Relaxation times/frequencies of Polarization Mechanisms

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Discussion Overview

The discussion revolves around the relaxation times and frequencies of various polarization mechanisms, specifically examining the order in which these mechanisms decrease with frequency: space charge/interface, dipole, ionic, and electronic. Participants explore the theoretical underpinnings and implications of these mechanisms in the context of dielectric properties.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that polarization mechanisms decrease in frequency due to the inertia of the degrees of freedom, with heavier ions moving slower than lighter electrons.
  • One participant notes that the characteristic frequencies for absorption vary, with space charge having a frequency of zero, dipole orientation extending into the microwave range, and ionic and electronic transitions occurring in the IR and UV spectrum.
  • Another participant expresses confusion about the relative frequencies of interface and dipole polarization compared to ionic polarization, questioning why interfacial polarization occurs at the lowest frequency.
  • It is mentioned that interface polarization is largely due to classical currents of charge, described by the Drude formula, which suggests a resonance at zero frequency.
  • Dipole orientation is characterized by rotational motion with resonance poles in the microwave/far IR, while ionic polarization is associated with optical phonons in the IR range.
  • A participant seeks references connecting Drude theory to interface polarization, indicating a gap in their understanding.
  • Another participant states that boundary polarization can be described using macroscopic electrodynamics and suggests that equivalent RC networks can illustrate this effect, with characteristic frequencies being low compared to other mechanisms.

Areas of Agreement / Disagreement

Participants express differing views on the relationships and frequencies of the polarization mechanisms, with some points of clarification offered but no consensus reached on the underlying reasons for the observed order.

Contextual Notes

There are unresolved questions regarding the connections between Drude theory and interface polarization, as well as the specific mechanisms that dictate the frequency order of the different polarization types.

citw
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Why do polarization mechanisms decrease with frequency in the following order:

Space charge/Interface

Dipole

Ionic

Electronic

See page 3 in the attached document for reference.

Edit: corrected error in wording
 

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I would rather say they decrease in that order!
In general the maximal frequency depends on the inertia of the degrees of freedom. It is clear that an ion can't move as fast as an electron as it is heavier.
A more elaborate argument goes like this: The degrees of freedom have characteristic frequencies at which absorption takes place. For ordinary conduction/ space charges this frequency is zero (Drude), for dipole orientation there is a range of frequencies up to the microwave and finally ionic and electronic transitions occur in the IR and UV part of the spectrum.
Now the real part of the dielectric constant can be obtained from this absorptive part by a Kramers Kronig transformation.
 
DrDu said:
I would rather say they decrease in that order!
In general the maximal frequency depends on the inertia of the degrees of freedom. It is clear that an ion can't move as fast as an electron as it is heavier.
A more elaborate argument goes like this: The degrees of freedom have characteristic frequencies at which absorption takes place. For ordinary conduction/ space charges this frequency is zero (Drude), for dipole orientation there is a range of frequencies up to the microwave and finally ionic and electronic transitions occur in the IR and UV part of the spectrum.
Now the real part of the dielectric constant can be obtained from this absorptive part by a Kramers Kronig transformation.

The lower frequency of interface and dipole polarization, in that order, relative to ionic polarization is what I'm having trouble with. I'm not sure why interfacial polarization occurs at the lowest frequency or why dipole/orientation polarization occurs at a higher frequency than interfacial, but a lower frequency than ionic.
 
Interface polarization is due largely to classical currents of charge which are described by the Drude formula, i.e. a resonance at zero frequency. Dipole orientation is rotational motion of the dipoles which has resonance poles in the microwave/ far IR. "Ionic" polarization refers to the polarization due to optical phonons whose resonance frequency is in the IR.
 
DrDu said:
Interface polarization is due largely to classical currents of charge which are described by the Drude formula, i.e. a resonance at zero frequency. Dipole orientation is rotational motion of the dipoles which has resonance poles in the microwave/ far IR. "Ionic" polarization refers to the polarization due to optical phonons whose resonance frequency is in the IR.

Ok, I think I can figure out the dipole/ionic polarization from here, but I haven't seen anything relating Drude to interface polarization. Do you have any references describing this?
 
No, I have no reference. But as far as I understand, boundary polarization is an effect describable using ordinary macroscopic electrodynamics. So you can write down some equivalent RC networks etc whose characteristic frequencies are very low compared to the other effects mentioned.
Also the characteristic frequency of the conductivity which determines the R is 0, at least in Drude theory.
 

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