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

• Published in: Journal of applied polymer science 2008-05, Vol.108 (4), p.2540-2549
• Main Author: Hanafy, T.A
• Format: Article
• Language: English
• Subjects: Applied sciences; charge transfer; dielectric properties; Electrical, magnetic and optical properties; Exact sciences and technology; metal-polymer complexes; Organic polymers; Physicochemistry of polymers; Properties and characterization
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.27567

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 10⁶ Hz, respectively. Three relaxation processes--αa, αc, and ρ--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 αa and αc 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 ρ-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 (306-333 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.