Charge Carrier Transport in Composites Based on Polyethylene and Copper-Containing Fillers

The paper presents the study of two types of composite materials containing copper micro- and nanoparticles in a polyethylene matrix. Two types of copper-containing fillers were used to prepare the composites: microparticles with an average size of 3.5 μm; nanoparticles of an average size of 13 nm with a core-shell structure. The study of the temperature dependence of the electrical conductivity of copper microparticles at fixed pressures showed that the shell formed on their surface, consisting of copper oxide, exhibits a semiconducting character. Additionally, the conductivity and static permittivity of polyethylene infused with copper nano- and microparticles were examined near the percolation threshold. Discrepancies emerged between experimental findings and predictions of the modern inhomogeneous systems theory at conductivity levels below a certain threshold. In the composites with copper nanoparticles located below the percolation threshold, an additional influence on both electrical conductivity and permittivity was observed. The reasons for this effect are discussed here simultaneously taking into account the spatial structure of the hierarchical model for composite materials proposed by the scientific group of I. Balberg.