AC conductivity and dielectric relaxation behavior of solution grown poly (vinylidene fluoride) films

Ac conductivity [sigma(m)(omega)], dielectric constant [epsilon'(omega)] and dielectric loss [epsilon ''(omega)] of solution grown poly(vinylidene fluoride) (PVDF) films (thick similar to 85-100 mu m) 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 sigma(omega) = A omega(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 similar to 1.1 x 10(18) - 4.8 x 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 alpha(c)-, the alpha(a)- and the beta-relaxations, appearing from high temperature side to the low temperature side in the dielectric loss versus temperature spectrum, having activation energy similar to 0.232-0.474 eV, similar to 0.189-0.226 eV and similar to 0.052-0.068 eV, respectively have been observed in the present investigation. The activation energies (similar to 0.02-0.05 eV) of the charge carries calculated at 77 K indicates the evidence of electronic hopping conduction in the low temperature region.