The phenomenon at which occurs in a dielectricbounded by the magnitude of the displacement of bound charges, or the rotation of electric dipoles is observed, was called in the physics the polarization of dielectrics. The flow of this process can occur either spontaneously, for internal reasons, or under the influence of external forces, primarily electric fields.
Physico-mathematical reflection of the processis characterized by a polarization vector representing a dipole moment, which is considered in relation to the magnitude of the dielectric volume. Quite often in the physical context a simplified term is used - polarization. This parameter is used not only to reflect the macroscopic state. It can be used to describe any phenomena that have properties that characterize the polarization of dielectrics.
Proceeding from this statement, it is possible to formulatecommon sign of the phenomenon. Such a state of the dielectric, in which the presence of a dipole moment in each point of its volume is detected in it, characterizes the polarization of dielectrics.
The phenomenon under consideration is ambiguous in itsnature. There are such types of polarization of dielectrics as induced, that is, arising under the influence of external electric fields, spontaneous, formed in the absence of external polarization exciters, mechanical (ferroelectric), formed under the action of mechanical exciters, thermal arising under the influence of temperature fluctuations.
A feature of polarization as a physical phenomenonis that it practically does not affect the value of the total charge of a homogeneous dielectric, no matter what point of its volume is chosen. At the same time, during the polarization, bound charges are formed on the surface of the dielectric. These charges are the sources of an additional field with some intensity, the vector of which is directed against the vector of action of the external field.
Important in this issue is the classification of the polarization of dielectrics, depending on the mechanisms themselves. In this aspect, its types are distinguished:
- Migration is characteristic for materials in the structure of which there are clearly distinguishable layers with different conductivity. Such a polarization is characterized by a delayed action;
- Electronic polarization consists in the movement of the shells of atoms under the influence of external electric fields. This is the fastest type of polarization;
- ionic is characterized by the same factors as the electronic one, only in this case there is not a displacement of the shells of atoms, but the displacement of the nodes of the structure of the crystal lattice of substances;
- dipole, or as it is calledorientational polarization is characterized by significant losses, the reason of which is a large expenditure of energy to overcome internal bonds in the dielectric. For orientational polarization of dielectrics, the phenomenon of a strictly defined dipole orientation is characteristic;
- Electron-relaxation is characterized by the presence of the same definite orientation of defective electrons;
- ion-relaxation polarization of dielectricsis manifested in the movement of ions, which have weak internal bonds and are not fixed stably at the nodes of the crystal lattices of the structure of matter;
- structural is also manifested in a certainorientation of the elements of the dielectric, but in this case these elements are various impurities that contain the dielectric material. This polarization proceeds most slowly;
- Spontaneous (spontaneous) is observed in dielectrics with very high permeability parameters, they are called ferroelectrics;
- resonance is characterized by the coincidence of the frequencies of the electrons of the dielectric with the frequencies of the field acting on it, hence, in fact, and this name.
As a rule, in all cases, except resonant polarization, its magnitude reaches its maximum values in static fields.
