Electrical percolation and electromagnetic properties of polydimethylsiloxane composites filled with Ag nanoparticles of different sizes

Abstract This paper deals with the electrical properties of polydimethylsiloxane nanocomposites filled with Ag nanoparticles (AgNPs) of different sizes. The measurements were carried out over a very broad range of frequencies (20 Hz‐40 GHz), and the results showed that the percolation threshold in the composites is close to 20 vol% and that it is almost independent of particle size. The observed critical exponents reasonably agree with the theoretical values. Above the percolation threshold, the values of dielectric permittivity and electrical conductivity are quite high, ε′ ≈ 10⁷ and σ ≈ 1 S/cm at room temperature and frequency of 129 Hz (which is close to our low frequency limit). The dielectric permittivity of composites decreases strongly with frequency, especially in the microwave range, while the frequency behavior of conductivity strongly depends on the concentration of nanoparticles. Nevertheless, the electrical conductivity and the dielectric permittivity remain high at microwaves (0.1 S/m and 10, respectively), for composites with AgNPs of size 80 to 100 nm at a concentration of 30 vol%.