Microstructures and energy storage property of sandwiched BZT-BCT@Fe₃O₄/polyimide composites

In this paper, the sandwich structured polyimide composite films were studied, in which two layers of pure polyimide films were covered on both sides of BZT-BCT@Fe₃O₄/PI composite films. The result indicated that composite films with doped BZT-BCT@Fe₃O₄ had a significant performance in dielectric properties. The phases and microstructures of BZT-BCT@Fe₃O₄ and sandwiched composite films were studied by means of XRD, TEM and SEM. It was found that Fe₃O₄ was present and randomly coated on BZT-BCT. The measured dielectric properties of the composite films show great increased dielectric constant. The dielectric strength of the composite films decreases with the volume fraction raising, however, the relatively high values can be obtained when the fillers content is lower than 5 vol.%. The energy storage density increases significantly at small volume fractions, but decreases significantly at 7 vol.% due to reduced dielectric strength. On the whole, the composite films exhibit higher energy storage density and excellent discharge efficiency when the volume fraction is less than 7%, and the discharge efficiency is still higher than 85% at 265 kV/mm.