ABSTRACT
Dielectric materials in the form of ceramics or polymers are characterized by the fact that they contain virtually no free charges and therefore are electrical insulators. The lack of free charge implies a bandgap energy that is at least large enough to prevent thermal ionization of electrons and is generally high enough for them to be transparent in the visible spectrum. However, just because their conductivity is small, the electrical and optical properties of dielectrics are by no means uninteresting. The presence of an electric field distorts the atoms and molecules so that the center of their positive charge is displaced from the center of their negative charge and electric dipoles are formed. The electrical and optical properties are determined primarily by the dielectric material’s ability to form electric dipoles in the presence of an electric field. But, since one of the dielectric’s primary functions is that of an electrical insulator, we shall consider this attribute first.
