Dear Dr. Ramaswamy:

In the low frequency domain, the spike can be ascriged to the "diffusion" of anionic species to electrodes. The presence of a spike well defined suggest that diagram be of Nyquist type intead Cole-Cole. This phenomenon seems well supported, in this area. In this sense, it is necessary a software to adjust data, according further physico-chemical model. Seems really,  that after spike, the first semicircle occurs. At end, seems that a third semicircle emerges. A priori, all three phenomena should exihibt an intrinsic relaxation phenomenon, with characteristics relaxation-time each time more short.  Would be interesting the data representation in the form of Bode diagram  log( Z module) versus log(angular frequency). Such aspect support the idea that charge carrier exhibits different types of mobility at medium that depending on a gross-manner of the relation carrier mass/liquid charge.  it is important to determine, the angle between spike and abscissa-axis, this value is meaningful  of physico-chemical interpretation.

Please, consider inner search for RG data-base, it is possible find a great number of impedance question/answer, perhaps one with close similarity to date attached. Oh yes, in the RG there is in toolbar the item search, select proper macro-key, digite proper key-word, and ok.

Kind regards

Marcos Nobre

The EIS result should be analyzed not only with the Nyquist plot, but with the Bode plot (phase, and impedance magnitude vs frequency). I recommend the last frequency as 0.01 or at least 0.1 Hz in order to see the interface response. EIS frequency range for metals is from 50kHz to 0.01Hz and for coating or polymers from 100kHz to 0.01Hz. Please revie the book of doctor Ross Macdonald.

Dear Dr. Ramaswamy:

Also:

The spike and abscissa-axis should have a angle different of 45o. Such aspect is further supported by blocking-electrodes (to specific carriers), as stainless steel is to anionic kind of carriers. In this sense, the spike would be represented by an equivalent circuit electric type RC serie, resistance and capacitance in serie. It is possible, that close to electrodes be formed from ionized carriers, some kind of double-layer, with diffuse-layer characteristic. In this sense, during modeling the capacitive behaviour expected is non-ideal, leading to use of concept of dispersive capacitance, one to each semicircle. See, typically, two semicircle can be only resolved when relaxation frequency differs of three magnitude orders, for two or lower one semicircle exhibits some part superimposed.

Kind regards

Marcos Nobre

Dear  Mr. Marcos,

Tks for ur valuable suggestions. In polymer electrolytes both anions and cations take part in conduction. Cations being small in size their mobility will be some what high when compared to anions. Is there any relation between the observed semicircles and relaxation of both the ions. does each semicircle represents the relaxation for anion and cation. Plz clarify

Hai

 You should select  the frequency range mHz to MHz. At that time you should conform the  formation of second semicircle or warburg line (low frequency region). After that we will discussed about the anion and cation diffusion. Again  you will do the repeat the measurement.

Dear Dr. Ramaswany:

See, impedance spectroscopy is a non-trivial characterization technique; in this sense EIS also is a complex characterization technique.

There are a great number of variables that can turn the interpretation simpler or more complex. The question proposed provides some information but the data set presented is not complete. In this sense, supposing aqueous electrolyte, the impedance of the interface and a metal electrode at which no charge transfer processes occur (blocking contacts) as mentioned should obey, see capacitance effects and the constant phase angle over a wide frequency range, in the which the exponent n is typically in the range of 0.7 to slight below of unity. In this sense, each one of three relaxation phenomenon identified contains in tis physical interpretation a non-ideal capacitance. Due the blocking nature of electrode used only the first would be assigned to accumulation of mobile kind of carriers. Such, response should be more simple that Warburg’s impedance behavior since the observation of this kind of phenomenon is correlated to electrodes semi-permeable to some kind of carrier. Another two semicircles cannot be assigned directly to ionic kind carrier present in the medium. In fact, such species cannot be “seeing” directly in impedance spectrum, only in the form of the double layer. See, as a whole, a set of steps is necessary to assignment of each part of response. The presence of spike in a blocking electrode is the key, since another semicircle would be assigned to double layers, while the third semicircle at highest frequency domain would be assigned to the bulk phenomenon.

Kind regards

Marcos Nobre

Dear Dr. Ramaswamy:

First of all, you have 2-phase system with fractal structure. It could be modeled by Foight model. Than you have to determine the structure of your channel of charge transfer. Further, on analyzing Bode plots you’ll obtain needed peculiarities on conductive properties of your electrolyre.

Dear Dr. Ramaswamy:

try, also, to measure the electrolyte , if possible, without the polymer.