Relaxation times/frequencies of Polarization Mechanisms

In summary: So charge motion does not contribute to interface polarization.In summary, 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
  • #1
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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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  • #2
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.
 
  • #3
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.
 
  • #4
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.
 
  • #5
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?
 
  • #6
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.
 

FAQ: Relaxation times/frequencies of Polarization Mechanisms

What is the definition of relaxation time/frequency of polarization mechanisms?

The relaxation time/frequency of polarization mechanisms refers to the characteristic time/frequency it takes for the electric dipole moments of molecules or atoms to return to their original equilibrium state after being perturbed by an external electric field.

How is relaxation time/frequency related to the dielectric properties of a material?

The relaxation time/frequency is directly related to the dielectric properties of a material. As the relaxation time/frequency increases, the dielectric constant also increases, indicating that the material can store more electric charge.

What are the different types of polarization mechanisms and their corresponding relaxation times/frequencies?

The three main types of polarization mechanisms are electronic, ionic, and orientational. The relaxation time/frequency for electronic polarization is in the order of femtoseconds, for ionic polarization it is in the order of nanoseconds, and for orientational polarization it is in the order of microseconds.

How does temperature affect the relaxation time/frequency of polarization mechanisms?

The relaxation time/frequency of polarization mechanisms is strongly influenced by temperature. As temperature increases, the relaxation time/frequency decreases due to increased molecular motion and higher thermal energy, making it easier for molecules to return to their equilibrium state.

What factors can cause changes in the relaxation time/frequency of polarization mechanisms?

The relaxation time/frequency of polarization mechanisms can be affected by several factors, including the type of material, temperature, frequency of the applied electric field, and the strength of the electric field. Additionally, impurities, defects, and external stress can also impact the relaxation time/frequency.

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