Application of an alternative representation to identify models to fit impedance spectra

The aim of this work is to improve a new alternative representation of impedance data proposed in a previous communication that greatly facilitates identification of the number of contributing elements and to use this approach to provide starting parameters for non-linear least squares fitting. This alternative representation allows estimation of the number of processes involved in the impedance spectra with a greater degree of confidence and to discriminate overlapped processes within a factor of 3 in their relaxation frequencies for processes with similar strength, using a model constituted by R-CPE elements.The starting parameters for the non-linear fitting can be obtained from the equations proposed for the simplified behaviour of the impedance data. Additionally two types of plots are proposed to get a further rough estimation of the resistance and capacitance values.The approach was tested with a simulated and an experimental case. (c) 2005 Elsevier B.V. All rights reserved.