Qualitative explanation of paraelectricity

  • Thread starter Papow
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Hello,

I am wondering what is qualitatively speaking the effect that causes a material to be paraelectric? I do know that it strengthens an applied external electric field with alignment of electric dipoles. What is the mechanism that causes this alignment of dipoles? In a traditional dielectric material the external electric field creates alignment of dipoles in the opposite direction compared to a paraeletric material, so that the material weakens the external field.

Thank you,

Tatu
 

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  • #2
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Paraelectrics and dielectrics are the same thing. Even in a dielectric, the dipoles align with the field, not against it.

Perhaps you are thinking of the field created by those dipoles? Inside the material, that field is opposite the direction of the external field, making the field weaker inside the material. (In the limiting case where the dielectric becomes a conductor, it cancels the field completely inside the material.) Outside the material, the field actually becomes stronger.
 
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Thanks for the response! This made things clearer for me; dielectricity and paraelectricity are in principle the same thing. However, it seems to be that the difference between normal dielectricity and paraelectricity is that paraelectric materials have a non-linear polarization dependence on relatively small external E-fields.

The P-E graphs for dielectric and paraelectric polarization can be found here:
http://en.wikipedia.org/wiki/Ferroelectricity" [Broken]

Tatu
 
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