Study of dielectric relaxation in polymer electrolytes

An attempt has been made to study the relaxation characteristics of PVA-H3PO4 and PVA-H2SO4 complex electrolytes in the form of thin films. Various dielectric parameters such as dielectric constant (epsilon'), dielectric loss (epsilon ") and loss tangent (tan delta) have been determined in the temperature range 20-160 degrees C at different frequencies and molar ratios. Using Cole-Cole plots (epsilon " vs epsilon'), the values of epsilon(s) (static dielectric constant), epsilon(infinity) (infinitely large frequency dielectric constant) and relaxation times have been calculated at room temperature. Relaxation time is determined from the variation of loss tangent with temperature at different frequencies. It is observed that relaxation characteristics show Arrhenius type behaviour and there is a decrease in activation energy with an increase in acid concentration for various complexes. The study of dielectric relaxation as a function of temperature at constant frequency shows two types of relaxation processes which are interpreted in terms of dipole-segmental motion (alpha-relaxation) and side chain dipole group motion (beta-relaxation). (C) 1998 Elsevier Science Ltd. All rights reserved.