High dielectric permittivity of percolative composites based on onion-like carbon

The broadband dielectric properties of the onion-like carbon (OLC) and polyurethane based composites of different compositions are presented for the frequency range of 20 Hz–3 GHz and 250–450 K temperatures. It is shown that an abrupt increase in the complex dielectric permittivity at the volume fraction of OLC 10% is associated with the onset of percolation. The revealed critical exponent and percolation point reasonably agree with theoretically predicted values. Composites with 10% of OLC exhibit dielectric permittivity as high as 2000 and conductivity as high as 0.01 S/m at 100 Hz.