Electrical conductivity of glass

Myuller R. L., Electrical Conductivity of Glass-Forming Substances (in Russian), Izdat. Leningr. Universiteta, Leningrad, 1968... 

Electrical conductivity of glasses and their melts, especially from the point of view of the mechanisms involved, is dealt with in detail by Mjuller (1968), Doremus (1973) and others. 

Good examples of small polaron transport are the glasses containing transition metal ions in two valence states such as (V, V ), (Fe, Fe ), (Cu, Cu ) and (Mo ", Mo ). In all of them, when the electron jumps from the lower valent ion to the higher valent ion, the lattice distortion also moves along with the electron. Mott derived an expression for the polaronic d.c. electrical conductivity of glasses containing transition metal ions. 

The formation of a glass in the arsenic-selenium-copper system is facilitated by the formation of three-dimensional structural units that contain all three components. The structural units formed in the glass evidently have a similar composition and structure to the well-known ternary compound Cu3AsSe4. The increase in the electrical conductivity of the arsenic selenides brought about by the introduction of copper is due to the accumulation of these structural units in the ass. The temperature dependence of the electrical conductivity of glasses with a hi copper content is similar to that of polycrystalline CusAsSei. 

Electrical conduction ia glasses is mainly attributed to the migration of mobile ions such as LE, Na", K", and OH under the influence of an appHed field. At higher temperatures, >250° C, divalent ions, eg, Ca " and Mg ", contribute to conduction, although their mobiUty is much less (14). Conduction ia glass is an activated process and thus the number of conducting ions iacreases with both temperature and field. The temperature—resistivity dependence is given... 

The chemical reactions of IF5 have been more extensively and systematically studied because the compound can be handled in glass apparatus and is much less vigorous a reagent than the other pentafluorides. The (very low) electrical conductivity of the pure liquid has been ascribed to slight ionic dissociation according to the equilibrium... 

These methods are based on the electrical conductivity of a low volume fraction of CNTs in the matrix and are therefore more suitable for non-conductive fibers (glass, polymeric). In hierarchical CF composites, electrical conduction is dominated by the properties of the macroscopic fibers present at much higher volume fraction, which cannot be decoupled from those of the nanocarbons. 

Estimation of the diffusion coefficient from the data on the electrical conductivity of nitrate glasses has shown that, in the KN03 + Ca(N03)2 matrix, the diffusional decay of N03 radicals at T < 297 K and t < 102s is negligible. A rise of temperature in the low-temperature region results in a small increase in the slope of kinetic curves. Thus, just as in the case of the decay of N03 in the water-alkaline matrix, the decay of N03 radicals in the KN03 + Ca(N03)2 matrix at low temperatures is an activated electron tunneling process. 

A device for foam dispersity determination by measuring the local foam expansion ratio and the pressure in Plateau borders is illustrated in Fig. 4.4. It consists of a glass container equipped with platinum electrodes and a micromanometer. The container bottom is a porous plate (a sintered glass filter). The pressure Ap is measured with a capillary micromanometer and the expansion ratio is determined by the electrical conductivity of the foam. The manometer and the electrodes are positioned so that to ensure a distance of 1.0-1.5 cm between them and the porous plate. When the distance is small the liquid in the porous... 

It is experimentally proved that the electrical resistance of the porous plates is negligible compared to that of the foam column. In order to estimate the resistance of the porous plates, instead of glass cup 2, a similar cup made of aluminum is used. During the experiment the porous plate soldered to the lid is in contact with both the foam and the aluminum cup. The electrical conductivity of the latter cup is 106 times higher than that of the... 

Special cells have been constructed for the study of the optical properties of foams [75], They allow a simultaneous determination of the foam optical density, the pressure in Plateau borders and the electrical conductivity of the foam. Furthermore, the foam produced by these cells is homogeneous with respect to all structural parameters (border radius and bubble size). The homogeneity of the foam formed is achieve by glass filters which provide foam drying and control on the formation of air spaces. 

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