Effects of the ionic association-dissociation and adsorption-desorption on the space charge polarization: A new theoretical approach
National Institute of Materials Physics, RO-077125, Magurele, Romania
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Revised: 20 August 2014
Accepted: 9 September 2014
Published online: 28 October 2014
A case where the electrode polarization occurs in dielectric spectroscopy measurements carried out on a liquid crystal cell in which there are paired ions with different transport properties in the presence of generation-recombination processes is discussed. The processes of adsorption/desorption take place at blocking electrode surfaces with different features. The theoretical approach consists in introducing new independent variables with simple significance and in reformulating the fundamental equation for the concentrations of charge carriers and Poisson equation for the electric field. The main purpose of the present mathematical method is to obtain a more convenient analytical expression of admittance and complex permittivity in a form that is easy to use for the interpretation of the experimental data. The expression of the admittance allows suggesting an equivalent electrical circuit according to the processes occurring in the sample volume and at the surface electrodes. The analytical form of the admittance highlights a distinctive term that is proportional to one adimensional parameter which estimates the relative effects of the bulk process in comparison with the interfaces process. Several cases are analyzed and for each an analytical expression is found. In some cases the formulas are available in a simple form.
© Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg, 2014