Polarization, the Electrical Distortion in Matter

The blocked or restricted motion of the charges in a body of matter appears to the experimenter as a polarization response. The continuous or semicontinuous motion of such charges through the sample appears as a conductive response. The two processes are linked over the entire frequency range by the Kramers-Kronig relations. This is well discussed in Frohlich s book on dielectrics. 

The so-called atomic polarization arises from the shifts of differently charged atoms with respct to each other. In salt, NaCl, for example, which is an ionic solid, an applied external field causes the positive sodium atoms to shift their positions slightly with respct to their negative counterparts. Normally such a contribution to the dielectric polarization of solids is low, about 1/7 that noted for the electronic polarization in organic materials. In rare cases, atomic polarization can be quite large. Witness, for example the perovskite minerals such as BaTi03. It may, if prepared carefully, have a remarkably high relative dielectric constant of, say, 4000. 

As the name implies, this arises from the orientation of dipolar molecules or portions thereof That is, since the various atoms comprising a molecule may carry somewhat differing net charges, there will be regions 

A given field strength produces a polarization proportional to the number of dipoles per unit volume, and to the degree to which the charges in the material can be induced to move. Said another way, the wider the domain in which the changes can swing, the greater the effective dielectric constant of the material. 

These concepts can be, perhaps, better appreciated by considering the following simple equation  

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