New Approach of Data Mining from the Complex Impedance Plane: Parameters You Have Always Wanted to Have

Conventional analysis of data recorded using the Electrochemical Impedance Spectroscopy (EIS) is a relatively simple procedure from the mathematical point of view. It involves an elucidation of electrode processes to derive their characteristic parameters. Another advantage is that it represents a quick visualization tool being still a very sensitive technique [1,2]. However, it has a number of disadvantages too. Often, the interpretation of EIS data using equivalent circuits is quite difficult due to a tedious search for a good fitting correlation. Moreover, results do not give information about number of moving ions (cations or anions), hopping time etc. Knowledge and consideration of these parameters would be very helpful in many electrochemistry-related fields, such as for instance in the development of solid state batteries and in the semiconductor field.

Being unhappy with these drawbacks and limitations of the conventional data analysis method, we recently developed a new approach [4] in which the Z₁ - Z₂ complex impedance plane (where Z₁ and Z₂are the real and imaginary parts of the impedance of materials) has been analyzed, based on Dyre’s random-walk theory. Through this approach we have obtained from EIS data (that are measured anyway), a new set of physical parameters, yet unseen and unmined:

i) the diffusion coefficient D and

ii) the number of moving ions N_ions,

both parameters further distinguishable in the bulk region of the sample as well as at the interface. 

The presentation will explain in detail our recently developed approach that has the potential to find a widespread use in various electrochemical fields, such as in batteries, solar cells, fuel cells and semiconductor industry in general.  The presentation will show, how helpful this approach can be to understand the electrode polarization as well as the ionic transport mechanism in various conductors. In particular, we will discuss in detail recent results achieved on various materials, including selected ionic conductors [3-5], silicons and titanium dioxides [6].

Literature:

1. D. D. Macdonald, Transient Techniques in Electrochemistry, Springer US, 1977.
2. E. Barsoukov, J. R. Macdonald, Impedance Spectroscopy Theory, Experiment, and Application, Second Ed., John Wiley and Sons, New Jersey, 2005
3. S. Stehlik, J. Orava, T. Kohoutek, T. Wagner, M. Frumar, V. Zima, T. Hara, Y. Matsui, K. Ueda, M. Pumera, J. of Solid State Chem. 183 (2010) 144.
4. S. Stehlik, K. Shimakawa, T. Wagner and M. Frumar, J. Phys. D: Appl. Phys. 45 (2012) 205304.
5. D.S. Patik, K. Shimakawa, V. Zima, J. Macak, and T. Wagner, J. Appl. Phys. 113 (2013) 143705.
6. T.Wagner et al., Ms in preparation.