Dielectric properties of films of Ag-ED20 epoxy nanocomposite synthesized in situ. Temperature dependence of direct current conductivity

Abstract

The influence of silver myristate used as a precursor of silver nanoparticles on the direct current conductivity σ dc of epoxy polymer within the concentration range of ≤0.8 wt % was investigated. The value of direct current conductivity was determined on the basis of analysis of the frequency dependence of complex permittivity within the frequency range of 10−2–105 Hz. The temperature dependence of σ dc is composed of two regions. The dependence corresponds to the Vogel-Fulcher-Tammann empirical law σ dc = σ dc0exp{‒DT 0/(T-T 0)} (where T 0 is the Vogel temperature and D is the strength parameter) at temperatures higher than the glass transition temperature T g. At the same time, T 0 does not depend on the concentration of nanoparticles. The Arrhenius temperature dependence characterized by activation energy about 1.2 eV is observed at temperatures lower than T g. The observed shape of the temperature dependence is related to the change in the mechanism of conductivity after “freezing” of ionic mobility at temperatures lower than T g. The value of σ dc is increased as the concentration of nanoparticles is raised within the temperature range of T > T g. The obtained dependence of σ dc on silver myristate concentration is similar to the root one, indicating the absence of percolation within the studied range of concentrations.