Low frequency AC conduction and dielectric relaxation in PVDF films

The ac conductivity and dielectric relaxation behavior of uniaxially stretched polyvinylidene fluoride (PVDF) films (~25 μm 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, σ(ω)=Aω^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 ~0.18 eV confirms the existence of dipolar relaxation around 260 K and is identified as the β-relaxation