Journal of Physics and Electronics

11-18

Authors: V. N. Gorev, A. I. Sokolovsky

We consider a slightly non-uniform one-component gas with weak potential interaction. The basis of the investigation is the known kinetic equation in the case of small interaction which is truncated up to the second order of smallness. This equation contains a nonlocal collision integral of the second order in small interaction. In this paper we consider the hydrodynamic stage of the system evolution, and, in contrast to the standard hydrodynamics, we take into account the non-locality of the collision integral. We propose the following set of the reduced description parameters which are the densities of the conserved quantities: the particle number density, the momentum density, and the total energy density. It should be stressed that in contrast to the standard hydrodynamics, the kinetic energy is not conserved, and only the total system energy is conserved if the nonlocal collision integral is used. Definitions of the system velocity and temperature are proposed; it should be stressed that the proposed temperature definition is based on the total system energy rather than on the kinetic one. The hydrodynamics in the leading order in small gradients is investigated, and it is shown that the system one-particle distribution function in the leading-in-gradients order coincides with the Maxwellian one. Particle number density, velocity and temperature time evolution equations (hydrodynamic equations) are derived in the non-dissipative case. The leading-in-interaction orders of the obtained equations coincide with the corresponding equations in the framework of the standard hydrodynamics. The corrections of the first and second order in small interaction are also obtained.

29-34

Authors: V.V. Kovalchuk

In this paper, we discuss in detail the theoretical results obtained with using the local functional density method in parameteric approximation of silicon clusters. One of the main conclusions is that the comparison between theory and experiments shows the possibility of different radiative channels for the recombination in porous silicon.

39-44

Authors: O. I. Kushnerov, V. F. Bashev

The paper explores the structure and magnetic properties of multicomponent high-entropy Al-Cu-Fe-Ni-Si alloys in as-cast and splat-quenched state. This alloy system is characterized by the absence of expensive components, such as Co, V, Mo, Cr, usually used for the production of high-entropy alloys while its characteristics are not inferior to those of more expensive alloys. Components of the studied high-entropy alloys were selected taking into account both criteria for designing and estimating their phase composition, which are available in the literature and based on the calculations of the entropy and enthalpy of mixing, and the difference between atomic radii of components as well. The alloy films were fabricated by a known technique of splat-quenching. A cooling rate estimated by film thickness was ~ 106 K/s. Experimental results reveal that the studied alloys except the Al0.5CuFeNi one are multiphase, with the structure consisting of disordered BCC and FCC solid solutions. The Al0.5CuFeNi alloy has only FCC phase. The leading role in determining the type of solid solution formed in the studied high-entropy films obviously plays an element with the highest melting point. All of the investigated multicomponent films are soft magnetic materials as indicated by low values of coercivity, while most of the as-cast alloys are hard-magnetic.

53-56

Authors: T. V. Kruzina, S. A. Popov, Yu. N. Potapovich, A. S. Rutskyi

Na0.5Bi0.5TiO thin films were grown on heated to 200°С Pt/TiO2/SiO2/Si substrates by ex-situ method with high-frequency (13.56 MHz) magnetron deposition. Thermal treatment of the films was carried out at 650°С, 700°С and 800°С. X-ray diffraction investigations showed the films were poly-crystalline and contained additional phase. In the films annealed at 700°C two dominating conduction mechanisms were observed: ohmic at the fields Е < 8 kV/cm and Schottky emission in the field range of 30 – 70 kV/cm. It is also observed that the increase of the film annealing temperature to 800°С leads to the increase of leakage currents. It is assumed that high values of the leakage currents were attributed to the presence of both structure defects and additional unknown phase.

63-68

Authors: R. I. Lavrov, V. R. Kolbunov, V. F. Bashev

Electrophysical properties of near-surface layer of ZnO varistor ceramics forming during high-temperature annealing in oxidizing gaseous atmosphere are studied. Microstructure of near-surface layer and its electrical properties have features which are determined by an increased concentration of oxygen at surface of pressed ceramic billets in comparison with bulk during annealing. From the data of electron raster microscopy of cross-chipping of varistors, it is defined that the average value of thickness of near-surface layer is 40 μm. It is found that the specific resistivity value of near-surface layer is 5.3·1012 Ω·cm. The electrical capacitance of near-surface layer is calculated from capacitance measurement data for varistors containing such layer under two electrodes and without layers. It is shown that the electrical capacitance of near-surface layer exceeds that of varistor by more than an order. Conclusion is made that the near-surface layer gives a weak contribution to dielectric properties of ZnO varistor ceramics. However contribution of this layer to electrical conductivity of ceramics in pre-breakdown region is significant.

73-76

Authors: O. V. Kovalenko, O. V. Khmelenko, Ye. G. Plakhtii

It has been investigated the influence of heat treatment with the following temperins on the integral photoluminescence spectra and on the individual bands of this spectra. It has been showed the correlation between the changes of intensity of photoluminescence individual bands and real structure of crystal, controlled with the help of EPR method. The basic changes of photoluminescence and structural properties have threshold nature. They begin to show up at temperature of annealing T > 650o С. The maximum intensity of integral photoluminescence spectrum was observed in the region of phase transition crystal structure of zinc sulphide.

83-88

Authors: V. V. Ovsyanikov, D. M. Svynarenko, E. R. Beznosova, L. Z. Tsipko

Approximate and rigorous methods and results of calculations of electrical characteristics of rod arbitrarily curved antennas of the microwave range are investigated with the purpose of widening their varieties and increasing the accuracy of calculations of electrical parameters. An approximate calculation of the antennas is performed by the equivalent long line method, rigorous – by the integral equation method with respect to the distribution of the complex current at the antenna. An algorithm for the step-by-step development of curved rod antennas with included various concentrated loads and excitation nodes at arbitrary points are proposed. It is concluded that approximate methods are useful for a preliminary rough estimate of the input parameters of the antennas, and also as an initial approximation for their parametric synthesis and analysis. But strict methods can significantly expand the variety of studied antennas and improve the accuracy of calculations of their electrical parameters. A method is proposed for obtaining a stable solution of an integral equation by diagonalizing the matrix of coefficients of a system of equations. Basing on the results of the investigation of these antennas, new designs have been developed, a number of which have been introduced into production and operation. It is noted that for the first time in world practice the method of an integral equation described in this article for calculating such antennas has outpaced the development of known analogous methods and corresponding computer programs.