Effects of interfaces between adjacent layers on breakdown strength and energy density in sandwich-structured polymer composites

Design of layered structures in polymer-based dielectric composites would result in regionalized distribution of fillers which is important in determining the electrical properties of the composites. Here, BaTiO3/poly(vinylidene fluoride) (BT/PVDF, denominated as B) composite layer and pure PVDF (denominated as P) layer were stacked in five different sequences to investigate the influence of interfaces formed between adjacent layers in sandwich structure on the breakdown strength of composites. B/P/B film showed the highest breakdown strength, suggesting that breakdown strength could be simply enhanced via forming two hetero-interfaces by inserting a pure polymer layer in the composite with filler homogenously distributed. Thus; the dielectric behavior and energy storage capability of B/P/B sandwich-structured composites with various BT volume fractions were studied. The significantly improved dielectric polarization and breakdown strengths were observed in B/P/B sandwich structure, where the interfaces between adjacent layers play the crucial role. Maximum discharged energy density near breakdown field was achieved at ultralow BT loading of 1 vol%. The results highlight the benefit from structural design of multilayer composites towards high-performance pulsed power systems.