The phenomenon in which a displacement of bound charges of a limited magnitude occurs in a dielectric, or a rotation of electric dipoles is observed , is called the polarization of dielectrics in physics. The course of this process can occur either spontaneously, for internal reasons, or under the influence of external forces, primarily electric fields.
The physical and mathematical reflection of the process is characterized by a polarization vector, which is a dipole moment, which is considered in relation to the volume of the dielectric. 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.
Based on this statement, we can formulate a general symptom of the phenomenon. This state of the dielectric, in which it reveals the presence of a dipole moment at each point of its volume, characterizes the polarization of dielectrics.
The phenomenon under consideration is ambiguous in nature. 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 pathogens, mechanical (ferroelectric), formed under the action of mechanical pathogens, thermal, arising under the influence of temperature fluctuations.
A feature of polarization as a physical phenomenon is that it practically does not affect the total charge of a homogeneous dielectric, no matter what point of its volume is chosen. At the same time, during polarization, the formation of bound charges on the surface of the dielectric. These charges are sources of an additional field with a certain intensity, the vector of which is directed against the action vector of the external field.
An important issue under consideration is the classification of the polarization of dielectrics depending on its mechanisms themselves. In this aspect, its types are distinguished:
- Migration is typical for materials in the structure of which there are clearly distinguishable layers with different conductivities. Such 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;
- the ionic one is characterized by the same factors as the electronic one, only in this case there is not a displacement of the shells of the atoms, but a displacement of the structural nodes of the crystal lattice of substances;
- dipole, or as it is also called orientational polarization, is characterized by significant losses, the reason for which is the large expenditure of energy to overcome internal bonds in the dielectric. The orientational polarization of dielectrics is characterized by the phenomenon of a strictly defined orientation of dipoles;
- electronic relaxation is characterized by the presence of the same specific orientation of defective electrons;
- ion-relaxation polarization of dielectrics is manifested in the movement of ions that have weak internal bonds and are not fixed stably at the nodes of the crystal lattices of the structure of the substance;
- structural is also manifested in a certain orientation of the dielectric elements, but in this case, various impurities that the dielectric substance contains are these elements. 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, such a name.
As a rule, in all cases, except for resonant polarization, its value reaches maximum values in static fields.