Restrained dielectric loss and elevated breakdown strength in Si/PVDF composites by engineering SiO2 shell as an interlayer

As the electronic industry develops rapidly, nowadays, flexible dielectric materials with excellent integrated dielectric performances including high dielectric permittivity (e) and breakdown strength (E-b) but low loss, are highly pursued. In this work, to concurrently improve the e and E-b but restrain the loss of original Si/polyvinylidene fluoride (PVDF) composites, the core@shell structured Si@SiO2 particles first were produced via high temperature oxidation process, and then incorporated into the PVDF to generate morphology-dependent composites with high-e and E-b but low loss. The dielectric properties of the composites were investigated in terms of the filler types and concentrations, frequency, and theoretically fitted using the Havriliak-Negami equation to reveal the SiO2 shell' role in affecting the polarization mechanism. When compared to pure Si/PVDF at high filler loadings, remarkably inhibited dielectric loss and conductivity as well as enhanced E-b concurrently can be achieved in the Si@SiO2/PVDF composites still harvesting a high-e. This is because the insulating SiO2 shell not only effectively prevents the raw Si particles from direct physical contact, but also greatly impedes the long-range charge carrier migration via raising energy barrier subsequently leading to obviously enhanced E-b. Moreover, the dielectric loss and conductivity apparently decrease with increasing the SiO2 shell thickness due to its pronounced suppression effect. The prepared Si@SiO2/PVDF with a high E-b and e but low loss, show bright future uses in micro-electronic devices used for high-voltage purposes.