Dielectric Properties of Solids

Introduction

The solids which do not allow the flow of electric charge when kept in an electric field are known as dielectric solids. They arrange themselves in such a way that their net dipole moment becomes zero. It happens because in strong electric fields the nucleus and the electrons in the solid are pulled at the opposite sides of the solid and create dipoles in the molecule. In this article, we are going to discuss what are dielectric materials and the properties of dielectric properties of solids.

What are Dielectric Materials?

The dielectric materials are electrical insulators, when they are placed in an electric field no charge flows into them. When they are placed in an electric field, they show polarisation. The positive charge on the nucleus slightly moves towards equilibrium and the negatively charged electrons move towards the opposite direction of the electric field. It creates polarisation in the material means, which creates a strong internal field that reduces the overall effect of an electric field in the material. The dielectric molecules contain weekly bonded molecules.

Dielectric Material

Difference Between Dielectric Materials and Insulators

As we read dielectric materials are insulators but not all the insulators are dielectric materials. There are some differences between dielectric materials and insulators. Let's check them −

Dielectric Materials	Insulators
The dielectric materials are easily polarised but do not conduct electricity	They conduct electricity
They have weak bonds within the molecules	They have strong bonds within the molecules
They develop an internal electric field that nills the effect of the external electric field	They can’t develop such a field in the molecules.
Example: they are used in capacitors, transformers, power cables, etc.	Example: They are used in electric appliances, high voltage wires, etc.

Dielectric Materials

The dielectric materials develop an internal electric field within themselves, which reduces the impact of the electric field in them. They get polarised and store charges within them. They are used in capacitors, transformers, power cables, etc. They are also used to store energy. The dielectric materials are of two types. The polar dielectric and non-polar dielectric material.

• Polar Dielectric material − The polar dielectric material shows a dipole moment in the material. Their centre of mass is positively charged and the negative part does not coincide. They are asymmetric in shape. Examples are Hydrochloric acid and Water.

• Non-Polar Dielectric Material − the non-dielectric materials do not show dipole moment and are symmetrical in shape. The centre of the mass is positively charged and the negative part coincides. Examples are Mica, Metal Oxides, Glass, Ceramic, Mica, etc.

Dielectric materials are mainly found in solids but are also found in liquid and gas forms. Some examples of liquid and gas dielectric materials are as follows.

• Liquid Dielectric Material: Distilled Water

• Gas Dielectric Material: Vacuum, Dry Air, Nitrogen, and Helium.

Characteristics of Dielectric Materials

The dielectric materials have the following properties −

• They are electrically susceptible. When they are placed in the electric field they get polarised.

• They show dipole moments. When they are placed in the electric fields, positive and negative charges arrange themselves within the material and create dipoles.

• They show electronic polarisation i.e. when we place dielectric material in an electrical field it forms a dipole moment and becomes neutral.

• The dielectric material shows the dielectric breakdown. When the flow of electricity increases in the material, the electrostatic field becomes too intense. And it starts conducting the electricity. This is called dielectric breakdown.

• The dielectric materials return to their previous state after the electric field applied is removed.

• They show electrical permeability, as when they are kept in the electric field they get polarised.

Dielectric properties of Solids

When the dielectric materials are kept in the electric field the positive charge is slightly moved in equilibrium and the negatively charged electrons are moved to the opposite direction of the electronic flow. Due to this, a dipole is generated in the molecule. And the molecule gets polarised. As per the alignment of dipoles, there may be no dipole in crystals, but only ions will be present. Due to polarisation in the molecule, solids material shows some properties. They are as follows −

• Piezoelectricity

• Ferroelectricity

• Anti-ferroelectricity

• Pyroelectricity

Piezoelectricit

The word piezo is derived from the word piezein to press or squeeze. Some solid materials when kept in the electric field align themselves in an ordered way so that the dipole moment in the solid shows piezoelectricity means when any mechanical stress is applied to the solid it converts into electric energy and vice versa.

The best example is lighter. In a lighter when the button is pressed due to pressure it lits. These materials are also used in ultrasonic devices, microphones, sonar detectors, the automobile industry, also used in mechanical and automotive industries, etc. Examples are quartz, ammonium dihydrogen phosphate (NH₄ H₂ PO₄), etc.

Ferroelectricity

In some materials, the dipoles are permanently aligned with either electric field present or absent. They are known as ferroelectric materials. In these materials when we apply electric fields the direction of polarisation is changed.

These materials are used in capacitors, ultrasound imaging, filters, modulators, etc. Examples of ferroelectricity materials are Barium Titanate (BaTiO₃) Sodium and potassium salt of ferroelectric materials, Potassium Dihydrogen Phosphate (KH₂ PO₄), Rochelle salt, etc.

Anti-ferroElectricity

As the name suggests these materials are the opposite of ferroelectric materials. They show zero polarisation, as the dipoles are aligned but oriented in opposite directions. So the net dipole becomes zero. The strength and weakness of antiferroelectric materials can be altered by changing the temperature, pressure and external electric fields applied. An example of anti-ferroelectricity is Lead Zirconate (PbZrO₃).

Pyroelectricity

Some materials produce electricity on heating these materials are known as pyroelectricity materials. Pyroelectricity is derived from the word Pyr which means ‘fire’. The energy produced through these materials is called pyroelectricity and the process is known as a pyroelectric effect.

These materials are used in thermal sensors, infrared non-contact thermometers, power generation, motion detectors in animals, human beings, and other objects, etc.

Conclusion

In this article, we have read that the dielectric material is a poor conductor of electricity, and they show polarisation when kept in an electrical field. They show the property of electric susceptibility, dielectric polarisation, dipole moment, etc. Get through examples what is the difference between a dielectric material and an insulator. The material which has a low dielectric constant are perfect dielectric materials, which show low conductivity in electric fields like dry air, vacuum, helium and nitrogen gas, etc. the orientation of dipoles in dielectric materials shows different properties in them like piezoelectricity, pyro-electricity, Ferroelectricity, and anti-ferroelectricity. How the dielectric materials are helpful in our lives like conductors, transformers, automotive and electrical industries, etc.

FAQs

1. What is the use of dielectric material in capacitors?

The dielectric material is used in capacitors to reduce the strength of the electric field between the plates in capacitors. It helps in reducing the sparking or shorting at high voltage.

2. What is a perfect dielectric material?

The perfect dielectric material is that which has no conductivity. An example of perfect dielectric material is dry air.

3. What are the uses of dielectric material?

The dielectric material is used in capacitors, transformers, sensing devices, motion detectors, thermometers, automotive industries, sonar detectors, etc.

4. Who discovered the ferroelectric materials?

The ferroelectric materials were discovered by Valasek in the material Rochelle Salt.

5. What are the uses of Ferroelectric materials?

The ferroelectric materials are used in capacitors, infrared cameras, fire sensors, Ferroelectric RAMs, fuel injectors, etc.