Ultrahigh dielectric loss of epsilon-negative copper granular composites

Loss materials have great potential applications in electromagnetic wave absorption and attenuation. In this paper, we report an epsilon-negative composite that has very high dielectric loss (tan δ~100@10 MHz). This percolative polymer composite is filled with spherical micron-sized copper particles. Below the percolation threshold, conductivity spectra showed obvious frequency dispersion and conformed to the Jonscher's power law, indicating hopping conduction. When composites reached up to percolated state, the conduction mechanism changed to electron-like conduction. It is suggested that the electron transfer between copper particles leads to a very high loss of the composites.