From 09/16/2014 through 10/11/2012
1. “A dielectric 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 a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization. Because of dielectric polarization, positive charges are displaced toward the field and negative charges shift in the opposite direction. This creates an internal electric field which 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 axis aligns to the field.
Although the term "insulator" implies low electrical conduction, "dielectric" is typically used to describe materials with a high polarizability. The latter is expressed by a number called the dielectric constant.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, yet notable, 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.
The study of dielectric properties is concerned with the storage and dissipation of electric and magnetic energy in materials. It is important to explain various phenomena in electronics, optics, and solid-state physics.
The term "dielectric" was coined by William Whewell (from "dia-electric") in response to a request from Michael Faraday.
(Wikipedia, Dielectric Materials, 10/11/2012)
2. Low k dielectrics are conventionally defined as those materials that have a dielectric constant lower than that of silicon dioxide, that is k<.about.4. Typical methods of obtaining low-k materials include doping silicon dioxide with various hydrocarbons or fluorine. These doping methods, however, generally cannot produce materials with dielectric constants lower than about 2.6. With more and more advanced technology needs, present efforts are focused on developing low-k dielectric materials with k less than 2.5. These ultra low-k (ULK) dielectrics can be obtained by incorporating air voids within a low-k dielectric, creating a porous dielectric material. [Smargiassi et al, US Patent 8,282,768 (10/9/2012)]
Dielectric materials are commonly used in energy
storage devices, e.g., to separate opposing electrodes in an electrostatic
capacitor. Nanocomposite dielectric materials include inorganic nanoparticles
in a polymer base, which together have high dielectric constants due in part to
the inorganic nanoparticles while retaining much of the processibility of the
base polymer. There are still problems such as inadequate breakdown strength,
creating local hot spots. Miller and Duerksen avoided this problem using
mixtures of small (5 to 10 nm) and large nanoparticles (75 nm and more). The
smaller particles increase breakdown strength and the larger particles increase
the dielectric constant. The example consisted of polyvinylidene difluoride
containing 5 to 10 nm silica particles and 75 nm barium titanate particles.
US Patent 8,785,521 (July 22, 2014), “Two-Particle Nanocomposite Dielectrics,” Seth Adrian Miller, and Gary Lynn Duerksen (Empire Technology Development, LLC., Wilmington, Delaware, USA).
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Roger D. Corneliussen
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Copyright 2012 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is10/11/2012.