Significantly reduced dielectric loss and conductivity in polymer-based nano-composites from a suppressed interface Coulomb force

A Coulomb force at an interface, namely induced polarization, has been found to have a significant effect on the permittivity of 0-3 type polymer-based composites with Si-based semiconductor fillers. These composites have the disadvantage of a higher dielectric loss and conductivity but the advantage of a larger permittivity when compared to composites filled with surface modified Si-based semiconductors. In the present work, the dielectric and conductive properties of 0-3 type varied polymer-based composite systems containing α -SiC and SiO₂@SiC nanoparticles, respectively, were investigated in detail. It was found that use of a SiO₂@SiC filler instead of neat SiC could effectively decrease the Coulomb force between the SiC and polymer, the overall induced dipole moment, the real permittivity of SiC and thus the measured permittivity of the composite. As a result, significantly decreased dielectric loss and conductivity as well as elevated breakdown strength were obtained thanks to the reduced Coulomb force at the interface. The lowest loss and conductivity achieved were 0.03 and 6.05  ×  10⁻⁷ S cm⁻¹, respectively, at 100 Hz for 20 vol% SiO₂@SiC-filled polyvinyl chloride (PVC)-based composite. Moreover, the dependence of interface-induced polarization on polymer polarity in three SiO₂@SiC-loaded polymer-based composite systems was investigated and the lower polarity of polymer could favor the decline of induced polarity in the SiC. This work might lead to an easy way to obtain promising composite dielectric materials by suppressing the interface Coulomb force. (paper)