Dielectric Properties: Definition, Properties of Dielectric and Examples

In Dielectric materials when allowed to subject to the electric field the positive charges in the material gets displaced in the direction of the applied electric field. The negative charges are shifts in the direction opposite to the applied electric field. This leads to dielectric polarization. Basically, electric charges do not flow through the material. Polarization reduces the field of the dielectric. Learn dielectric properties here.

Dielectric properties

Properties of Dielectric

The term Dielectric was first given by William Whewell. The electrical conductivity of a perfect dielectric material is zero. A dielectric store and dissipate the electrical energy similar to an ideal capacitor. Some of the main properties are Electric Susceptibility, Dielectric polarization, Dielectric dispersion, Dielectric relaxation, Tunability and many more.

Electric Susceptibility

The dielectric material can easily be polarized when subjected to an electric field. It is measured by electric susceptibility. It also determines the electric permeability of the material.

Dielectric Polarization

An electric dipole moment is a measure of separation of negative and positive charge in the system. The relationship between the dipole moment i.e., M and the electric field i.e., E gives rise to the properties of dielectric. When the applied electric field is removed, the atom returns to its original state. This return to the original state happens in an exponential decay manner. The time taken by the atom to reach its original state is Relaxation time.

Total Polarization

The factors that decide the polarization of dielectric is the formation of dipole moment and their orientation that is relative to the electric field. According to elementary dipole type, there can be either electronic polarization or ionic polarization. Electronic polarization i.e., \(P_e\) occurs when the dielectric molecules forming the dipole moment are of neutral particles.

Ionic polarization \(P_i\) and electronic polarization both are independent of temperature. Permanent dipole moments in the molecules is an asymmetrical distribution of charge between different atoms. In such cases, orientational polarization \(P_o\) is observed. If a free charge is there in the dielectric material it may lead to the Space charge polarization \(P_s\). Thus, the total polarization of the dielectric material is given below:

\(P_{Total} = P_i + P_e + P_o + P_s\)

Dielectric Dispersion

P is the maximum polarization attained by the dielectric material. T_r is the relaxation time for a particular polarization process. The dielectric polarization process is expressed as

P(t) = P[1-exp(-t/tr)]

The relaxation time of the material varies for different polarization processes. Electronic polarization is followed by ionic polarization. An orientation polarization is slower than ionic polarization. Space charge polarization is very slow.

Dielectric Breakdown

When higher electric fields are provided then the insulator starts conducting and it behaves as a conductor. In such cases, dielectric materials lose their dielectric properties. This phenomenon is Dielectric Breakdown. Dielectric Breakdown is an irreversible process. This process leads to the failure of dielectric materials.