Please suggest me what kind of behaviour happen here, when ac conductivity decreases with increasing frequency. Attached figure shows. Suggest me what type of conduction processes are involved here.
Dear Artur Braun,
No Inductivity. Variation of ac conductivity with the frequency.
In order to answer your question, it is worth noting the following:
The conductivity value (s) of an electrode is a bulk parameter
Of the electrode. One can determine the conductivity value (s) under AC condition
By the following equation:
Z= (rL/A) = (L/sA) =R ( Eq.1)
Where
Z is the AC impedance of the electrode, can be determined by plotting Z versus Log[ angular velocity in term of frequency(w)], From Bode plot. Also, Z is an interfacial parameter, not bulk parameter of the electrode.
r is the resistivity of the electrode, a bulk parameter of the electrode.
A is the surface area of the electrode.
L is the length of the electrode.
s is the conductivity of the electrode, a bulk parameter of the electrode.
R is the resistance of the electrode.Also, Z is an interfacial parameter, not bulk parameter of the electrode.
Z would be equal to R from (Eq.1), when  the angular velocity (w)=1,
Where
w = 2(Pai)f
(Pai)=3.14
f is the frequency, which is equal to 0.16 Hz in bode plot (Z Versus log w) at this situation.
So, since, f=o.16 Hz, w=1, log (w), and therefore, log (1) =0.
At this situation the vector parameter Z becomes , equal to the scalar parameter R, and
s can be determined as the inverse proportionality constant (invariant) between R and L, Eq.1.
So, to answer your question, the s value should remain nearly constant, as it appears in the plot, till
a certain value of the frequency(f), in which s starts to decrease.
Can you tell me what was the f value in which s starts to decrease.
Dear Moumin
At a frequency (f) of 100000 Hz or higher, the AC conductivity become a DC conductivity , it could be the heat which causes the decrease of the conductivity, or increase of the resistivity, dependent on the materials of the tested sample.
Dear Moumin
The plot of log (Sac) versus Frequency,
Where Sac is the ac conductivity,
normally starts with high frequency, 106 Hz, and ends with low frequency,10-2 Hz. Therefore, you plot indicates that as the frequency decreases, the corresponding ac conductivity increases till the frequency 105 Hz, in which the ac conductivity attained nearly constant value.
All the basic passive linear elements (i.e. resistance, inductive reactance, and capacitive reactance) are dependent on the frequency. The resistances and inductive reactances increases with the increase in the frequency while the capacitive reactances decrease with the increase in the frequency; however, the shown change in the conductivity seems to follow the characteristics of a non-linear element of system. Probably, the shown figure is associated with a dielectric. Anyway, there are numerous conditions that affects the conductivity of materials. For example: http://dx.doi.org/10.4236/ns.2011.312129
From where did you get that response?!
What would be the cause if ac conductivity initially increases with frequency and then become stable ?
This is due to a fact at high frequency the capacitive reactance of the sample decreases, hence the impedance is reduced, which causes an increase in the ac conductivity of the sample.
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