Dielectric dispersion and ac conductivity in-Iron particles loaded-polymer composites

Polymer composites of an epoxy resin matrix with randomly dispersed Iron micro-particles in various amounts were prepared and their dielectric spectra were measured in the frequency range 5 Hz-13 MHz and temperature interval from ambient to 140 degreesC. Obtained data were analysed by means of electric modulus formalism. Interfacial or Maxwell-Wagner-Sillars relaxation process was revealed in the frequency range and temperature interval of the measurements, which was found to follow the Cole-Davidson approach for the distribution of relaxation times. The examined systems exhibit strong dispersion with frequency. At low frequencies ac conductivity tends to be constant, while at higher becomes frequency dependent varying as a power of frequency. Conductivity increases with temperature in the low frequency regime, remaining almost unaffected at higher frequencies. (C) 2003 Elsevier Ltd. All rights reserved.