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11.
Z. Ovadyahu 《Physica A》1993,200(1-4):462-468
The optical gap, Eg, of amorphous indium-oxide films is measured as a function of static disorder near the metal-insulator transition. On the insulating side of the transition the optical gap obeys a scaling relation, ΔEg = -E*Δg where E* is of the order of the Fermi energy of the given sample and g≡KFl. These results are ascribed to the continuous shift of the mobility-edge in the conduction band with disorder. 相似文献
12.
Montmorillonite and Laponite loaded with different amounts of tributylammonium cations (TBAH+), up to 40 and 30 mmol, respectively, per 100 g clay, were studied by thermo-XRD-analysis. TBAH-smectites heated at 300 and 420°C exhibited basal spacings of 1.30 and 1.24 nm, attributed to smectite tactoids with low- and high-temperature-stable monolayer charcoals, respectively in the interlayers. DTA-EGA and TG of the TBAH-smectites showed four stages of mass loss labeled A, B, C and D. Stage A below 250°C, accompanied by an endothermic DTA peak, resulted from the dehydration of the clay. Mass loss stages B, C and D, at 250–380, 380–605°C and above 605°C, respectively, accompanied by exothermic DTA peaks, were due to three oxidation steps of the organic matter. In mass loss stage B (first oxidation step) mainly organic hydrogen was oxidized to H2O whereas carbon and nitrogen formed low- and high-temperature-stable charcoals. In stages C and D (second and third oxidation steps) low- and high-temperature- stable charcoals were oxidized, respectively. Dehydroxylation of the smectites occurred together with the second and third oxidation steps. Thermal mass loss at each step was calculated from the TG curves showing that in montmorillonite the percentage of high-temperature-stable charcoal from total charcoal decreased with higher TBAH+ loadings of the clay whereas in Laponite this percentage increased with higher loadings of the clay. 相似文献
13.
The Hall coefficient of 3D, crystalline indium-oxide films has been measured as a function of temperature and disorder. It is found that the Hall coefficient remains virtually constant as the temperature is varied between 12 K and room temperature for samples with KFl values of 0.1 to ≈3.4. 相似文献
14.
We have measured the electrical resistivity of InGe, PbGe and A?Ge mixtures co-evaporated onto room temperature substrates, and studied their microstructure by transmission electron microscopy. In InGe and PbGe, where we have observed a random distribution of the constituents, the metal-insulator transition occurs at a metal concentration of about 15% vol., in agreement with random continuum percolation theory. In contrast, A?Ge has a highly regular granular structure and a much higher critical concentration (~ 55%), as do most metal-insulator thin film mixtures. 相似文献
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N. Lahav D. Ovadyahu A. Gutkin E. Mastov T. Menjeritzki A. Adin L. Rubinstein D. Tropp S. Yariv 《Journal of Thermal Analysis and Calorimetry》1994,42(1):67-84
A device was constructed in which a clay suspension is hermetically heated at 220°C for a few minutes. This thermal treatment
is accompanied by a pressure increase in the cell. Once the valve is opened, there is a fast release of the pressure inside
the cell and a sudden evolution of the interparticle water. This shock leads to a quasi explosion of the clay particle. This
technique was named thermal vapour pressure shock explosion (TSE). The effect of TSE treatment on the properties of palygorskite
suspensions was investigated. Palygorskite suspensions in water are rather unstable and particles smaller than 3 μm in size
are not found before a TSE treatment. Stabilization of the suspension can be obtained by TSE treatments and/or by using a
dispersing agent such as pyrophosphate, or both. As a result of TSE treatments smaller particles are obtained, the dispersiveness
of the particles is improved and electrophoretic mobility is increased. Electron microscopy scans showed that the aggregates
of needles which form the palygorskite fibres, disintegrate to separated thin needles as a result of the TSE treatment.
Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65th birthday 相似文献
18.
Aging, commonly observed in glasses, is a manifestation of breakdown of time-translational invariance. Here we demonstrate experimentally aging effects in the electronic system of an Anderson insulator. The aging phenomenon in the electron glass appears to be much less sensitive to temperature than in other systems. The differences in the behavior of the electron glass and a spin glass system are discussed in terms of some microscopic differences between the two systems. 相似文献
19.
Ovadyahu Z 《Physical review letters》2007,99(22):226603
It is experimentally shown that, depending on the carrier concentration of the system n, the dynamics of electron glasses either slows down with increasing temperature or it is independent of it. This also correlates with the dependence of a typical relaxation time (or "viscosity") on n. These linked features are argued to be consistent with a model for dissipative tunneling. The slow relaxation of the electron glass may emerge then as a manifestation of friction in a many-body quantum system. Our considerations may also explain why strongly localized granular metals are likely to show electron-glass effects while semiconductors are not. 相似文献