# Dielectric Properties of Solid

Now, it is known that electricity or electric current is considered as the flow of negatively charged atoms, i.e. electrons, from one terminal to another(positive or negative terminal). As the stream of electrons, i.e. current flows through various materials, some substances show resistance to the current flow while others do not. This property of substances to resist the flow of current is known as resistivity. Thus, objects or substances that carry electricity can be classified as conductors or insulators. Conductors are substances that do not show resistivity to the electric current, whereas insulators show resistivity to the electric current.

However, a shift is observed when electricity is passed through insulators even though they do not possess the capability to contain the electric current through them. Such insulators that display a change in their structure are known as dielectric materials or dielectric substances. In simple words, an electrical insulator material or insulating substance that the application of an electric field can polarize is called a dielectric or a dielectric material. This property of dielectric materials is most commonly observed in insulators. For instance, if we keep an insulator in an electric field, it undergoes a shift in its orientation. The negatively charged electrons, positively charged protons, and nucleus move from their equivalent equilibrium positions. The application of electric fields causes them to move in opposite directions, i.e. the positively charged atoms or protons move on one side of the material.

In contrast, the negatively charged atoms or electrons move on the other side. So, precisely speaking, the positive charges are shifted towards the orientation(direction) of the electrical field, and the negative charges are shifted in an orientation(direction) opposite to that of the electrical field. This also implies that the positively charged nucleus is polarized in the orientation(direction) of the electrical field. Moreover, the negatively charged electrons are too polarized in the opposite direction of the electrical field.

## Types of Dielectric Properties

The different types of dielectric properties of solids are:-

## 1. Pyroelectricity

The ability of certain substances to generate electricity, such as crystals, if they are cooler or under the application of heat is called Pyroelectricity. Some of these pyroelectric solids or crystals can also produce electricity under different conditions. The phenomenon is known as the pyroelectric effect, as the electricity generated in these crystals is known as Pyroelectricity.
Pyroelectric crystals are also used in appliances such as heat sensors or in the process of power generation and nuclear fusion. They are also used in PIR (passive infrared) sensors, infrared non – contact thermometers, thermal or motion detection sensors that work on heat, etc. Thus, Pyroelectricity has applications in several fields.

## 2. Piezoelectricity

These are the type of solids where the individual dipoles are generated, due to which we can observe that the atoms in these materials align themselves in an orderly manner. The orientation in these materials is so that the net dipole moment of the solid shows piezoelectricity is known as piezoelectric materials. Whenever the solid is under pressure, its constituent atoms are observed to be displaced from their initial position, which produces electricity. This property of solids has a variety of applications. Its applications are seen in the automotive industry and the medical field.

## 3. Ferroelectricity

In Ferroelectric solids, the dipoles formed within the constituent atoms are observed to be permanently aligned even in the absence of an electric field. Therefore, these solids or crystals possess electric polarization that can be generated spontaneously. On application of an external electric field on such solids, this electrical polarization may get reversed. These ferroelectric crystals are used in infrared cameras, capacitors, fire sensors, and vibration sensors.

## 4. Anti – ferroelectricity

Solids that are observed to possess anti – ferromagnetism properties are known to consist of an ordered array of electric dipoles. However, these dipoles contain slightly different structures as compared to substances such as ferroelectric crystals. The adjacent dipoles are observed to have opposite directions to each other. This orientation of the dipoles results in a total zero dipole moment of the constituent atoms. Thus, we can conclude that anti-ferroelectric solids possess zero electric polarization generated spontaneously as every adjacent dipole in the anti-ferroelectric crystal cancels each other.
This property of the solids can be generated or removed depending on specific parameters such as temperature, pressure, external electric field, etc. The temperature where these crystals' anti–ferroelectricity seems to disappear is called the Neel point or the Curie point. These crystals are primarily used in integration with materials that possess ferromagnetism.

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