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The electrical conductivity (s) of a dispersed mixture consisting of quartz sand and graphite of identical granulometric composition is investigated as a function of the volume concentration (x) of graphite. It is shown that this dependence is well described analytically by the equations of the percolation (00.5) theories. Such a system can be represented by a model of R network.

The dependence of the electrical conductivity of a mixture of finely disperse graphite with quartz sand and moist quartz sand on the composition is investigated. It is shown that, in the region of critical and near-critical concentrations of the conducting component, the dependence is satisfactorily described by two power-law equations of flow theory with two different threshold values of the conducting-phase concentration. In this concentration range, the conductivity of the sandgraphite system is satisfactorily modeled by a lattice bond problem. The electrical transfer in the sand-KCl solution system may be modeled by a lattice point problem in the representation of the moist system as a mixture of dielectric particles coated with an electrolyte film (conducting particles) and dry dielectric particles (nonconducting particles).

The behavior of the dielectric permittivity of a mixture of disperse materials is investigated for a change in the volume content of the component with a high value of the dielectric permittivity. An analysis is performed from the viewpoint of computing the dielectric permittivity of such mixtures. A formula is proposed for computation of the dielectric permittivity of mixtures of disperse materials with water.

A method of measuring the complex dielectric constant of a mixture composed of a disperse substance and water by insertion of dielectric spacers between the electrodes and the investigated substance is discussed. This system exhibits relaxation of the Maxwell-Wagner type in the conductivity range 10-8–10-2 O-1·m-1. By constructing and analyzing Cole-Cole diagrams it is possible to determine the complex dielectric constant of mixtures with a water content of 1–100 wt.% in the frequency range 102–107 Hz.

The dependence of the electrical conductivity and dielectrical permeability for dispersion mixtures of a dielectric and a conductor (moist top) on the composition and properties of the components have been studied in the frequency range 0 to 107 Hz. It is shown that for the moisture content, which allows one to model the soil by the two-phase air -water system, the obtained dependences are satisfactorily described by the equations of the percolation theory.

An analysis is made of the existing waveguide methods (short-circuit, “infinite” layer, variable reactive load, “direct” determination of the wavelength and pattern of the electromagnetic field in the investigated material) as applied to disperse materials characterized by high losses. A comparison of the short-circuit method with the direct measurement of the propagation constant is used to show that the latter is preferable when applied to materials with large values of the permittivity (in excess of 10) and a large loss-angle tangent (in excess of 0.1). This method does not require complex mathematical calculations and makes it possible to determine unambiguously the permittivity, whereas the values of the loss-angle tangent are physically more reasonable.

In the paper an analysis is presented of the dependence of the position of the low-frequency dispersion region of a semiconducting heterogeneous specimen-spacers system on the volume concentration of the conducting component, the thickness of the specimen, the thickness (capacity) of the spacers. It is concluded that there exists a surface capacity due to regions of the nonconducting phase of the specimen confined between the spacers and a conducting infinite cluster.

The electrical conductivity of a dispersed mixture of sand and graphite of various granulometric compositions (filling factor k=0.74) was investigated. It is shown that for mixtures which have pore sizes in a structure of dense packing of one component do not exceed the particle sizes of the other component and the threshold volume concentration of the conducting phase is completely determined by the ratio of the particle sizes of both phases. An analytic expression relating the volume threshold concentration of the conducting component and the particle sizes of the components is obtained by solving the bond problem.

The behavior of the dielectric permittivity of a mixture of disperse materials with change in volume content of the component with high dielectric permittivity (water) and temperature is investigated. An analysis of the results is presented. A formula is given for the calculation of the dielectric permittivity of moist disperse materials as a function of the temperature.

The paper considers the effect of nonuniform structure in the centers on the ESR spectrum for the case of axial anisotropy in the g factor; it is shown that if (s2? >s2?, ?¦ >??), the model enables one to describe fairly completely the spectrum of a glass containing 33% Na2O and 67% SiO2. Good agreement with all experimental evidence is not obtained for potassium silicate glasses.

Summary 1.A forsterite ceramic with copper introduced from solution contains two types of Cu2+. One of these gives a broad nearly isotropic line with geff=2.18, which is due to Cu2+ in a tetragonally deformed octahedron of oxygen ions. The Jahn-Teller effect, which is responsible for this deformation, is averaged by reorientation of the tetragonal axis. The second type is seen only at low temperatures and has a resolved HS; it is due to Cu2+ in an analogous environment, but with the reorientation frozen-in.2.The relation between the two types of center is the same throughout the volume of the specimen.3.Cu2+ enters the vitreous phase on firing at 1000 ° C.4.Ordering of the local symmetry of the environment of the copper occurs as the firing temperature is raised.

A method is discussed in this paper, allowing to separate the component of ESR spectral line width due to a g-factor variation from center to center in materials with random spin orientations. Spectra ofa andß centers in alkali-silicate glasses are analyzed by this method.

The EPR spectrum of irradiated alkali silicate glasses in the range of g-factors between 2.000 and 2.025 was analyzed using an M-20 computer. It was shown that the observed form of the spectrum for glasses with small alkali contents can be represented as the superposition of three lines with an axially anisotropic g-factor.

1.The EPR spectrum of irradiated potassium silicate glasses having slight alkali contents (g varies from 2.000 to 2.025) cannot be produced by superimposing two lines, one of which is typical of glasses having a large alkali content a1, and the other of which is due to a paramagnetic center having S =1/2 and complete g-factor anisotropy.2.The agreement with experiment is better if we assume a completely anisotropic g-factor for a3 (one of the three lines a1, a2, a3).

An EPR spectrum which may be assigned to the V4+ ion has been observed in vanadium-tellurite glasses. Tetravalent vanadium enters the tellurium-oxygen framework in the form of octahedral [(V4+O)O5] complexes.