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941.
In our work single crystals of Mg4.5Na7(P2O7)4 were prepared, pulverized, pressed into pellets and sintered in order to measure the electrical conductivity of polycrystalline specimens. The conductivity was also measured on glassy specimens obtained by the melting of previously prepared crystals. The electrical conductivities at 25°C with values of the order of 10−16 Ω−1 cm−1 for polycrystalline samples and a value of the order of 10−14 Ω−1 cm−1 for glass, show that the glassy phase of Mg4.5Na7(P2 because of its greater molar volume and loosely packed structure, is a better matrix for ionic motion. 相似文献
942.
We study first-order definability in the latticeL of equational theories of semigroups. A large collection of individual theories and some interesting sets of theories are
definable inL. As examples, ifT is either the equational theory of a finite semigroup or a finitely axiomatizable locally finite theory, then the set {T, T
ϖ} is definable, whereT
ϖ is the dual theory obtained by inverting the order of occurences of letters in the words. Moreover, the set of locally finite
theories, the set of finitely axiomatizable theories, and the set of theories of finite semigroups are all definable.
The research of both authors was supported by National Science Foundation Grant No. DMS-8302295 相似文献
943.
944.
V. Kažukauskas 《Applied Physics A: Materials Science & Processing》1995,60(5):509-514
We report the investigation of the Photo-Magneto-Electric effect (PME) in semi-insulating Liquid-Encapsulated (LEC-) grown GaAs crystals, using both intrinsic and impurity excitation. The role of the majority and minority carriers on the conductivity phenomena was evaluated and the lifetimes of electrons and holes were determined depending on excitation conditions. Anomalously high PME voltages, reaching in some cases some volts, were measured, which demonstrate a sharp drop in the temperature region 320–360K. The observed changes are discussed supposing that the influence of the non-homogeneous defect structure of the samples is essential. 相似文献
945.
946.
Temperature dependence of electronic and ionic components of electric conductivity and dielectric permittivity of amorphic compounds Ag0.25Sb0.25S0.5, (AgSbS2)0.95· (SbSI)0.05 and (AgSbS2)0.9·(SbSI)0.1 in the temperature range of 290–380 K have been investigated. The experimental data show that glasses investigated are solid electrolytes. Ionic conductivity as well as dielectric permittivity of the glasses Ag-Sb-S may be changed by introduction of SbSI. 相似文献
947.
The kinetics of the silicon/hydrogen low-pressure discharge system have been measured using a flow technique and mass spectrometry. Results show that at long residence times the system operates under a partial chemical equilibrium even though it is not at thermodynamic equilibrium. The present work indicates that the decisive parameter controlling the structural properties of the deposit (i.e., the formation of either amorphous or microcrystalline silicon) is the departure of the system from the partial chemical equilibrium. 相似文献
948.
949.
950.
Self-consistent-field (SCF) calculations have been performed by means of a pseudopotential (PP) technique on medium-size Ben clusters (n = 7, 10, 13). Correlation effects have been taken into account through multireference double-excitation configuration-interaction (MRD CI) procedure. Particular attention has been paid to the existence of Be clusters with many nearly degenerated states of singlet and triplet spin multiplicity. The SCF ordering of these states is frequently reversed in CI. Planar and non-planar Be clusters show comparable high stabilities caused by a strong sp hybridization. Two sections of the potential energy surface for the interaction of a H atom with the Be7(7,0) cluster have been determined. Two regions of low energy found in this energy surface: one inside and the second outside the cluster border, are separated by an energy barrier. The CI results, indicating the directly overhead position as the absolute minimum of the surface, are in qualitative agreement with previous SCF studies on similar systems. The modifications of the cluster geometry (shrinkage or relaxation) caused by the interaction with the H atom in the directly overhead position are found to be very small. 相似文献