Dielectric relaxation and alternating-current conductivity of gadolinium-doped poly(vinyl alcohol)

The dielectric constant, dielectric loss factor, and alternating-current conductivity of Gd-doped poly(vinyl alcohol) (PVA) samples have been studied in the temperature and frequency ranges of 290-450 K and 50-5 x 10(6) Hz, respectively. Three relaxation processes-alpha(a), alpha(c), and p-have been obtained. The first one is due to the rotation of OH and C=O groups inside the amorphous part of PVA. The second process is due to the dipole relaxation in the crystalline phase of the sample. The changes in the peak position and height of a, and a, have been interpreted in light of the formation of complexes between GdCl3 and OH and C=O groups of the PVA structure. On the other hand, the p-relaxation process is due to the space-charge formation between the different phases inside the PVA samples. Alternating-current conductivity measurements of the investigated samples have revealed that the hopping conduction mechanism is predominant. The maximum barrier height and the activation energy have been calculated and reported. In the low temperature range (306333 K), the responsible conduction mechanisms of PVA doped with 2 or 4 wt % GdCl3 have been found to be small polaron tunneling and quantum mechanical tunneling, respectively. (C) 2008 Wiley Periodicals, Inc.