Question

Describe the poling and depoling process of a material, respectively, for a ferroelectric material(s)?

Answer 1

We know that ferroelectric materials are those which has "spontaneous electric polarization" which can be changed by the application of external electric field. Ferromagnetic material has non-linear polarization dependance on external electric field and also at zero external electric field it has non-zero polarization.

So poling of a ferroelectric materials involves "application of strong electric field". What we do for poling is, we heat the ferroelectric material above its Curie temperature. At this stage the material loses its spontaneous polarisation. And then we apply strong external electric field to it and so that aligns all the randomly oriented electric dipoles to get aligned in the direction of external electric field. And this all together give rise to non-zero stronger polarisation.

Before heating we have domains of electric dipoles. They together give rise to non zero polarisation.

After application of external electric field above Curie temperature we get such aligned pattern.

And this whole process is called "Poling".

While "Depoling" is simply opposite to this process. We simply break this artificial alignment of electric dipoles. Say for example, by means of heating above Curie temperature or applying extreme electro-magnetic fields or even some other mechanical condition. After depoling we may get back to domain pattern as given above in the picture or we may even lose the spontaneous polarization depending on the process used to depole and material used.

But in simple words, depoling is just "breaking of alignment obtained in the process of poling".

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