Tailoring the dielectric properties of silicone particles/poly(vinylidene fluoride) composites based on interface structures

To reduce the dielectric loss(tanδ) and increase the dielectric breakdown strength(E_b) of silicon particles/poly(vinylidene fluoride)(Si/PVDF) composites, two kinds of core-shell structured Si particles, i.e., Si@SiO₂ and Si@SiO₂@PS were prepared by high temperature oxidation and polystyrene(PS) coating. The FTIR, XRD and TEM measurements were used to characterize the formed shell structure. The measurements results verify the existence of SiO₂ and SiO₂@PS shells on the surface of Si. The results show that the Si@SiO₂ interlayer significantly suppresses the tanδ and reduces the leakage conductivity of the Si@SiO₂/PVDF composites compared with Si/PVDF composites, and the double-shell Si@SiO₂@PS/PVDF composites exhibit the lowest tanδ and the highest E_b among the three composites because the organic PS interlayer enhances the interfacial compatibility and promotes the fillers’ homogeneous dispersion in PVDF. The improvement in dielectric properties of Si@SiO₂/PVDF and Si@SiO₂@PS/PVDF composites can be ascribed to the facts that the insulating SiO₂ and SiO₂@PS shells effectively prevent the semi-conducting Si particles from direct contacting, thereby remarkably reducing the tanδ. The enhanced phase interfacial compatibility between the Si@SiO₂ or Si@SiO₂@PS and PVDF matrix reduces the interface defects and suppresses the local electrical field distortion, thereby improving E_b of the core-shell structured Si/PVDF composites. The prepared Si@SiO₂@PS/PVDF composites with a high dielectric constant of 48 and tanδ of 0.07, E_b of 6 kV/mm, have potential applications in the field of microelectronic devices and power equipment.