Complex ac conductivity of a carbon black composite as a function of frequency, composition, and temperature

The complex conductivities between 10 mHz and 1 MHz of a series of disorder ed carbon-black-polymer composites have been measured. The carbon black vol ume fractions span the percolation threshold, with de conductivities rangin g from 10(-18) to 10(-6) (Omega cm)(-1). The room temperature results are s imilar to previous measurements on other percolation systems. Conductivity measurements as a function of temperature on a composite sample, slightly a bove the room-temperature percolation threshold, are consistent with the pe rcolation threshold increasing with temperature and becoming equal to the a ctual volume fraction at about 130 degrees C. The real conductivity at diff erent temperatures is shown to scale onto a single curve. An anomalous peak in the real dielectric constant as a function of composition close to the percolation threshold is also observed. [S0163-1829(99)13441-6].