Abstract:
A sharp increase in the effective dielectric constant of composites with an ethylene vinyl acetate matrix at carbon black concentrations corresponding to the percolation region has been established, as well as the presence of a maximum dielectric loss at concentration, when the dominant contribution to conductivity is due to field emission. A correlation has been revealed between the dependences of the effective dielectric constant and conductivity on the carbon black content. In composites with a carbon black concentration corresponding to the percolation point and higher, a deviation of the experimental dependence of the capacitor capacity on the sample thickness from the calculated one was found. It is shown that the degree of deviation increases with increasing conductivity and decreasing frequency. At a conductivity value greater than $\sim$2 $\Omega$$^{-1}$ m$^{-1}$, the capacitance of the capacitor ceases to depend on the thickness of the sample. An approach based on the quasi-electrostatic approximation is proposed to explain the results obtained, as well as the high values of the effective dielectric constant of semiconducting materials.
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