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What is Dielectric Constant? Properties of Dielectric Materials

Take a look around your kitchen; did you notice any shared characteristics between the fired cookware or utensils and glass, plastic, mica, or even the air? Did you consider making an electronic segment out of them? Almost certainly not! Because the properties of these materials are frequently overlooked. In this article, we will go over the dielectric materials in depth, also we will discuss what is dielectric constant and its applications.

What is Dielectric material?

What is Dielectric Constant? Properties of Dielectric Materials

A dielectric or dielectric material or dielectric medium in electromagnetism is an electrical insulator that can be polarized by an applied electric field. When an electric field is applied to a dielectric material, electric charges do not flow through the material as they do in an electrical conductor because there are no loosely bound, or free, electrons that can drift through the material, but instead shift slightly from their average equilibrium positions, resulting in dielectric polarization. Positive charges are displaced in the direction of the field by dielectric polarization, while negative charges shift in the opposite direction. This produces an internal electric field, which lowers the overall field within the dielectric. When a dielectric is made up of weakly bonded molecules, they become polarized and reorient so that their symmetry axes align with the field. Dielectric properties are concerned with the storage and dissipation of electric and magnetic energy in materials. Dielectrics play an important role in explaining a variety of phenomena in electronics, optics, solid-state physics, and cell biophysics.

Properties of Dielectric Material

The dielectric materials exhibit the following properties:

  • The energy gap in dielectric materials is vast.
  • The insulation resistance is high and the temperature coefficient of resistance is negative.
  • The resistivity of dielectric materials is high.
  • The electrons have a strong attraction to the parent nucleus.
  • These materials have very low electrical conductivity because there are no free electrons to carry current.

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What is dielectric constant?

What is Dielectric Constant? Properties of Dielectric Materials

The dielectric constant is critical information to have when designing thin film capacitors and other materials that are expected to introduce capacitance into a circuit. A thin film capacitor made of the test film is used to measure it. The dielectric constant is the ratio of a capacitor’s capacitance with test material as the dielectric to a capacitor’s capacitance with vacuum (or air) as the dielectric. The dielectric constant of films intended for electrical insulation should be low. The dielectric constant of films used as dielectrics in capacitors should be high in order to minimize capacitor dimensions. Temperature and current frequency have an effect on the dielectric constant.

The dielectric constant is a property of an electrical insulating material (a dielectric) equal to the ratio of the capacitance of a capacitor filled with the given material to the capacitance of an identical capacitor in a vacuum without the dielectric material. Inserting a dielectric between the plates of a parallel-plate capacitor, for example, always increases its capacitance, or ability to store opposite charges on each plate, when compared to when the plates are separated by a vacuum.

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If C is the capacitance of a capacitor filled with a given dielectric and C0 is the capacitance of an identical capacitor in a vacuum, the formula of dielectric constant is given as

κ = C / C0

The dielectric constant is a dimensionless quantity i.e. there is no unit of dielectric constant. The dielectric constant and permittivity are the same in the CGS system. It refers to a large-scale dielectric property without specifying the electrical behavior on the atomic scale. Any material’s static dielectric constant is always greater than one, the value for a vacuum. At room temperature, the dielectric constant of air is 1.00059 and dielectric constant of water is 78.2. Because the dielectric constant of air is nearly the same as that of a vacuum, air does not increase the capacitance of a capacitor in any practical sense. The dielectric constants of liquids and solids can be calculated by comparing the capacitance when the dielectric is present to the capacitance when the capacitor is filled with air.

The dielectric constant is the ratio of a substance’s permittivity to that of free space. It is the electrical equivalent of relative magnetic permeability and expresses the extent to which a material concentrates electric flux. If all other factors remain constant, the electric flux density increases as the dielectric constant increases. This allows objects of a certain size, such as sets of metal plates, to retain their electric charge for extended periods of time and/or in large quantities. High dielectric constant materials are useful in the production of high-value capacitors.

A high dielectric constant is not necessarily desirable in and of itself. Substances with high dielectric constants generally degrade faster when subjected to high electric fields than materials with low dielectric constants. Dry air, for example, has a low dielectric constant but works well as a dielectric material in capacitors used in high-power radio-frequency (RF) transmitters. Even if air experiences dielectric breakdown, the breakdown is not permanent. Air returns to its normal dielectric state when the excessive electric field is removed. However, solid dielectric materials such as polyethylene or glass can sustain permanent damage.

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Applications of dielectrics

Solids, liquids, and gases can all be dielectric materials. Solid dielectrics are the most common dielectrics used in electrical engineering, and many solids are excellent insulators. Porcelain, glass, and most plastics are dielectric material examples. The three most common gaseous dielectrics are air, nitrogen, and sulfur hexafluoride.

  • Dielectrics are used to store energy as capacitors.
  • Some dielectrics can generate a potential difference when subjected to mechanical stress, or (equivalently) change physical shape when an external voltage is applied across the material. This is known as piezoelectricity. Another type of useful dielectric is piezoelectric materials.
  • A transformer’s dielectric material serves as both an insulator and a cooling agent.
  • Industrial coatings, such as Parylene, act as a dielectric barrier between the substrate and its surroundings.  
  • High permittivity dielectric materials are used to improve the performance of a semiconductor device.
  • Because dielectrics resist the flow of electricity, their surfaces can hold stranded excess electrical charges. This can happen by accident when the dielectric is rubbed (the triboelectric effect). This can be beneficial, as in a Van de Graaff generator or electrophorus, or potentially destructive, as in electrostatic discharge.
  • Electrets are dielectric materials that have been processed to act as an electrostatic equivalent to magnets.
  • Some ionic crystals and polymer dielectrics have a spontaneous dipole moment that can be reversed by applying an external electric field. The ferroelectric effect describes this behavior. These materials behave similarly to ferromagnetic materials in the presence of an external magnetic field. Ferroelectric materials frequently have extremely high dielectric constants, making them ideal for capacitors.
  • Mineral oil is widely used as a fluid dielectric and to aid in cooling inside electrical transformers. Higher dielectric constant dielectric fluids, such as electrical grade castor oil, are frequently used in high voltage capacitors to help prevent corona discharge and increase capacitance.
  • Specially processed dielectrics, known as electrets, can retain excess internal charge or “frozen in” polarization. Electrets, the electrostatic equivalent of magnets, have a semi-permanent electric field.

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