All About Dielectric Materials

William Whewell was the first to coin the word “dielectric.” It comprises two words: ‘Dia’ and ‘Electric.’ A dielectric material is a substance that conducts electricity poorly but effectively supports an electrostatic field. An electrostatic field can store energy if the flow of current across opposing electric charge poles is reduced to a minimum and the electrostatic lines of flow are not obstructed or interrupted. Capacitors benefit from this property. 

Radio-frequency transmission lines are also constructed with dielectric materials. Most dielectric materials are solid in practice. Porcelain, glass, polymers, and metal oxides are just a few examples. 

Dielectric materials can be found in some liquids and gases. Variable capacitors and certain types of transmission lines employ dry air as a dielectric. Distilled water has a good dielectric property. Now that we know what dielectric materials are, let us know about polar molecules and non-polar molecules.

Polar Molecules and non-polar Molecules

·  Polar Molecules

When each molecule’s positive and negative charge centres in a dielectric substance do not coincide, the dielectric substance is referred to as a polar dielectric.

For example, Water.

·  Non-polar Molecules

Because of the symmetry of molecules, non-polar dielectric substances are those in which there is a coincidence of the centres of positive and negative charge of each molecule.

For example, Oxygen.

Dielectric Material Types

The type of molecule contained in the material is used to classify dielectrics. Polar dielectrics and non-polar dielectrics are the two types of dielectrics.

1. Polar Dielectrics

The centre of mass of positive ions does not correspond with the centre of mass of negatively charged particles in polar dielectrics. The dipole moment occurs here. The shape of the molecules is uneven. When the electric field is supplied, the molecules align up with the electric field. When the electric field is removed, the molecules exhibit random dipole moments, and the net dipole moment in the molecules is zero.

2. Non-Polar Dielectrics

The centres of mass of both negative and positive particles coincide in non-polar dielectrics. These compounds do not have a dipole moment.

Properties of Dielectric Materials

A perfect dielectric has no electrical conductivity. A dielectric, like an ideal capacitor, stores and dissipates electrical energy. The following are some of the most important properties of a dielectric material:

1. Dielectric Polarisation

An electric dipole moment is measured by the distance between positively and negatively charged in a system. The dielectric properties are defined by the relationship between the dipole moment (M) and the electric field (E). The atom returns to its native state whenever the applied electric field is removed. This occurs in a way that is exponentially decaying. Relaxation time is when it takes for an atom to return to its original state.

2. Electric Susceptibility

The electric susceptibility of a dielectric substance is a distribution of how quickly it can be polarised when discovered in an electric field. This value also determines the material’s electric permeability.

3. Total Polarisation

Two things determine the polarisation of a dielectric. The generation of dipole moments and their orientation to the electric field are what they are. Ionic polarisation can be attained by relying on the type of elementary dipole. Electronic polarisation occurs when the dielectric molecules that compose the dipole moment are formulated of neutral particles.

4. Dielectric Dispersion

When P is the dielectric’s maximum polarisation, tr is the relaxation time for a specific polarisation process. Several polarisations have different relaxation times.

5. Dielectric Breakdown

The insulator begins to conduct and behaves like a conductor when larger electric fields are applied. Dielectric materials lack their dielectric characteristics in such situations. Dielectric Breakdown is the term for this phenomenon. It’s an unstoppable process. Dielectric materials fail as a result of this.

Uses of Dielectric Materials

Dielectrics are used in a wide range of applications; a few of them are as follows:

·  These are used in capacitors to store energy.

·  Highly conductive dielectric materials are utilised to improve the performance of semiconductor devices.

·  Mineral oils are utilised as a liquid dielectric in electrical transformers and aid in cooling.

·  Castor oil is used to improve the capacitance of high-voltage capacitors.

·  The electrostatic equivalent of Electrets is a carefully treated dielectric substance.

·  Liquid Crystal Displays make use of dielectrics.

·  In a Dielectric Resonator Oscillator, the ceramic dielectric is used.

·  Strontium barium Titanate thin films are dielectric and are utilised to provide great tunability and low leakage current in microwave tunable devices.

·  Parylene is a chemical used in industrial coatings to bridge a gap between the substrate and the outside world.

Conclusion

Dielectrics are materials in which an electrical field can persist for a long time and are responsive to electromagnetic waves in the optical range; hence, electromagnetic energy distributes, breaks down, absorbs, collects, and can be converted into dielectrics. One of the most crucial characteristics of dielectrics is electrical polarisation, and their electrical conductivity is relatively low.