Dielectric

12 Key excerpts on "Dielectric"

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  Electronic, Magnetic, and Optical Materials

  • Pradeep Fulay, Jung-Kun Lee(Authors)
  • 2016(Publication Date)
  • CRC Press

    (Publisher)

  241 7 Linear Dielectric Materials 7.1 Dielectric MATERIALS A Dielectric material typically is a large-bandgap semiconductor ( E g ~ >4 eV) that exhibits high resistivity ( ρ ). The prefix dia means through in the Greek language. The word Dielectric refers to a material that normally does not allow electricity (electrons, ions, and so on) to pass through it. There are special situations (for example, exposure to very high electric fields or changes in the composi-tion or microstructure) that may lead to a Dielectric material exhibiting semiconducting or metallic behavior. However, when the term Dielectric material is used, it generally is understood that the material essentially is a nonconductor of electricity. An electrical insulator is a Dielectric material that exhibits a high breakdown field. 7.1.1 E LECTROSTATIC I NDUCTION To better understand the behavior of nonconducting materials, let us first examine the concept of electrostatic induction and what is meant by the terms free charge and bound charge . First, con-sider a Dielectric such as a typical ceramic or a plastic that has a net positive charge on its surface. Now, assume that we bring a Conductor B near this charged Insulator A (Figure 7.1a). The electric field associated with the positively charged Insulator A pulls the electrons toward it from Conductor B. This is also described as the atoms in Conductor B being polarized or affected by the presence of an electric field. The process of the development of a negative charge on Conductor B is known as electrostatic induction. In this case, the negative charge developed on Conductor B is the bound charge because it is bound by the electric field caused by the presence of the charged Insulator A next to it. The creation of a bound negative charge on Conductor B, in turn, creates a net positive charge on the other side of the conductor because the conductor itself cannot have any net electric field within it.

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  Handbook of Electrostatic Processes

  • Jen-Shih Chang, Arnold J. Kelly, Joseph M. Crowley(Authors)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  4 Electrical Phenomena of Dielectric Materials R. Tobaz6on Centre National de la Recherche Scientifique Grenoble , France I. INTRODUCTION If we exclude metals, all remaining materials are Dielectrics, whatever the state of the matter in question (solid, liquid, gas), and a permittivity e can be ascribed to any substance, with vacuum as the reference Dielectric. Dielectrics can be employed either as passive devices (capacitors, ca­ bles) or in active devices (electrets, electrostatic motors), and they are required to function in our near or far environment (air, seawater, soil, space). Generally, materials are subjected to a voltage (dc, ac, impulse), and, in exceptional cases, to an electromagnetic field produced by, for example, an intense laser beam. The spatiotemporal distribution of the field inside the matter not only is imposed by the geometry of the elec­ trodes (whether to insure a uniform or a nonuniform field) and the shape of the voltage wave but also depends on space charges: charge carriers can be generated or blocked at interfaces or interphases, when different Dielectric substances come into contact with each other. Among environmental constraints, we may consider the actions of pres­ sure, temperature, radiation, chemical attack, etc. Time is often a funda­ mental parameter in the study of Dielectrics, e.g.: A perfect insulator would be a medium through which no conduction current could flow. In fact, the transition from “capacitive” behavior to “resistive” behavior depends on the conduction relaxation time 51 52 TOBAZEON tc = ep (insofar as a resistivity p can be ascribed to the material). Thus a Dielectric may behave in a completely different manner under dc, ac, or impulse voltages.

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  An Introduction to Electronic and Ionic Materials

  • Wei Gao, Nigel M Sammes;;;(Authors)
  • 1999(Publication Date)
  • WSPC

    (Publisher)

  Seven Dielectric Materials 7.1. Introduction — Dielectric Properties Dielectric materials are insulators as they have a large energy gap between the valence and conduction bands. Thus, the electrons in the valence bands cannot jump to the conduction band. Therefore, the resistivities of these materials are very high. Most ceramics are Dielectric materials and have a mixture of ionic and covalent bonding. Although these materials do not conduct electric current when an electric field is applied, they are not inert to the electric field. The field may cause a slight shift in the balance of charge within the material to form an electrical dipole. Thus, the material is called a Dielectric material. The two important applications of Dielectric materials are electrical in-sulators for preventing electricity transfer and capacitors for the storage of electrical charges. The most important properties of Dielectric materials are: (i) Relative permittivity, e T . (ii) Tangent of loss angle, tan S. (in) Dielectric strength. Other important properties of Dielectrics include: (iv) Ferroelectricity. (v) Piezoelectricity. 148 Dielectric Materials 149 (vi) Electrostriction. (vii) Pyroelectricity. 7.1.1. Permittivity or Dielectric Constant e The capacitance of a parallel plate capacitor (Fig. 7.1), Co, is proportional to the plate area, A, and is inversely proportional to the distance between the two plates, d: Co oc A, and Co oc 1/rf. In a vacuum, Co can be expressed as C 0 =e 0 A/d, (7.1) where 6Q is the permittivity of vacuum and a constant: £o = 8.85xl(r 1 2 F/m. If a Dielectric material is inserted into the plate, Eq. (7.1) should be rewrit-ten as C = eA/d, (7.2) where e is defined as the permittivity of the material. N«|lft» ^ ■ ■ ■ ^ ■ ■ ■ ■ ■ ^ ptati ^*1 V Fig. 7.1. A parallel plate capacitor with Dielectric between the plates.

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  Electric Field

  • Mohsen Sheikholeslami Kandelousi(Author)
  • 2018(Publication Date)
  • IntechOpen

    (Publisher)

  Chapter 4 Dielectrics under Electric Field Liu Hongbo Additional information is available at the end of the chapter http://dx.doi.org/10.5772/intechopen.72231 Abstract The chapter first gives a brief introduction on conduction, polarization, dissipation, and breakdown of Dielectrics under electric field. Then, two of electric field-related applica-tions, Dielectrics for electrical energy storage and electrocaloric (EC) effect for refrigera-tion are discussed. Conclusion and perspectives are given at last. Keywords: Dielectrics, electrical energy storage, electrocaloric refrigeration 1. Introduction Dielectrics are materials that can be polarized by an applied electric field. Polarizability is the essential property for Dielectrics. The term is closely related to insulator. In electrical phenom-ena, insulator is commonly used especially in electronic engineering and electrical engineering, that is, in electronic packaging printed circuit board, electrical wire, high voltage system, and so on. It has a longer history than “ Dielectrics. ” The main property of an insulator is to prevent the flow of current when it is not desired. This means that insulator must have low electrical conductivity and can resist breakdown under high electric field. Physically, insulator is a subgroup of Dielectrics because of the existence of polarization. And Dielectrics can include insulator, semiconductor, and other materials with polarizability. Nevertheless, poor insula-tion could screen the polarizability of Dielectrics under electric field, which makes the polari-zation hard to be “ seen ” by electrical measurement. And in most cases, poor insulation makes Dielectrics useless. Thus, insulating property is commonly expected for Dielectrics.

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  Steady Electric Fields and Currents

  Elementary Electromagnetic Theory

  • B. H. Chirgwin, C. Plumpton, C. W. Kilmister(Authors)
  • 2013(Publication Date)
  • Pergamon

    (Publisher)

  CHAPTER 4 DielectricS 4.1 The effects of a Dielectric In Chapter 1 we defined insulators as substances on which, or inside which, electric charge is unable to move continuously. Experiments show that when a piece of insulating material is introduced into a region where an electric field is already established the field is modified, the distributions of charge and the forces acting on the conductors alter, and the potentials of the con-ductors change. In addition, the insulator itself experiences (ponderomotive) forces ; this is illustrated experimentally when dust particles and small pieces of paper are attracted to a charged body such as a gramophone record. Faraday investigated another electrostatic property of an insulating material^ viz. its effect on the capacitance of a condenser. He found that when the region of the field inside a condenser (e.g. between the plates of a parallel plate condenser, or between the spheres of a spherical condenser) was filled with an insulating substance the capacitance of the condenser was multiplied by a factor K (>1) which he was able to measure. The factor K does not depend upon the charge or potential of the capacitor, but varies from one material to another. Faraday called this factor the specific inductive capacity of the material; the modern name is Dielectric constant. More recently it has been found that, under a wider range of conditions than those of Faraday's, investigations, the Dielectric constant of a given material alters. However, for the steady conditions of an electrostatic field of moderate intensity, K may be taken to be independent of the field quantities. When an insulator is situated in a field which presumably penetrates into the material of the insulator we call the substance of the insulator a Dielectric.

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  Electrons, Neutrons and Protons in Engineering

  A Study of Engineering Materials and Processes Whose Characteristics May Be Explained by Considering the Behavior of Small Particles When Grouped Into Systems Such as Nuclei, Atoms, Gases, and Crystals

  • J. R. Eaton(Author)
  • 2013(Publication Date)
  • Pergamon

    (Publisher)

  CHAPTER 19 Dielectric PROPERTIES OF MATERIALS INTRODUCTION Materials which are non-conductors of electricity find two important uses in the electrical industry, as Dielectric materials in capacitors, and as mechanical supports of energized electrical conductors. In selecting a Dielectric material, the designer is interested in the permittivity of the material, in the losses oc-casioned under anticipated operating conditions and in the Dielectric strength. This chapter will present those microscopic characteristics of material which influence Dielectric permittivity, Dielectric loss, and Dielectric strength. It will be seen that these characteristics are dependent on atomic and molecular structure and so are said to be structure sensitive. Changes in structure due to tempera-ture, pressure, and other causes, may influence profoundly the Dielectric characteristics of materials. 19.1. MACROSCOPIC BEHAVIOR OF DielectricS The influence of the Dielectric material on capacitor behavior is easily illus-trated by a simple experiment. Referring to Fig. 19.1, consider that two con-ducting plates of area A are separated by free space of thickness t. If voltage V + FIG. 19.1. Capacitor plates separated by free space. is applied between the plates, an electric field intensity of ε = Vjt will be estab-lished. From Equations (3.20) and (3.33), one may write q 0 = DQ = KQE. 369 3 7 0 ELECTRONS, NEUTRONS AND PROTONS IN ENGINEERING where q 0 is the surface charge density, D is the electric flux*density,and k 0 is the permittivity of free space. The subscript 0 is used to indicate that the quantities apply to free space. Next suppose that a Dielectric material of permittivity k is placed between the plates, Fig. 19.2, while the voltage V is maintained as before. Charge density, electric flux density, and electric field intensity are now related by q = D = ks k > k 0 . This equation may be rewritten as q = D = k 0 e + (k -k 0 )e.

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  Introduction to the Physics and Chemistry of Materials

  • Robert J. Naumann(Author)
  • 2008(Publication Date)
  • CRC Press

    (Publisher)

  The very thin Dielectric layer that separates the gate from the channel in a FET is very susceptible to breakdown from static charge before the chip is installed in the device. For this reason such chips are shipped in conductive static-proof packages and extreme care in handling such components must be exercised. Unlike the Zener effect in which the breakdown voltage is engineered into the design of the Dielectric, many of the above mechanisms are unpredictable and time-dependent, so the chances of breakdown increases with age. 438 Introduction to the Physics and Chemistry of Materials 23.2 Polarization in Dielectrics As stated previously, the electrical and optical properties are primarily determined by the Dielectric material ’ s ability to form electric dipoles in the presence of an electric fi eld. An electric dipole can be thought of as a positive and a negative charge q separated by some distance d and the dipole moment is de fi ned as p ¼ q d . Macroscopically, the resulting electrical displacement, D ¼ « E ¼ « 0 E þ P , where « is the permittivity, P is the polarization, which is de fi ned as the dipole moment per unit volume, and « 0 is the permittivity of a vacuum ¼ 8.85 10 12 farads = m (Coulomb = V-m). For an anisotropic crystal, « is a tensor of rank two, but here we consider only isotropic materials, so « will be a scalar. It is convenient to de fi ne a relative Dielectric constant « r ¼ « = « 0 . Then « r E ¼ E þ P = « 0 , P ¼ « 0 ( « r 1) E ¼ « 0 x E , where the electric susceptibility x ¼ « r 1. The susceptibility relates the amount of polarization to the applied fi eld, or as the name suggests, tells how susceptible a material is to being polarized by an electric fi eld. 23.2.1 Capacitors To illustrate how Dielectrics interact electrically, we fi rst consider the capacitor, a device for storing electric charge. Basically, a capacitor is simply a sandwich consisting of a Dielectric surrounded by two conductive surfaces.

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  One- and Two-Dimensional Fluids

  Properties of Smectic, Lamellar and Columnar Liquid Crystals

  • Antal Jakli, A. Saupe(Authors)
  • 2006(Publication Date)
  • CRC Press

    (Publisher)

  221 8 Electrical Properties 8.1 Dielectrics Dielectric fluids such as liquid crystals are leaky insulators, i.e., they have low electrical conductivity and polarize in the presence of an electric field . This means that the electric field induces internal charge reorgani-zation, or distortion such as a net electric dipole moment per unit volume P appears. This is the polarization with units C/m 2 . The sign of the polar-ization is defined as P > 0 if the direction is pointing from negative to positive charges. The polarization per unit electric field of an anisotropic material is described by the electric susceptibility tensor as: (8.1) where and ε o = 8.85 × 10 –12 C 2 /Nm 2 (or C/Vm) is the vacuum permittivity. It is usual to define the Dielectric tensor as: (8.2) The reason for introducing is that it gives the electric displacement (its magnitude is the free surface charge per unit area). (8.3) The Dielectric permittivity is a macroscopic quantity; it relates the external electric field to the macroscopic polarization. In the special case of isotropic materials, the tensor becomes a scalar, i.e., E ˆ χ e P E o e α α β β ε χ = α β , , , , = x y z ˆ ε ˆ ˆ ˆ ε χ = + I o e ˆ ε D D P E E E o o = + = + = ε χ ε ε ( ) ˆ 1 E ˆ ˆ . ε ε − → − I 1 222 One- and Two-Dimensional Fluids For uniaxial materials, like ordinary calamitic (rod-shape) nematics, SmA, SmB, the Dielectric tensor is symmetric and has a traceless form in a coor-dinate system fixed to the director: (8.4) where are the components normal and along the director. The eigen-values of the Dielectric tensor are related to the order parameter as: (8.5) and (8.6) where is the Dielectric anisotropy, and is the isotro-pic part of the Dielectric constant, thus independent of the orientational order. Apart from density changes, is typically continuous through all uniaxial liquid crystal phase transitions. A uniaxial material is said to be positive when ε a > 0 and said to be negative when ε a < 0 .

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  Introductory Solid State Physics

  • H.P. Myers(Author)
  • 1997(Publication Date)
  • CRC Press

    (Publisher)

  12 Dielectric Media ‘Insulators’ are Dielectric media, whose general characteristics usually comprise strong ionic or directed covalent bonds, brittle mechanical behaviour at ordinary temperatures, very high resistivities and in many cases transparency to visible and infrared light. A Dielectric is a substance that becomes polarized in the presence of an electric field. The physical quantities of primary interest are the field vectors E and D, the polarization P, together with the electric susceptibility ț and Dielectric constant İ r . If Ǽ denotes the macroscopic electric field within the medium then D=İ r İ 0 Ǽ=İ 0 Ǽ+ȇ , (12.1) ȇ=țİ 0 Ǽ, (12.2) İ r =1+ț. (12.3) An external field acting on a Dielectric produces induced dipole moments, and we must consider the polarizabilities of the atoms; there is therefore some justification for beginning with a treatment of the isolated atom. 12.1 The Free Atom In an isolated atom of Na or Xe, say, the electronic charge is distributed in a spherically symmetrical manner around the nucleus, but in the presence of an external field E 0 the distribution is altered, leading to an induced dipole moment p; we say the atom becomes polarized (Fig. 12.1), and write p=Įİ 0 Ǽ loc , (12.4) where Į is the atomic polarizability (assumed independent of the electric field) and E loc the electric field acting at the site of the atom. We call this the local field. Since a dipole cannot act upon itself and because the atom is isolated, the local field is given in this case by the external field E 0 . The dipole moment arises as a result of separation of the centres of gravity of the electronic and nuclear charges, a separation that is determined by balancing the force Figure 12.1 The basis for an elementary calculation of the polarizability of the free atom. In the presence of the field E 0 the electron charge cloud and the nucleus undergo a slight relative displacement.

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  Interlayer Dielectrics for Semiconductor Technologies

  • Shyam P Muraka, Moshe Eizenberg, Ashok K Sinha(Authors)
  • 2003(Publication Date)
  • Academic Press

    (Publisher)

  Interlayer Dielectrics for Semiconductor Technologies Murarka, Eizenberg and Sinha (Eds.) Copyright © 2003 Elsevier Inc. All rights reserved. Chapter 2 Dielectric properties S.P. Murarka Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA Abstract This chapter reviews the properties of the Dielectric materials with special reference to those used or to be used as the interlayer Dielectrics (ILDs) and forming the insulating layers between the interconnect-lines in one plane or in a multilevel scheme of interconnections in an integrated circuit. All the properties, electrical, mechanical, chemical and electrochemical, and thermal and thermodynamic, have been examined both from fundamental and practical application points of view. The impact of process, actual use, and the interactions with other surrounding materials with which the Dielectric is in contact with, is examined. Both organic and inorganic Dielectrics are considered. Available data on the various properties are listed in various tables for comparison and quick reference purposes. 2.1 Introduction A Dielectric material is defined as a non-conductor of electricity. In other words, it is an effective electrical insulator with very high resistance associated with a large band gap, for example, 8–9 eV for SiO 2 compared to 1.12 for Si. Such materials are, therefore, used as interlayer Dielectrics (ILDs) between two levels of the metal interconnections that interconnect the devices among themselves or to the outside world. There are large number of materials, including oxides, ceramics, nitrides, and polymers, that are electrical insulators and candidates for ILD applica-tions. This chapter examines the properties that are essential in determining this application. The chapter also briefly explores the necessary ILD evaluation techniques and the ranges of applicability.

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  Infrared and Millimeter Waves V8

  Electromagnetic Waves in Matter, Part I

  • Kenneth J. Button(Author)
  • 1983(Publication Date)
  • Academic Press

    (Publisher)

  INFRARED AND MILLIMETER WAVES, VOL. 8 CHAPTER 1 Properties of Dielectric Materials G. W. Chantry National Physical Laboratory Teddington, Middlesex United Kingdom I. II. III. IV. V. INTRODUCTION THE MACROSCOPIC THEORY A. The Response Function B. The Correlation Function and the Cole-Cole Plot C. Corrections for the Internal Field D. Causality and the Kramers-Kronig Relations THE MICROSCOPIC THEORY EXPERIMENTAL METHODS SOME ILLUSTRATIVE EXAMPLES OF SUBMILLIMETER Dielectric MEASUREMENTS A. Polar Liquids B. Nonpolar Liquids C. Solutions of Polar Molecules in Nonpolar Solvents D. Polymers E. Plastic Crystals F. Glasses REFERENCES 1 5 5 9 15 16 21 26 30 30 31 35 38 45 46 47 I. Introduction The study of liquids and polymers by means of far-infrared and submilli-meter spectroscopy forms part of the much larger topic of Dielectric physics. A Dielectric medium is one in which there are no free charges so the dc conductivity is zero, but the medium can sustain displacement currents and these may have lossy components. Thus Dielectrics are all materials that are not metallic, semiconducting, or ionized. If an external field E is applied to a Dielectric, the field inside the Dielectric is given by D = (e/e 0 )E, (1) where ε is the permittivity of the Dielectric and ε 0 the absolute permittivity of free space (8.85418 X 10 12 F/m). In nearly all Dielectric work, however, it is customary to write ε = ε/ε 0 to avoid the constant apperance of the ε 0 factor; then ε so defined is the relative permittivity of the medium, i.e., the permit-1 Copyright © 1983 by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN 0-12-147708-8 2 G. W. CHANTRY tivity relative to that of the vacuum. The relative permittivity is complex because it will have a lossy component, and one therefore usually writes g = β ' -/ β , (2) where the caret is used to signify an explicitly complex quantity.

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  Color Imaging

  Fundamentals and Applications

  • Erik Reinhard, Erum Arif Khan, Ahmet Oguz Akyuz, Garrett Johnson(Authors)
  • 2008(Publication Date)
  • A K Peters/CRC Press

    (Publisher)

  In the presence of an electromagnetic field, electrons remain bound, but may be displaced. In such cases, the electrons may be thought of as orbiting around a point that is some 3.6. Polarization in Dielectric Materials 183 distance away from the nucleus. As a result, the negative charge of the electrons is slightly offset with respect to the positive charge of the nucleus. An atom under the influence of an electromagnetic field may thus form an electric dipole . The atom is said to be polarized under these conditions. Some Dielectrics are known as polar substances, where the molecular struc-ture is such that dipoles exist even in the absence of an external electromagnetic field. This is for instance the case with water. However, for polar substances, the orientation of each molecule is random, and therefore the net polarization of the material in bulk is zero. When an electric field is applied, the forces acting upon the molecules will align them with the field, and the material will become polarized. This phenomenon is called orientational polarization . Some materials consist of ions that are bound together. As an example, sodium chloride NaCl consists of positive and negative ions. Application of an external electric field will separate the ions and thus form electric dipoles. The result is called ionic polarization . A polarized atom may be modeled as a positive point charge + Q and a neg-ative point charge − Q separated by a distance r . The dipole moment p is then defined as p = Q r . (3.78) It would be difficult to model the interaction of an electromagnetic wave with a material if the dipole moments of each individual atom or molecule need to be considered. It is more convenient to compute the average behavior of the material at the microscopic scale.

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