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. [Display omitted] •The surface breakdown strength of the epoxy composite with Yttrium doped BiFeO3 particles increases by up to 111% with optimal filler concentration.•The polarization response of the nanocomposite to an external field was simulated to explain the reasons for the dielectric variations.•These results provide evidence for ETPR theory, which has been disputed for nearly 30 years.