Dielectric - wikipedia Dielectric Not to be confused with Dielectric constant or Dialectic. A polarized dielectric material A dielectric ( or dielectric material ) is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor but only slightly shift from their average equilibrium positions causing dielectric polarization. Because of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the opposite direction. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axes align to the field. The study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. Dielectrics are important for explaining various phenomena in electronics, optics, solid - state physics, and cell biophysics. Contents 1 Terminology 2 Electric susceptibility 2.1 Dispersion and causality 3 Dielectric polarization 3.1 Ionic polarization 3.1. 1 In cells 4 Dielectric dispersion 5 Dielectric relaxation 5.1 Debye relaxation 5.2 Variants of the Debye equation 6 Paraelectricity 7 Tunability 8 Applications 8.1 Capacitors 8.2 Dielectric resonator 8.3 BST thin films 9 Some practical dielectrics 10 See also 11 References 12 Further reading 13 External links Terminology Although the term insulator implies low electrical conduction, dielectric typically means materials with a high polarizability. The latter is expressed by a number called the relative permittivity. The term insulator is generally used to indicate electrical obstruction while the term dielectric is used to indicate the energy storing capacity of the material ( by means of polarization ). A common example of a dielectric is the electrically insulating material between the metallic plates of a capacitor. The polarization of the dielectric by the applied electric field increases the capacitor 's surface charge for the given electric field strength. The term dielectric was coined by William Whewell ( from dia - + electric ) in response to a request from Michael Faraday. A perfect dielectric is a material with zero electrical conductivity ( cf. perfect conductor ), thus exhibiting only a displacement current ; therefore it stores and returns electrical energy as if it were an ideal capacitor. Electric susceptibility Main articles : Electric susceptibility and Permittivity The electric susceptibility χ of a dielectric material is a measure of how easily it polarizes in response to an electric field. This, in turn, determines the electric permittivity of the material and thus influences many other phenomena in that medium, from the capacitance of capacitors to the speed of light. It is defined as the constant of proportionality ( which may be a tensor ) relating an electric field E to the induced dielectric polarization density P such that P = ε 0 χ e E, ( displaystyle mathbf ( P ) = \varepsilon _ ( 0 ) chi _ ( e ) mathbf ( E ), ) where ε is the electric permittivity of free space. The susceptibility of a medium is related to its relative permittivity ε by χ e = ε r − 1. ( displaystyle chi _ ( e ) = \varepsilon _ ( r ) - 1. ) So in the case of a vacuum, χ e = 0. ( displaystyle chi _ ( e ) = 0. ) The electric displacement D is related to the polarization density P by D = ε 0 E + P = ε 0 ( 1 + χ e ) E = ε 0 ε r E. ( displaystyle mathbf ( D ) =\varepsilon _ ( 0 ) mathbf ( E ) + mathbf ( P ) =\varepsilon _ ( 0 ) left ( 1 + chi _ ( e ) \right ) mathbf ( E ) =\varepsilon _ ( 0 ) \varepsilon _ ( r ) mathbf ( E ). ) Dispersion and causality In general, a material can not polarize instantaneously in response to an applied field. The more general formulation as a function of time is P ( t ) = ε 0 ∫ − ∞ t χ e ( t − t ′ ) E ( t ′ ) d t ′. ( displaystyle mathbf ( P ) ( t ) = \varepsilon _ ( 0 ) int _ ( - infty ) ^ ( t ) chi _ ( e ) left ( t-t ' \right ) mathbf ( E ) left ( t ' \right ) , dt '. ) That is, the polarization is a convolution of the electric field at previous times with time - dependent susceptibility given by χ ( Δt ). The upper limit of this integral can be extended to infinity as well if one defines χ ( Δt ) = 0 for Δt < 0. An instantaneous response corresponds to Dirac delta function susceptibility χ ( Δt ) = χ δ ( Δt ). It is more convenient in a linear system to take the Fourier transform and write this relationship as a function of frequency. Due to the convolution theorem, the integral becomes a simple product, P ( ω ) = ε 0 χ e ( ω ) E ( ω ). ( displaystyle mathbf ( P ) ( omega ) = \varepsilon _ ( 0 ) chi _ ( e ) ( omega ) mathbf ( E ) ( omega ). ) Note the simple frequency dependence of the susceptibility, or equivalently the permittivity. The shape of the susceptibility with respect to frequency characterizes the dispersion properties of the material. Moreover, the fact that the polarization can only depend on the electric field at previous times ( i.e., χ ( Δt ) = 0 for Δt < 0 ), a consequence of causality, imposes Kramers -- Kronig constraints on the real and imaginary parts of the susceptibility χ ( ω ). Dielectric polarization Dipolar polarization is a polarization that is either inherent to polar molecules ( orientation polarization ), or can be induced in any molecule in which the asymmetric distortion of the nuclei is possible ( distortion polarization ). Orientation polarization results from a permanent dipole, e.g., that arising from the 104.45 ° angle between the asymmetric bonds between oxygen and hydrogen atoms in the water molecule, which retains polarization in the absence of an external electric field. The assembly of these dipoles forms a macroscopic polarization. When an external electric field is applied, the distance between charges within each permanent dipole, which is related to chemical bonding, remains constant in orientation polarization ; however, the direction of polarization itself rotates. This rotation occurs on a timescale that depends on the torque and surrounding local viscosity of the molecules. Because the rotation is not instantaneous, dipolar polarizations lose the response to electric fields at the highest frequencies. A molecule rotates about 1 radian per picosecond in a fluid, thus this loss occurs at about 10 Hz ( in the microwave region ). The delay of the response to the change of the electric field causes friction and heat. When an external electric field is applied at infrared frequencies or less, the molecules are bent and stretched by the field and the molecular dipole moment changes. The molecular vibration frequency is roughly the inverse of the time it takes for the molecules to bend, and this distortion polarization disappears above the infrared. Ionic polarization Ionic polarization is polarization caused by relative displacements between positive and negative ions in ionic crystals ( for example, NaCl ). If a crystal or molecule consists of atoms of more than one kind, the distribution of charges around an atom in the crystal or molecule leans to positive or negative. As a result, when lattice vibrations or molecular vibrations induce relative displacements of the atoms, the centers of positive and negative charges are also displaced. The locations of these centers are affected by the symmetry of the displacements. When the centers do n't correspond, polarization arises in molecules or crystals. This polarization is called ionic polarization. Ionic polarization causes the ferroelectric effect as well as dipolar polarization. The ferroelectric transition, which is caused by the lining up of the orientations of permanent dipoles along a particular direction, is called an order - disorder phase transition. The transition caused by ionic polarizations in crystals is called a displacive phase transition. In cells Ionic polarization enables the production of energy - rich compounds in cells ( the proton pump in mitochondria ) and, at the plasma membrane, the establishment of the resting potential, energetically unfavourable transport of ions, and cell - to - cell communication ( the Na+ / K+ - ATPase ). All cells in animal body tissues are electrically polarized -- in other words, they maintain a voltage difference across the cell 's plasma membrane, known as the membrane potential. This electrical polarization results from a complex interplay between ion transporters and ion channels. In neurons, the types of ion channels in the membrane usually vary across different parts of the cell, giving the dendrites, axon, and cell body different electrical properties. As a result, some parts of the membrane of a neuron may be excitable ( capable of generating action potentials ), whereas others are not. Dielectric dispersion In physics, dielectric dispersion is the dependence of the permittivity of a dielectric material on the frequency of an applied electric field. Because there is a lag between changes in polarization and changes in the electric field, the permittivity of the dielectric is a complicated function of frequency of the electric field. Dielectric dispersion is very important for the applications of dielectric materials and for the analysis of polarization systems. This is one instance of a general phenomenon known as material dispersion : a frequency - dependent response of a medium for wave propagation. When the frequency becomes higher : dipolar polarization can no longer follow the oscillations of the electric field in the microwave region around 10 Hz ; ionic polarization and molecular distortion polarization can no longer track the electric field past the infrared or far - infrared region around 10 Hz, ; electronic polarization loses its response in the ultraviolet region around 10 Hz. In the frequency region above ultraviolet, permittivity approaches the constant ε in every substance, where ε is the permittivity of the free space. Because permittivity indicates the strength of the relation between an electric field and polarization, if a polarization process loses its response, permittivity decreases. Dielectric relaxation Dielectric relaxation is the momentary delay ( or lag ) in the dielectric constant of a material. This is usually caused by the delay in molecular polarization with respect to a changing electric field in a dielectric medium ( e.g., inside capacitors or between two large conducting surfaces ). Dielectric relaxation in changing electric fields could be considered analogous to hysteresis in changing magnetic fields ( for inductors or transformers ). Relaxation in general is a delay or lag in the response of a linear system, and therefore dielectric relaxation is measured relative to the expected linear steady state ( equilibrium ) dielectric values. The time lag between electrical field and polarization implies an irreversible degradation of Gibbs free energy. In physics, dielectric relaxation refers to the relaxation response of a dielectric medium to an external, oscillating electric field. This relaxation is often described in terms of permittivity as a function of frequency, which can, for ideal systems, be described by the Debye equation. On the other hand, the distortion related to ionic and electronic polarization shows behavior of the resonance or oscillator type. The character of the distortion process depends on the structure, composition, and surroundings of the sample. Debye relaxation Debye relaxation is the dielectric relaxation response of an ideal, noninteracting population of dipoles to an alternating external electric field. It is usually expressed in the complex permittivity ε of a medium as a function of the field 's frequency ω : ε ^ ( ω ) = ε ∞ + Δ ε 1 + i ω τ, ( displaystyle ( hat ( \varepsilon ) ) ( omega ) = \varepsilon _ ( infty ) + ( \frac ( Delta \varepsilon ) ( 1 + i omega \tau ) ), ) where ε is the permittivity at the high frequency limit, Δε = ε − ε where ε is the static, low frequency permittivity, and τ is the characteristic relaxation time of the medium. Separating the real and imaginary parts of the complex dielectric permittivity yields : ε ′ = ε ∞ + ε s − ε ∞ 1 + ω 2 τ 2 ε '' = ( ε s − ε ∞ ) ω τ 1 + ω 2 τ 2 ( displaystyle ( \begin ( aligned ) \varepsilon ' & = \varepsilon _ ( infty ) + ( \frac ( \varepsilon _ ( s ) - \varepsilon _ ( infty ) ) ( 1 + omega ^ ( 2 ) \tau ^ ( 2 ) ) ) ( 3pt ) \varepsilon ' ' & = ( \frac ( ( \varepsilon _ ( s ) - \varepsilon _ ( infty ) ) omega \tau ) ( 1 + omega ^ ( 2 ) \tau ^ ( 2 ) ) ) end ( aligned ) ) ) The dielectric loss is also represented by : tan ⁡ ( δ ) = ε '' ε ′ = ( ε s − ε ∞ ) ω τ ε s + ε ∞ ω 2 τ 2 ( displaystyle \tan ( delta ) = ( \frac ( \varepsilon ' ' ) ( \varepsilon ' ) ) = ( \frac ( left ( \varepsilon _ ( s ) - \varepsilon _ ( infty ) \right ) omega \tau ) ( \varepsilon _ ( s ) + \varepsilon _ ( infty ) omega ^ ( 2 ) \tau ^ ( 2 ) ) ) ) This relaxation model was introduced by and named after the physicist Peter Debye ( 1913 ). It is characteristic for dynamic polarization with only one relaxation time. Variants of the Debye equation Cole -- Cole equation This equation is used when the dielectric loss peak shows symmetric broadening. Cole -- Davidson equation This equation is used when the dielectric loss peak shows asymmetric broadening. Havriliak -- Negami relaxation This equation considers both symmetric and asymmetric broadening. Kohlrausch -- Williams -- Watts function Fourier transform of stretched exponential function. Curie -- von Schweidler law This shows the response of dielectrics to an applied DC field to behave according to a power law, which can be expressed as an integral over weighted exponential functions. Paraelectricity See also : Ferroelectricity Paraelectricity is the ability of many materials ( specifically ceramics ) to become polarized under an applied electric field. Unlike ferroelectricity, this can happen even if there is no permanent electric dipole that exists in the material, and removal of the fields results in the polarization in the material returning to zero. The mechanisms that cause paraelectric behaviour are the distortion of individual ions ( displacement of the electron cloud from the nucleus ) and polarization of molecules or combinations of ions or defects. Paraelectricity can occur in crystal phases where electric dipoles are unaligned and thus have the potential to align in an external electric field and weaken it. An example of a paraelectric material of high dielectric constant is strontium titanate. The LiNbO crystal is ferroelectric below 1430 K, and above this temperature it transforms into a disordered paraelectric phase. Similarly, other perovskites also exhibit paraelectricity at high temperatures. Paraelectricity has been explored as a possible refrigeration mechanism ; polarizing a paraelectric by applying an electric field under adiabatic process conditions raises the temperature, while removing the field lowers the temperature. A heat pump that operates by polarizing the paraelectric, allowing it to return to ambient temperature ( by dissipating the extra heat ), bringing it into contact with the object to be cooled, and finally depolarizing it, would result in refrigeration. Tunability Tunable dielectrics are insulators whose ability to store electrical charge changes when a voltage is applied. Generally, strontium titanate ( SrTiO ) is used for devices operating at low temperatures, while barium strontium titanate ( Ba Sr TiO ) substitutes for room temperature devices. Other potential materials include microwave dielectrics and carbon nanotube ( CNT ) composites. In 2013 multi-sheet layers of strontium titanate interleaved with single layers of strontium oxide produced a dielectric capable of operating at up to 125 GHz. The material was created via molecular beam epitaxy. The two have mismatched crystal spacing that produces strain within the strontium titanate layer that makes it less stable and tunable. Systems such as Ba Sr TiO have a paraelectric -- ferroelectric transition just below ambient temperature, providing high tunability. Such films suffer significant losses arising from defects. Applications Capacitors Main article : Capacitor Charge separation in a parallel - plate capacitor causes an internal electric field. A dielectric ( orange ) reduces the field and increases the capacitance. Commercially manufactured capacitors typically use a solid dielectric material with high permittivity as the intervening medium between the stored positive and negative charges. This material is often referred to in technical contexts as the capacitor dielectric. The most obvious advantage to using such a dielectric material is that it prevents the conducting plates, on which the charges are stored, from coming into direct electrical contact. More significantly, however, a high permittivity allows a greater stored charge at a given voltage. This can be seen by treating the case of a linear dielectric with permittivity ε and thickness d between two conducting plates with uniform charge density σ. In this case the charge density is given by σ ε = ε V d ( displaystyle sigma _ ( \varepsilon ) = \varepsilon ( \frac ( V ) ( d ) ) ) and the capacitance per unit area by c = σ ε V = ε d ( displaystyle c = ( \frac ( sigma _ ( \varepsilon ) ) ( V ) ) = ( \frac ( \varepsilon ) ( d ) ) ) From this, it can easily be seen that a larger ε leads to greater charge stored and thus greater capacitance. Dielectric materials used for capacitors are also chosen such that they are resistant to ionization. This allows the capacitor to operate at higher voltages before the insulating dielectric ionizes and begins to allow undesirable current. Dielectric resonator Main article : Dielectric resonator A dielectric resonator oscillator ( DRO ) is an electronic component that exhibits resonance of the polarization response for a narrow range of frequencies, generally in the microwave band. It consists of a `` puck '' of ceramic that has a large dielectric constant and a low dissipation factor. Such resonators are often used to provide a frequency reference in an oscillator circuit. An unshielded dielectric resonator can be used as a dielectric resonator antenna ( DRA ). BST thin films From 2002 to 2004, the Army Research Laboratory ( ARL ) conducted research on thin film technology. Barium strontium titanate ( BST ), a ferroelectric thin film, was studied for the fabrication of radio frequency and microwave components, such as voltage - controlled oscillators, tunable filters, and phase shifters. The research was part of an effort to provide the Army with highly - tunable, microwave - compatible materials for broadband electric - field tunable devices, which operate consistently in extreme temperatures. This work improved tunability of bulk barium strontium titanate, which is a thin film enabler for electronics components. In a 2004 research paper, ARL researchers explored how small concentrations of acceptor dopants can dramatically modify the properties of ferroelectric materials such as BST. Researchers `` doped '' BST thin films with magnesium, analyzing the `` structure, microstructure, surface morphology and film / substrate compositional quality '' of the result. The Mg doped BST films showed `` improved dielectric properties, low leakage current, and good tunability, '' meriting potential for use in microwave tunable devices. Some practical dielectrics Dielectric materials can be solids, liquids, or gases. In addition, a high vacuum can also be a useful, nearly lossless dielectric even though its relative dielectric constant is only unity. Solid dielectrics are perhaps the most commonly used dielectrics in electrical engineering, and many solids are very good insulators. Some examples include porcelain, glass, and most plastics. Air, nitrogen and sulfur hexafluoride are the three most commonly used gaseous dielectrics. Industrial coatings such as parylene provide a dielectric barrier between the substrate and its environment. Mineral oil is used extensively inside electrical transformers as a fluid dielectric and to assist in cooling. Dielectric fluids with higher dielectric constants, such as electrical grade castor oil, are often used in high voltage capacitors to help prevent corona discharge and increase capacitance. Because dielectrics resist the flow of electricity, the surface of a dielectric may retain stranded excess electrical charges. This may occur accidentally when the dielectric is rubbed ( the triboelectric effect ). This can be useful, as in a Van de Graaff generator or electrophorus, or it can be potentially destructive as in the case of electrostatic discharge. Specially processed dielectrics, called electrets ( which should not be confused with ferroelectrics ), may retain excess internal charge or `` frozen in '' polarization. Electrets have a semipermanent electric field, and are the electrostatic equivalent to magnets. Electrets have numerous practical applications in the home and industry. Some dielectrics can generate a potential difference when subjected to mechanical stress, or ( equivalently ) change physical shape if an external voltage is applied across the material. This property is called piezoelectricity. Piezoelectric materials are another class of very useful dielectrics. Some ionic crystals and polymer dielectrics exhibit a spontaneous dipole moment, which can be reversed by an externally applied electric field. This behavior is called the ferroelectric effect. These materials are analogous to the way ferromagnetic materials behave within an externally applied magnetic field. Ferroelectric materials often have very high dielectric constants, making them quite useful for capacitors. See also Classification of materials based on permittivity Paramagnetism Clausius - Mossotti relation Dielectric absorption Dielectric losses Dielectric strength Dielectric spectroscopy EIA Class 1 dielectric EIA Class 2 dielectric High - k dielectric Low - k dielectric leakage Linear response function Metamaterial RC delay Rotational Brownian motion Paschen 's law -- variation of Dielectric strength of gas related to pressure References ^ Jump up to : Dielectric. Encyclopædia Britannica : `` Dielectric, insulating material or a very poor conductor of electric current. When dielectrics are placed in an electric field, practically no current flows in them because, unlike metals, they have no loosely bound, or free, electrons that may drift through the material. '' Jump up ^ Arthur R. von Hippel, in his seminal work, Dielectric Materials and Applications, stated : `` Dielectrics... are not a narrow class of so - called insulators, but the broad expanse of nonmetals considered from the standpoint of their interaction with electric, magnetic, or electromagnetic fields. Thus we are concerned with gases as well as with liquids and solids, and with the storage of electric and magnetic energy as well as its dissipation. '' ( Technology Press of MIT and John Wiley, NY, 1954 ). Jump up ^ Thoms, E. ; Sippel, P. ; et., al. ( 2017 ). `` Dielectric study on mixtures of ionic liquids ''. Sci. Rep. arXiv : 1703.05625. Bibcode : 2017NatSR... 7.7463 T. doi : 10.1038 / s41598 - 017 - 07982 - 3. Jump up ^ Belkin, A. ; Bezryadin, A. ; Hendren, L. ; Hubler, A. ( 2017 ). `` Recovery of Alumina Nanocapacitors after High Voltage Breakdown ''. Sci. Rep. Bibcode : 2017NatSR... 7... 932B. doi : 10.1038 / s41598 - 017 - 01007 - 9. Jump up ^ Daintith, J. ( 1994 ). Biographical Encyclopedia of Scientists. CRC Press. p. 943. ISBN 0 - 7503 - 0287 - 9. Jump up ^ James, Frank A.J.L., editor. The Correspondence of Michael Faraday, Volume 3, 1841 -- 1848, `` Letter 1798, William Whewell to Faraday, p. 442 ''. The Institution of Electrical Engineers, London, United Kingdom, 1996. ISBN 0 - 86341 - 250 - 5 Jump up ^ Microwave Engineering -- R.S. Rao ( Prof. ). Retrieved 2013 - 11 - 08. Jump up ^ Kao, Kwan Chi ( 2004 ). Dielectric Phenomena in Solids. London : Elsevier Academic Press. pp. 92 -- 93. ISBN 0 - 12 - 396561 - 6. Jump up ^ Debye, P. ( 1913 ), Ver. Deut. Phys. Gesell. 15, 777 ; reprinted 1954 in collected papers of Peter J.W. Debye. Interscience, New York Jump up ^ Chiang, Y. et al. ( 1997 ) Physical Ceramics, John Wiley & Sons, New York Jump up ^ Kuhn, U. ; Lüty, F. ( 1965 ). `` Paraelectric heating and cooling with OH -- dipoles in alkali halides ''. Solid State Communications. 3 ( 2 ) : 31. Bibcode : 1965SSCom... 3... 31K. doi : 10.1016 / 0038 - 1098 ( 65 ) 90060 - 8. ^ Jump up to : Lee, Che - Hui ; Orloff, Nathan D. ; Birol, Turan ; Zhu, Ye ; Goian, Veronica ; Rocas, Eduard ; Haislmaier, Ryan ; Vlahos, Eftihia ; Mundy, Julia A. ; Kourkoutis, Lena F. ; Nie, Yuefeng ; Biegalski, Michael D. ; Zhang, Jingshu ; Bernhagen, Margitta ; Benedek, Nicole A. ; Kim, Yongsam ; Brock, Joel D. ; Uecker, Reinhard ; Xi, X.X. ; Gopalan, Venkatraman ; Nuzhnyy, Dmitry ; Kamba, Stanislav ; Muller, David A. ; Takeuchi, Ichiro ; Booth, James C. ; Fennie, Craig J. ; Schlom, Darrell G. ( 2013 ). `` Self - correcting crystal may lead to the next generation of advanced communications ''. Nature. 502 ( 7472 ) : 532. Bibcode : 2013Natur. 502... 532L. doi : 10.1038 / nature12582. PMID 24132232. Jump up ^ Lee, C.H. ; Orloff, N.D. ; Birol, T. ; Zhu, Y. ; Goian, V. ; Rocas, E. ; Haislmaier, R. ; Vlahos, E. ; Mundy, J.A. ; Kourkoutis, L.F. ; Nie, Y. ; Biegalski, M.D. ; Zhang, J. ; Bernhagen, M. ; Benedek, N.A. ; Kim, Y. ; Brock, J.D. ; Uecker, R. ; Xi, X.X. ; Gopalan, V. ; Nuzhnyy, D. ; Kamba, S. ; Muller, D.A. ; Takeuchi, I. ; Booth, J.C. ; Fennie, C.J. ; Schlom, D.G. ( 2013 ). `` Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics ''. Nature. 502 ( 7472 ) : 532 -- 536. Bibcode : 2013Natur. 502... 532L. doi : 10.1038 / nature12582. hdl : 2117 / 21213. PMID 24132232. Jump up ^ Kong, L.B. ; Li, S. ; Zhang, T.S. ; Zhai, J.W. ; Boey, F.Y.C. ; Ma, J. ( 2010 - 11 - 30 ). `` Electrically tunable dielectric materials and strategies to improve their performances ''. Progress in Materials Science. 55 ( 8 ) : 840 -- 893. doi : 10.1016 / j. pmatsci. 2010.04. 004. Jump up ^ Giere, A. ; Zheng, Y. ; Maune, H. ; Sazegar, M. ; Paul, F. ; Zhou, X. ; Binder, J.R. ; Muller, S. ; Jakoby, R. ( 2008 ). `` Tunable dielectrics for microwave applications ''. 2008 17th IEEE International Symposium on the Applications of Ferroelectrics. p. 1. doi : 10.1109 / ISAF. 2008.4693753. ISBN 978 - 1 - 4244 - 2744 - 4. Jump up ^ Müssig, Hans - Joachim. Semiconductor capacitor with praseodymium oxide as dielectric, U.S. Patent 7,113,388 published 2003 - 11 - 06, issued 2004 - 10 - 18, assigned to IHP GmbH - Innovations for High Performance Microelectronics / Institute Fur Innovative Mikroelektronik ^ Jump up to : `` Novel tunable acceptor doped BST thin films for high quality tunable microwave devices ''. REVISTA MEXICANA DE FI  ́ SICA. Jump up ^ Nair, K.M. ; Guo, Ruyan ; Bhalla, Amar S. ; Hirano, S. - I. ; Suvorov, D. ( 2012 - 04 - 11 ). Developments in Dielectric Materials and Electronic Devices : Proceedings of the 106th Annual Meeting of The American Ceramic Society, Indianapolis, Indiana, USA 2004. John Wiley & Sons. ISBN 9781118408193. Jump up ^ Nair, K.M. ; Bhalla, Amar S. ; Hirano, S. - I. ; Suvorov, D. ; Schwartz, Robert W. ; Zhu, Wei ( 2012 - 04 - 11 ). Ceramic Materials and Multilayer Electronic Devices. John Wiley & Sons. ISBN 9781118406762. Jump up ^ Cole, M.W. ; Hubbard, C. ; Ngo, E. ; Ervin, M. ; Wood, M. ; Geyer, R.G. ( 2002 - 07 ). `` Structure -- property relationships in pure and acceptor - doped Ba1 − xSrxTiO3 thin films for tunable microwave device applications ''. Journal of Applied Physics. 92 ( 1 ) : 475 -- 483. doi : 10.1063 / 1.1484231. ISSN 0021 - 8979. Check date values in : date = ( help ) Jump up ^ Lyon, David ( 2013 ). `` Gap size dependence of the dielectric strength in nano vacuum gaps ''. IEEE Transactions on Dielectrics and Electrical Insulation. 20 ( 4 ). doi : 10.1109 / TDEI. 2013.6571470. Further reading Jackson, John David ( August 10, 1998 ). Classical Electrodynamics ( 3 rd ed. ). John Wiley & Sons. ISBN 978 - 0 - 471 - 30932 - 1. 808 or 832 pages. Scaife, Brendan ( September 3, 1998 ). Principles of Dielectrics ( Monographs on the Physics & Chemistry of Materials ) ( 2 nd ed. ). Oxford University Press. ISBN 978 - 0198565574. External links Electromagnetism -- A chapter from an online textbook Dielectric Sphere in an Electric Field DoITPoMS Teaching and Learning Package `` Dielectric Materials '' Texts on Wikisource : `` Dielectric ''. Encyclopedia Americana. 1920. `` Dielectric ''. Encyclopædia Britannica ( 11th ed. ). 1911. Polarization states dielectric paraelectricity ferroelectricity antiferroelectricity helielectricity ferrielectricity GND : 4149716 - 8 NDL : 00574419 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Dielectric&oldid=856806496 '' Categories : Electric and magnetic fields in matter Dielectrics Hidden categories : CS1 errors : dates Wikipedia articles incorporating a citation from the Encyclopedia Americana with a Wikisource reference Wikipedia articles incorporating a citation from the 1911 Encyclopaedia Britannica with Wikisource reference Wikipedia articles with GND identifiers Wikipedia articles with NDL identifiers Talk Contents About Wikipedia Asturianu Azərbaycanca Беларуская Беларуская ( тарашкевіца ) ‎ Български Català Čeština Dansk Deutsch Eesti Ελληνικά Español Esperanto فارسی Français Gaeilge Galego 한국어 Հայերեն हिन्दी Hrvatski Ido Bahasa Indonesia Italiano עברית ქართული Қазақша Kreyòl ayisyen Latviešu Lietuvių Magyar Македонски മലയാളം Nederlands 日本 語 Norsk nynorsk Oʻzbekcha / ўзбекча Polski Português Русский Scots Slovenčina Slovenščina Suomi Svenska ไทย Türkçe Українська Tiếng Việt 中文 42 more Edit links This page was last edited on 27 August 2018, at 17 : 07 ( UTC ). 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Question: what is the purpose of a dielectric material used in a capacitor
Answer: insulator