Organic insulating materials densities

Electronic conduction in insulating materials has been a subject of considerable interest in the quest to understand charge transport in the thin film layers of organic electronic devices. In typical dielectric materials, the electronic states near the Fermi level are usually localized states, and the electron wave functions decay exponentially over a distance known as the localization length. In constrast, metals have a high, generally uniform density of states, whereas semiconductors have well-separated conduction and valence bands (separated... 

Refractory Fibers Recently, zirconia-based insulating material with a low density and a low thermal conductivity has been developed in the form of fibers, paper, felt, board and shaped articles. The material is a cubic zirconia soHd solution stabilized with yttria, and has a maximum usable temperature of >2100 C. The innovative fabrication technique involves the use of an organic precursor fiber as a structural template, impregnated with an aqueous solution of zirconium chloride and yttrium chloride. The metallic salts are deposited within the organic fiber, which can subsequently be burned off by a controlled oxidation. The hollow remainder is then fired at a sufficiently high temperature (800-1300 °C) so as to induce crystallization, after which the oxide particles are sintered to develop a ceramic bond. Other techniques to produce refractory fibers involve phase inver-... 

The electronic properties of organic conductors are discussed by physicists in terms of band structure and Fermi surface. The shape of the band structure is defined by the dispersion energy and characterizes the electronic properties of the material (semiconductor, semimetals, metals, etc.) the Fermi surface is the limit between empty and occupied electronic states, and its shape (open, closed, nested, etc.) characterizes the dimensionality of the electron gas. From band dispersion and filling one can easily deduce whether the studied material is a metal, a semiconductor, or an insulator (occurrence of a gap at the Fermi energy). The intra- and interchain band-widths can be estimated, for example, from normal-incidence polarized reflectance, and the densities of state at the Fermi level can be used in the modeling of physical observations. The Fermi surface topology is of importance to predict or explain the existence of instabilities of the electronic gas (nesting vector concept see Chapter 2 of this book). Fermi surfaces calculated from structural data can be compared to those observed by means of the Shubnikov-de Hass method in the case of two- or three-dimensional metals [152]. 

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