AC Conductivity and Dielectric Relaxation Behavior of Solution Grown Poly (Vinylidene Fluoride) Films

Abstract

Ac conductivity [σ m (ω)], dielectric constant [ϵ′(ω)] and dielectric loss [ϵ”(ω)] of solution grown poly (vinylidene fluoride) (PVDF) films (thick ∼85–100 μm) have been measured in the temperature range 77–400 K and in the frequency range 100 HZ–10 MHz. A frequency dependent conductivity described by the relation σ(ω) = Aω s , is observed in the low temperature region where s < 1 and is independent of temperature up to 200 K and decreases with increase in temperature. The density of states at the Fermi level [N (E F )] estimated at 77 K and 100 kHz is ∼1.1 × 10 18 − 4.8 × 10 19 cm−3 eV−1. The dielectric constant in the low temperature region (< 200 K) shows a very weak frequency and temperature dependence. However, in the higher temperature region (> 250 K) a strong frequency dispersion of dielectric constant and strong temperature dependence of ac conductivity are observed. Three relaxations; the α c − , the α a − and the β-relaxations, appearing from high temperature side to the low temperature side in the dielectric loss versus temperature spectrum, having activation energy ∼0.232–0.474 eV, ∼0.189–0.226 eV and ∼ 0.052–0.068 eV, respectively have been observed in the present investigation. The activation energies (∼0.02–0.05 eV) of the charge carriers calculated at 77 K indicates the evidence of electronic hopping conduction in the low temperature region.