Recognition of a new permittivity function for glycerol by the use of the eigen-coordinates method

Abstract

Measurements of real and imaginary parts of the relative complex permittivity of glycerol were carried out in the frequency range 1 mHz-1 MHz at different temperatures between 188 and 263 K. The permittivity data have been analyzed thoroughly by a new data curve-fitting approach that involves the so-called eigen-coordinates method in conjunction with a separation procedure and the inverse permittivity formulas. A new single permittivity function, based on the so-called recap element picture for a self-similar (fractal) structure, has been recognized to describe well such data over the entire frequency range studied. The recognized dielectric function enabled us to infer an electrical equivalent-circuit network for the glycerol sample studied that involves a series combination of two recap elements, reflecting the existence of two different dielectric relaxation processes in glycerol. The temperature dependence of the relaxation times τ1(T) and τ2(T) entering into the identified permittivity function was found to obey nearly an Arrhenius behaviour with activation energies E1 ≈ 114 kJ/mol and E2 ≈ 94 kJ/mol. The recognized permittivity function can be justified by presuming that the processes represented by the recap elements characterized by the parameters (ν1, τ1, E1) and (ν2, τ2, E2) are linked to 'donor-like' and 'acceptor-like' charges formed from the infinite hydroxyl hydrogen bonds. © 2002 Elsevier Science B.V. All rights reserved