I measured resistance of my solid electrolyte with Au as blocking electrode. Real impedance value did not start from zero value, rather higher than zero value. Should I subtract that value of real part from total resistance? I have shown my different considerations about data in attached file. Which one is right?
I am delighted very much with last answer by Kamran Rasool.
In the first slide, the resistance which you have denoted by Rb is your series resistance. You should not subtract this value. Instead, you have to consider this value as your series resistance.
Dear kavita Thanks a lot for your quick response.Will you please explain that what is meant by series resistance.Is it different from grain bulk resistance??
The intercept between the semicircles and X-axis is resistance. To do so, you should fit your spectrum with proper circuits.
Seek Solid states papers by Ukshe E.A.and Bukun N.G. in Russian Electrochemistry.
First of all non-ideal (Depressed semicircle) or deviation from Debye behavior and origin of different relaxations can be due to Grain orientation, Grain boundary, Sub-grain boundary, Electrode effect and also be due to Interface functional groups. Usually multiple relaxations can be associated with polycrystalline structure too.
You can observe these multiple relaxation from Cole-Cole plot, but some times this plot can't give you sufficient information. Then you can try Modulus plane plot or comparison between imaginary parts of M'' and Z''.
In your case, in my opinion three relaxation is dominant.
one is electrode/interface effect (Lower frequency), second is grain boundary (Intermediate frequency) and third one is bulk or grain(higher frequency).
Values of resistance can be calculated directly from Impedance data or you can fit these curves with some software or do simulation .
I hope my answer will serve your purpose.
Further you can look at these research papers, hope these papers will be helpful for you.
1) http://apl.aip.org/resource/1/applab/v101/i2/p023114_s1?isAuthorized=no
2) http://apl.aip.org/resource/1/applab/v101/i25/p253104_s1?isAuthorized=no
Cheers!
Dear sir Kamran,You mentioned three relaxations in my data.I want to ask That Should I subtract the value of real part(Z') before higher frequency(1MHz) because semicircle starts with frequency 1MHz at value 4471(ohms).Is it a value for bulk resistance (as I mentioned in slide 1) or the value of bulk resistance is that which i mentioned in slide 2??
@Kamran rasool,Is it(4471 ohms) the value of series resistance as mentioned by kavita and the values for grain boundary and bulk resistances are as I shown in slide 2??Please clear this point.Thank you so much.
Dear Mahreen!
i can't understand your question properly.
but you shouldn't subtract value of real part of impedance.
And this is not so simple to say that at IMHz resistance corresponds to your bulk.
Try to perform fitting of your experimental data for actual finding. Because with multiple relaxation this is not easy to distinguish electroactive regions.
Actually the value of capacitance and resistance both, obtained from fitting actually gives us clue about the different electroactive regions. e.g. value of capacitance for bulk or grain( ~10^-12F) , Grain boundary (~10^-12F,10^-11F,10^-10F) and electrode or interface effect should be (~10^-10F,10^-9F,10^-8F).
Regards
I mean, that ii measured conductivity of the grain true, if measured capacity at maximal frequency being inside 10^-10F. It is true ?
Sir Elkin,By fitting my data using Zview software I got bulk capacitance of the order of 10^-9F and grain boundary capacitance of the order of 10^-6F.
Dear, Mahreen!
I think you haven't use proper circuit for fitting. i Think these values are not correct.
Try some other circuit.
Please look at this paper
Methods to study the ionic conductivity of polymeric electrolytes using a.c. impedance spectroscopy, Xinming Qian á Ningyu Gu á Zhiliang Cheng, Xiurong Yang á Erkang Wang á Shaojun Dong, J Solid State Electrochem (2001) 6: 8±15
DOI 10.1007/s100080000190
Hi, i am trying to do some EIS studies for my ceramic coating but the nyquist plot i get at the high frequency region i.e at the beginning of the plot is more like a hook shaped rather than a semi circle. Can anybody tell what may be the cause of getting this kind of plot.
Slid two best describes your results. your fitting results actually can decide that if Rb is a contribution from grain or multiple phases (for example mixture of grain+grain boundry+ multiple phase interface etc) depending upon the capacitance (as mentioned by Kamaran). if you don't have the fitting software you can roughly estimate the mixed resistance, considering Rb only (subtracting series resistance). I suggest you to conduct another measurement as your series resistance is too high 4.5 kohm.
As most of the experts suggested, slide 2 is correct way of calculating the resistance.
THe initial resistance is cell or (solution) resistance which should not incude with your material's impedance. But it must be accounted for the purpose of fitting the EIS plot through suitable softwares. The total impedace of the plot would be taken from the contribution of grain (1st semi circle) and grain boundary (2nd circle) Rb+Rgb without including the initial cell resistance (pure real resistance).
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