Dear Dr. S. S. Danewalia ,

in my experience using the EIS technique, inductive loops at low frequencies could be generated by the presence of adsorbed reactive phases (e.g. metallic ions) on the surface, probably correlated also to a diffusive process.

Best regards, Pierluigi Traverso

I've seen some EIS plots loop "backwards", when I worked with oxygen conductors. This typically happened, when I was doing multiple measurements at various temperatures, and I attributed this to sample still heating up in mid-measurement (and changing in conductivity). Try letting it equilibrate for longer and then repeat the measurement. If this loop is still there, then it's a different issue. But at least you can rule out transient effects.

Dear Sir,

Thank you for your prompt reply.

1. Is the loop given in this figure an 'inductive loop' (with negative imaginary impedance)?

2. Do the metallic particles FROM THE SAMPLE adsorb at the surface, or it is diffusion of Platinum coating particles into the sample at higher temperatures?

Kindly give your expert opinion.

Best regards,

Satwinder.

Dear Dr. S. S. Danewalia,

first of all I apologize for the delay in my reply. What I have previously suggested to you is the result of my experience but must then be correlated to both the sample studied and the experimental conditions used. In particular, to formulate specific hypotheses I should know in detail how the sample is made, what is the solution in which the measurement was made, how many times this phenomenon happens, etc. Personally I have no experience of EIS measurements conducted at such a high temperature but, if you have the possibility, I would try to do a chemical and morphological analysis of the sample surface, before and after the EIS measurement.

My best regards, Pierluigi Traverso

@Pavel Mardilovich

Dear Sir,

Thanks for your reply. That is really a good point to consider. I will check the same for my very next measurements.

Regards,

Satwinder.

@Pierluigi Traverso

Dear Sir,

Its your kindness that you are responding and its never late when we are discussing science.

These samples were not measured in solution form. Rather, as mentioned in the description, we measured the impedance of solid pellets coated with platinum both the sides. The diameter of the pellet ranges upto 20cm with thickness around 2-3 mm. Samples are mount in the probostat using a spring loaded system. Measurements are taken over wide frequency as well as temperature range. The platinum deposited on the surface may have chances to diffuse into the pellets at higher temperatures. That information might help you further thinking what's happening.

Regards, Satwinder.

Dear S. S. Danewalia,

in short, some tiny parts of the platinum metal electrode, deposited on the surface, start to diffuse, at least, into the Pt//pellets' electrode(s); in more details:

1) Pt diffuse into the interface[1] , at high temperatures; this results, usually, as a transient effect, that is very sensitive to VDC polarization[2]. Remeasure, please, more EIS(s), using a list of VDC polarization values; keep, all other parameters, the same.

2) in addition, if Pt particles are able to diffuse, deeper into the pellet, or a "similar" scenario[3], you will, certainly, note supplementary (and permanent) changes in the other part of your EIS spectrum; this (internal) Pt will modify the full (and high Freq.) EIS spectra, e.g. a (full band, "signature") effect, set in stone.

Also, could you, please, say(?), what is your (glass-ceramic) pellet[3] ?

1. This seems in such a poor bibliography as a, more, clear and popular, turnabout, case (Z.imag. "always", inductive) , but NOT the only one, case: "I found some reports where it is said to be "inductive" ONLY IF imaginary impedance becomes positive. In my case, imaginary impedance remains negative all the times."

Zimag. can pass to other ("floating" positive modes) values[4], if it's T (time constant) is very "near" other (capacitive etc.) co-existing phenomena ("float" modes). Also, a thermally, only, driven "absorption//desorption" chemical potential "u", of the charged particles (carrier) results into EIS (low Freq.) "noise", mainly, on the Z.real axis. For un-charged particles, it results into EIS (low Freq.) "noise", on both (the Z.real and Z.imag.) axes, at VDC=0V; a composition-based variations in chemical potential "u", Z= (V + U) / i. : U= u / (n*e).

This is why we have a poor (annotated) bibliography on these "noisy", but sometimes, "inductive" Z-effects, as your good Z-effects.

So, the (EIS-background) thermal "noise" u-effects into EIS can be, practically, "reduced", if add a directional force, say, by adding a VDC polarization value[2]; we increase the EIS "signal to noise" ratio.

2. So, could you, please, say, what is your VDC polarization value[4] ?

3. A similar ("negative" diffusion) scenario is, also, possible, depending on the synthesis and the morphology of your (glass-ceramic) pellets[4].

4. https://www.researchgate.net/post/What_are_the_possible_explanations_of_the_inductive_loop_at_low_frequencies_in_Nyquist_plot_EIS

@ Ioannis Samaras

Dear Sir,

Thanks for your detailed answer. These glass-ceramics are silicates majorly (45 mol%) with alkali and alkaline earth metal oxides (Na2O, CaO; 40 mol%) as modifiers. Additionally samples contained (~15mol%) of transition metal oxides such as TiO2, ZnO etc. dc voltage was presently kept at 0V. We will try to get it measured at list of Vdc values, as per your suggestion.

Two different phase is available in the sample medium. It leads to inductive effect .jwL- part in your impedance (L,C,R)

Dhananjeyan Manikka

Dear Sir,

First of all thanks for your reply.

Can you please suggest couple of references to support this fact, so that I can dig further to understand the phenomenon?

Hello,

It would be nice to know the start and stop frequencies used for the test. The real and imaginary values are quite large so I am guessing a low frequency test.

You write 'Glass-ceramic pellet was coated both sides with Platinum' which sounds like a description of a ceramic capacitor, except the ones that I purchase are rectangular and melt at 600C.

Temperature is always suspect when testing ceramic devices at room temperature. Your temperature is much higher.

Regards,

Tim

Dear @Tim Orr

You guessed it right; these would form ceramic capacitor.

Frequency range was 1 Hz - 10 MHz.

Regards,

Sarwinder.

Any book on impedance spectroscopy dealing about electro-chemical reactions. Hand book of batteries by David Linden

Dear Sir, from point of view of corrosionist, low frequency inductive loop is explaining by adsorption of some kind of species in local places at the surface. I found this kind of phenomena during pitting corrosion (local corrosion and anodic dissolution, metal ions species formation) or for metallic electrode with deposited polymeric coating with local delamination (blister under paint corrosion). (At the frequencies lower than 1- 0.1 Hz). So I suppose that in your cases some local phenomenon at the electrode surface are taking place. Best regards.

Yes, a "corrosionist", frequently, observe, low frequency inductive loops (LFiL) "at the frequencies lower than 1- 0.1 Hz".

However, it is possible to observe[1] such LFiL, starting at much higher (~10Hz)[2] frequencies, also.

1. Exploring single electrode reactions in polymer electrolyte fuel cells https://www.sciencedirect.com/science/article/pii/S0013468606008243

2. At Room Temperature (273+25)K

@ A. Nazarov

Dear Sir,

I am thankful for your response. I also read about low frequency inductive loops. In present case, the loops were formed at quite high frequencies.

Low frequency inductive loops (LFiL) push on at relatively "quite high frequencies" (dear S.S.Danewalia), but at a strikingly High(er)[1] Temperature (HT). HT, beyond any doubt, favors activation[2] of more (RT-immobile) mobile particles.

1. At a noticeably "high" Temperature (273+600)K.

2. Thermally driven "absorption//desorption" effects in chemical potential "u", activate the mobile particles. It results into EIS (low Freq.) "noise" due to the kinetics of the "heavier" particles; heavier than electronic carrier, variations in Z at quite high frequencies; So, LFiL is a composition-based variation in Z, due to chemical potential "u" (thermal) variations, Z= (V + U) / i. : U= u / (n*e).

if the phenomenon is difficult to understand, try to check your instrumentation. Did your instrumentation follows the requirement for impedance measurement good enough?

See this paper, hopefully it can help if there is some problem related to your instrumentation:

http://jes.ecsdl.org/content/162/1/H47.full

@Marlin Ramadhan Baidillah

Dear Sir,

Thanks for responding and sharing that article.. It's really helpful!