Filler-synergy route for optimising dielectric features of novel polymer-based ternary composite films bearing Fe2TiO5 pseudo-perovskite and graphite particles

Abstract High permittivity and low dielectric loss play a crucial role in enabling the applications of polymer-based composite dielectrics bearing ceramic particles in promising energy storage devices. The well-designed synergy of the two types of ceramics with varying conduction ability can effectively balance the high permittivity and low dielectric loss in composites. In this study, we optimised the dielectric properties of novel poly (vinylidene fluoride) (PVDF)/Fe2TiO5 (FTO)/graphite ternary composite films fabricated via solution casting technology. FTO pseudo-perovskite micro-particles with semiconducting features and rich ionic electric dipoles were used as the primary filler. Graphite micro-particles with high conductivity were used as an assistant filler. PVDF with rich ferroelectric domains was utilised as a polymeric matrix. High permittivity of the composites was attributed to both the mild PVDF/FTO and strong PVDF/graphite interface polarisation effects. Compared with PVDF/FTO binary composites, the ternary composites filled with low-content graphite exhibited significantly improved permittivity and slightly increased dielectric loss. Controllable low-level interface leakage conduction was responsible for the low conductivity and dielectric loss as well as the acceptable electric breakdown strength achieved in the ternary composites. The ternary composite bearing 20 wt% FTO and 0.1 wt% graphite showed a high permittivity of ~45 at 100 Hz, low dielectric loss of ~0.15 at 100 Hz, and high breakdown strength of ~225 MV m−1. We believe that this study will assist in facilitating the development of novel composite dielectrics containing semiconducting A2BO5 pseudo-perovskite ceramic fillers.