High dielectric permittivity silver/polyimide composite films with excellent thermal stability

Silver/polyimide composite films were prepared through simple ultrasonic dispersion and subsequent in situ polymerization process. Dependence of dielectric properties of the films on volume fraction of Ag particles, frequency, and temperature was investigated. The percolation threshold of the films was only 0.122, which was lower than the theoretical value (0.16). The effective dielectric permittivity of the film with $12.5\mathrm{vol}\%$ of Ag fillers achieved 400 at ${10}^3\mathrm{Hz}$ . The relative tolerance of dielectric permittivity of the film with $12.0\mathrm{vol}\%$ of Ag fillers in wide temperature range was less than 4.0%, which would satisfy the need in practical applications.