions, the maximum polarization under the same external electric field is improved because the radius of Fe³⁺ and Ta⁵⁺ ions is larger than that of Ti⁴⁺ ion. Moreover, due to the composition and chemical disorder, the relaxor properties are also slightly improved, which can not be achieved by the film doped with Fe³⁺ ions only. What is more, for the films doped with Fe³⁺ ion only, the leakage current density increases greatly due to the charge imbalance, resulting in a significant decrease in breakdown strength. It is worth mentioning that the breakdown strength of Fe³⁺ and Ta⁵⁺ ions co-doped film does not decrease due to the charge balance. Another important point is the recoverable energy storage density of the films co-doped with Fe³⁺ and Ta⁵⁺ ions has been greatly improved based on the fact that the maximum external electric field does not decrease and the maximum polarization under the same external electric field increases. On top of that, the hysteresis of the polarization has also been improved. Finally, the co-doped films with Fe³⁺ and Ta⁵⁺ ions have good frequency and temperature stability.