How can I derive ionic conductivity value from measured impedance spectra? I am trying to calibrate our new EIS equipment and better understand what I will be measuring. I am taking impedance measurements at room temperature on NaCl solution. Ideally, I need either a diffusion coefficient of an ionic conductivity value. My Nquist plot has a straight line of roughtly 86deg from positive x axis, so it's not quite a Warburg element. Can I treat it as a CPE and still solve for a diffusion coefficient the same way as the warburg coefficient or is there another way to approach it? Thanks
To get to conductivity, I recommend having electrode pairs of known geometric area spaced at a known distance (e.g. parallel plates) or have an electrode pair with a known cell constant for your setup. Then, you can take the high frequency resistance assuming you have accounted for any inductance from leads, etc and use it in the formula: (Ionic conductivity) = (electrode distance)/(resistance*electrode area).
Great, thanks for the suggestion on that. Do you happen to have a reference or name for the ionic conductivity equation you mentioned? I hadn't come across that yet, it looks like exactly what I was looking for.
Also, for the resistance is that the impedance value or something more specific?
Thanks again for the help!
I propose a four-electrode mode cell, e.g. a Z4el[1] using the EIS[2] technique, that is a good tool for your complex[3] task.
1. Two, Three and Four Electrode Experiments : Four-Electrode Experiments https://www.gamry.com/application-notes/electrodes-cells/two-three-and-four-electrode-experiments/
2. https://www.researchgate.net/post/What_is_the_common_way_to_measure_ionic_conductivity_of_a_liquid_electrolyte_How_shall_be_the_cell_designed
3. Electrode polarization impedance in weak NaCl aqueous solutions http://ieeexplore.ieee.org/document/1542460/
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