For my sample, I calculate the temperature dependence of relaxation frequency for Impedance and Modulus imaginary function. I obtained negative slope. What will be the reason if the slope of the Arrhenius plot activation energy value is in negative?
Dear Cyril,
The slope of the Arrhenius plot is very often negative, because of the way you are doing the plot. However, if you pay attention to the equation that you are plotting, probably you will discover that indeed the negative sign is included. This means that the activation energy that you are getting from the Arrhenius slope will be positive.
This is the case for instance when you ar measuring with a DMA as a function of emperature for different frequencies.
Please look carefully your data and the used equation.
Kind regrads,
Prof. J. San Juan
Is it wrong in my calculation that the slope is in negative? is there any meaning for the same?
Dear Cyril,
I think that you data could be good. The slope is negative because it must be negative according the equations.
Probably you are measuring relaxation peaks as a function of temperature at different frequencies, or as a function of frequency at different isothermal temperatures. Both measurements will give similar results.
I send you here attached a paper from a summer school in 2001 (you can also download it from my profile) in which this is theoretically described. In particular the equation (1.2.59) give you the plot of Ln(f) as a function of 1/T and as you can see, the slope of this plot has a negative sign. This means that your plot should be correct an the slope is negative, but the activation energies are obviously positives.
I hope this could be useful for future works.
Kind regards,
Prof. J. San juan
Thank you sir for the explanation. I am learning carefully about the Impedance spectroscopy. It is an ocean..
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