[en] In studies of phase equilibria in the U-Co-Ga system at 600 degrees C, the authors found a ternary compound close in composition to U₂Co₂Ga. A sample of composition U₄₂Co₄₀Ga₁₈ was prepared by arc-melting a mixture of high-purity U (99.4%), Co (99.99%), and Ga (99.99%) in a purified argon atmosphere. The sample was homogenized at 600 degrees C for 720 h in an evacuated quartz tube and then quenched in cold water. In structure determination, the authors used a DRON-4-07 powder X-ray diffractometer (CuK_α radiation, 0.02 degrees 2θ scan step) and the CSD software package. The X-ray diffraction pattern showed tetragonal symmetry, with lattice parameters obtained from least-squares refinements a = 0.707729(5) and c = 0.34707(4) nm

[en] Langatate crystals with the nominal composition La₃(Ga_0.5Ta_0.5)Ga₅O₁₄ grown by Czochralski pulling along <0001> have been studied by X-ray and neutron diffraction before and after post growth annealing in air and vacuum. Their compositions are determined, the relationship between the Ga/Ta ratio and unit-cell parameters is established, and their color (colorless, yellow, and orange crystals) is shown to depend on their oxygen content and the growth and annealing conditions. Vacuum annealing at sufficiently high temperatures leads to precipitation of a green phase, La(Ta,Ga)³⁺O₃. (authors)

[en] An analysis of data collected over five years on the thermal conductivity, thermal EMF and Hall coefficient, magnetic susceptibility at 30-300 K, specific heat, and theoretical work devoted to high temperature superconductivity in oxide superconductors belonging to the systems Y-Ba-Cu-O, Bi(Pb)-Sr-Ca-Cu-O, Tl-Ba-Ca-Cu-O has led to an unexpected conclusion. From the optical properties of single crystal superconductors belonging to the systems indicated, the authors conclude that the Bardeen-Cooper-Schrieffer theory is probably not applicable. Apparently Cooper pairs do not exist in high temperature superconductors, but are assumed as an expedient approximation for a description in terms of traditional superconductivity theory. The authors realize that this proposal is controversial and are prepared to present a large amount of data to support it

[en] The importance of investigating the structure and properties of solid solutions of the UO₂-Y₂O₃ system is due to the fact that yttrium is one of the fission products of ²³⁵U, and in the course of the operation of nuclear reactors, it is accumulated in the crystal lattice of uranium dioxide. Only a negligible number of studies of the structure of solid solutions of the UO₂-Y₂O₃ system are known up to now; most of them were performed by X-ray crystallography. It was of interest to study the structures of such solutions by neutron diffraction study, which permits a more accurate determination not only of the localization of light oxygen atoms relative to the heavy uranium atoms but also of the chemical composition of the sample. In neutron diffraction analysis it was shown that when Y₂O₃ is inserted (up to 10% by weight) into the uranium dioxide lattice, solid solutions with chemical compositions close to the stoichiometric oxygen content and a crystal lattice of the CaF₂ type with weak tetragonal distortion are formed

[en] A³B⁶ (A³-Ga, In; B⁶ - S, Se) compounds are interesting promising materials for semiconductor detectors for elementary particles and hard electromagnetic radiation. In the present paper, the authors present the results of an investigation of the effect of 1.3-MeV γ-rays on the photoconductivity (PC) of single crystals of undoped GaS and GaS doped with ytterbium. In the experiments, the authors employed GaS(Yb) single crystals (the Yb concentration was equal to 0.05 at. %), grown by the method of directed crystallization. The specimens were irradiated at room temperature in stages from a ⁶⁰Co source. Before and after each portion of irradiation the authors determined the ratio R_d/R_ell and measured the PC spectra in the wavelength range 300-1000 nm. 3 refs., 1 fig

[en] The critical-current density j_c in ceramic superconductors is strongly dependent on texture, which is determined by the orientation of ceramic grains with respect to the specimen axes and by the misalignment between grains. Y ceramics with prolate grains aligned parallel to the long axis of the specimen were obtained by melt solidification. Such ceramics exhibited j_c = 18500 A/cm² at 77 K in zero magnetic field. Texturing was also achieved by rolling Ag-sheathed powder of superconducting ceramics. This method ensured critical current densities (2-7) x 10³ A/cm² in Y, Bi, and Tl ceramics. In flat ceramic samples, the grains of a superconducting phase were oriented in such a way that the crystallographic c axis was perpendicular to the rolling plane. In this work, the authors studied the effect of rolling deformation on the current-carrying capacity j_c and density p of metal-sheathed YBa₂Cu₃O_y ceramics that were first subjected to hydroextrusion and drawing at ∼20, 550, and 700 degrees C. The data obtained for j_c and p were compared with the texture factor

[en] Since information about stacking faults in refractory compounds is extremely limited, this work attempts to study deformation-induced stacking faults in fcc refractory materials, viz., titanium and vanadium nitrides. The nitrides studied were subjected to plastic deformation during synthesis. Titanium and vanadium nitrides were synthesized using electrolytically pure titanium and vanadium. The specimens were x-rayed and the reflections were recorded from the (111) and (200) planes of the titanium and vanadium nitrides. It is shown that the magnitude of lattice microdistortions in titanium nitride synthesized during vibratory milling is considerable, indicating the occurrence of plastic deformation, which is not subject to recrystallization effects. When this method is used to synthesize titanium and vanadium nitrides, stacking faults are formed in the lattice; these faults are distinguished by x-ray phase analysis methods. The high value of the energy of stacking-fault formation in titanium and vanadium nitrides is due to the characteristic features of the chemical bond

[en] The physicochemical properties of europium and ytterbium chalcostibnites and bismutites are shown. The temperature dependences of the electrical conductivity of EuSb₂S₄, EuSb₂Se₄, and EuSb₂Te₄ are shown with the thermo-emf. From the x-ray phase analysis of the materials studied, it was established that they crystallize in the rhombic system with the formation of stibnite-like structures. Crystallochemical analysis of ternary tellurides of rare-earth elements with bivalent metals (Pb, Ca, Ba, Sr) showed that they have a face-centered cubic lattice of the Th₃P₄ type. The thermal expansion of compounds of the type EuSb₂C₄ and EuB1₂C₄ (C - S, Se, Te) in the interval 77-400 K was also studied

[en] The authors have performed calculations with an ES-1040 computer to determine the formation conditions for solid solutions of given compositions in relation to the initial material and temperature which stimulated the equilibrium state in the Zr0₂ + m /SUB C/ /SUP C/ + n /SUB N2/ /SUP N/ ₂ system in the range 600-3000 K with a step of 100 K at various pressures. Zirconium carbonitrides of various compositions have been made from initial zirconium oxide, carbon black, and purified dry nitrogen. The data on the synthesis conditions and compositions agree satisfactorily with the model calculations

[en] Elements of the Subgroup-VIB (O, S, Se, Te) of the Periodic Table are used as doping impurities in liquid-phase epitaxy of GaP. To carry out controlled doping during this process the elements were introduced into a thin layer of gallium solution, contacting the substrate through the vapor phase. The authors determine the equilibrium constants of the reactions upon direct dissolution of Subgroup-VIB elements into gallium, situated in the vapor phase in the form of diatomic molecules or a hydride (fluoride) compound. The effective distribution coefficients of oxygen, sulfur, selenium, and tellurium as functions of the crystallization temperature are shown for S, Se, Te, and O