Low frequency AC conduction and dielectric relaxation in PVDF films

Abstract

The ac conductivity and dielectric relaxation behavior of uniaxially stretched polyvinylidene fluoride (PVDF) films (/spl sim/25 /spl mu/m thick) has been measured in the temperature range 77-400 K and in the frequency range 100 Hz-10 MHz. In the low temperature region up to 100 K, the measured ac conductivity is nearly independent of temperature and shows strong frequency dependence which could be well described by the relation, /spl sigma/(/spl omega/)=A/spl omega//sup s/, where the exponent 's' has been found close to unity. At temperatures above 200 K, the ac conductivity shows a strong temperature dependence. The measured dielectric constant in this temperature region shows a frequency dispersion. The activation energy of the relaxation calculated by Fuoss approach is /spl sim/0.18 eV confirms the existence of dipolar relaxation around 260 K and is identified as the /spl beta/-relaxation.