Dielectric investigations and ac conductivity of polyvinyl alcohol films doped with europium and terbium chloride

Differential scanning calorimetry (DSC) was used to identify the phase transitions of polyvinyl alcohol (PVA) doped with europium chloride (EuCl3) and terbium chloride (TbCl3). The dielectric constant and the loss tangent behavior of the investigated samples were studied as a function of temperature in the frequency range 1-100 kHz. The detailed analysis of the results showed that dielectric dispersion consists of both dipolar and interfacial polarization. The temperature coefficient of permittivity (TCP) and the electrical dipole moment (mu) were calculated. Also, the activation energy for the glass relaxation process from the dielectric loss tangent measurements was calculated. Measurements of the ac conductivity as a function of frequency at different temperatures indicated that the correlated barrier hopping (CBH) model is the most suitable mechanism for the ac conduction behavior. The ac parameters, such as hopping distance (R,R-min), polaron binding energy (U-M) and Coulombic barrier height (U-h) were calculated. (c) 2008 Elsevier B.V. All rights reserved.