Causation of ultra-high surface insulation of Bi0.95Y0.05FeO3/epoxy composites: Simultaneous sine-variations of dielectric and trap properties with filler content

Composite dielectrics with high vacuum insulation properties are integral to today's advanced energy transmission. In this study, 5% mol Yttrium doped BiFeO3 sub-particles were synthesized by a facile sol-gel route and then were blended with epoxy resin as filler to prepare the epoxy composites (BY5FO/EP) with a wide range of filler content. The multi-electrical investigations were employed, and the results show the BY5FO/EP composites present ultra-high surface insulation performance. As the concentration of filler increases, the dielectric constant of the BY5FO/EP composites exhibited sine-shaped variations. Considering the multiple-layers of filler particles, we determined the dielectric model of composites for a wide range of filler contents by simulation. Meanwhile, the trap depths of BY5FO/EP composites were calculated according to Isothermal Surface Potential Decay, and we found the trapping stability is of sinusoidal relevance with the filler content. The simultaneous sine-variations of dielectric polarization and trap depth lead to the vacuum surface breakdown strength of the composite increased by 111% with the optimal filler content. The results in this paper provide a prospective strategy to realize ultra-high surface insulation in a vacuum and evidence to the applicability of the Electron Triggered Polarization Relaxation theory.