A.C. Conductivity and Dielectric Properties of Polycarbonate Sheet

Abstract

ABSTRACT The a.c. conductivity σa.c(ω), the dielectric constant ϵ′ and dielectric loss ϵ″ of polycarbonate sheet have been studied in the frequency range 1.5 × 102–5 × 106 Hz and temperature range 294–473 K. A.c. conductivity σa.c(ω) results show that it depends strongly on the frequency and slightly on the temperature, with activation energy between 0.0003 and 0.085 e.V. The a.c. conductivity σa.c(ω) as a function of frequency is well described by a power law AωS where S is the frequency exponent. The obtained values of S < 1 in the first region over the frequency range 1.5 × 102–4 × 103 Hz, the temperature dependence of both a.c. conductivity σa.c(ω) and the parameter S are reasonably well interpreted by the correlated barrier hopping (CBH) model. The second region, where S > 1 over the frequency range 4 × 103–5 × 106 Hz, has a strong dependence on the frequency but near independence of the temperature, suggesting that the conductivity may be interpreted by the Maxwell–Wagner (M–W) dispersion. In the first region, the optical band gap of the material, Eg, and the maximum barrier height, Wm, are calculated, suggesting that there is agreement with that proposed by the theory of hopping of charge carriers over potential barrier as suggested. Spatial inhomogeneity may affect the conduction mechanisms in polycarbonate. The experimental values of dielectric constant, ϵ′ and dielectric loss, ϵ″, show their dependence on temperature and frequency.