Dielectric inorganics glass

Since the relative dielectric constant of inorganic glasses is low, typically between 5 and 15, ionic species are strongly associated. For instance most of the Ag cations will be associated with non-bridging oxygens in AgPOj glass. Nevertheless, thermal vibrations allow a partial... 

T. Nakajima [1972] Correlations Between Electrical Conduction and Dielectric Polarization in Inorganic Glasses, in 1971 Annual Report, Conference on Electrical Insulation and Dielectric Phenomena (National Academy of Sciences, Washington, DC), 168-176. 

The important feature of LC polyesters is a low coeffident of thermal expansion a < 1 x 10 grad that is comparable with the value for inorganic glasses (5 x 10 grad ) and significantly less in comparison with ordinary polymers (1 x 10 grad" ). These properties have led to the use of Vectra LC polymers in many electronic applications such as sockets, switches, bobbins, connectors, chip carriers, and sensors. Vectra LC polymers have replaced stainless steel in medical applications. The LC polyesters are particularly attractive for miaowave frequency electronics due to low relative dielectric constants, low dissipation factors, and the commerdal availability of laminates. 

Similar, very detailed studies were made by Ebert [112] on water adsorbed on alumina with similar conclusions. Water adsorbed on zeolites showed a dielectric constant of only 14-21, indicating greatly reduced mobility of the water dipoles [113]. Similar results were found for ammonia adsorbed in Vycor glass [114]. Klier and Zettlemoyer [114a] have reviewed a number of aspects of the molecular structure and dynamics of water at the surface of an inorganic material. 

Aromatic polyimides have glass transition temperatures in excess of 400 °C, excellent toughness and elongation properties and dielectric constants comparable to that of inorganic dielectrics, about 3.5. An important feature relative to these applications is their ability to planarize the topography when spun on as the soluble precursor polyamic acid. The subsequent intramolecular condensation reaction to form the heterocyclic imide is typically a thermal "curing" process. 

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