Higher Order Effects in the Dielectric Constant of Percolative   Metal-Insulator Systems above the Critical Point
  The dielectric constant of a conductor-insulator mixture shows a pronounced maximum above the critical volume concentration. Further experimental evidence is presented as well as a theoretical consideration based on a phenomenological equation. Explicit expressions are given for the position of the maximum in terms of scaling parameters and the (complex) conductances of the conductor and insulator. In order to fit some of the data, a volume fraction dependent expression for the conductivity of the more highly conductive component is introduced. 
W.D. Heiss, D.S. McLachlan and C. Chiteme