Peculiarities in the X-ray Spectral Microanalysis of the Sn?Te?I System

This is an examination of the methodological specificities of the roentgenospectral microanalysis of the Sn Te I system, involving the application of a graphoanalytical method used in the analysis of ternary systems according to data calculated for the binary ones. The calculations were made on an ES 1060 computer in FORTRAN-4. The calculations are for different selection angles of the microanalyzer, and for a broad interval of values of the accelerating voltage. In this manner the method offered is applicable to any type of microanalyzer, and not only to the Cameca MS-46 used by us.     

Mass transfer during growth of Ga?In?P?As solid solution in the equilibrium cooling growth technique

Kinetical analysis of crystallization of Ga In P As solid solutions grown by equilibrium cooling growth technique was performed. Theoretical data were compared with experimental data on LPE of the material. The dependencies of layer thickness, lattice mismatch variation between the substrate and layer and energy gap in the layers lattice matched to InP were calculated for different growth temperatures.     

Liquid Phase Epitaxy of SiC in the System Si?Tb?SiC by Temperature Gradient Zone Melting (I). Investigation of Solubilities in the System Si?Tb?SiC

In the paper which is divided into three parts the liquid phase epitaxy of SiC by temperature gradient zone melting with the solvent Si Tb is discussed. In the first part the solubility of SiC at different initial compositions of the Si Tb solvent is studied in the temperature range 2000–2500 K.     

Stabilization of the melt composition in Ga?Al?Sb?As

In this work we present a new effect of stabilization of the Ga Al Sb As melt composition when it is in contact with the GaAs substrate. It was found that the As content in the Ga Al Sb As melt did not depend on the initial Sb concentration when the liquid phase was formed by saturating the Ga Al Sb melt from the GaAs substrate. This effect is supposed to be due to the change in phase equilibria conditions caused by large lattice mismatch between the substrate and the solid in equilibrium with the liquid.     

Effect of Particle Size on the Ice Nucleating Ability of AgI?AgBr?CuI System

The effect of particle size on the ice nucleating behaviour of AgI-AgBr-CuI system has been studied for the first time. Six samples of different molar ratios and five sizes in each sample are considered in the present study. It is found that the nucleation temperature is the highest for particle size in the range of 60 ± 5um.     

Thermal Expansion and Superconductivity in Alkali Metal- and Silver-doped Bi?Sr?Ca?Cu?O System

Samples with the nominal composition Bi₂Sr₂CaCu₂O_y with na doped at the Ca site and K doped at the Sr site are prepared by solid state reaction method. From the X-ray diffraction data it is found that all the the samples have exhibited a single phase 2212. The D.C. electrical resistivity data show that for Na-doped samples the T_c (zero) varies from 80 K to 85 K and for K-doped samples it is from 79 K to 82 K. The loss of oxygen from these samples around 400°C was confirmed by high temperature dilatometry. The variation of the thermal expansion coefficient (“α”) with temperature for different alkali dopings are discussed. Also the samples with the nominal composition Bi₄Sr₃Ca₃Cu_4−xAg_xO_y (with x = 0, 0.1, 0.2, 0.3) were studied.     

Effect of the relative content of Y,Ba, and Cu on the superconducting transition characteristics of the Y?Ba?Cu?O System

By varying the content ratio of the initial products, nine compounds of the Y Ba Cu O system have been produced. These were studied to find their T_c values, critical currents j_c at 77 K and effects of compression stress on the U(j)-curves. Mechanical loading has been found to result in a shift of the U(j)-curve towards a larger current. A correlation between the critical current value, the slope of the U(j)-curve, and the stress induced shift is shown to exist. Samples with equal absolute deviations from the stoichiometric composition reveal close properties, the better the smaller is the deviation.     

Vapour Phase Epitaxy of GaxIn1−xAs in the Ga?In?HCl?AsH3?H2-System Using a Mixed Ga/In Source

The mixed crystal composition of Ga_xIn_1−xAs layers is analysed as a function of the composition of a mixed Ga/In source during VPE in the hydride system. Experimental results are compared with thermodynamic calculations. Both thermodynamics of the deposition reactions and thermodynamies of the souree reactions are considered in the calculations.     

Preparation of Al?Ga?P?As heterostructures

The present paper reports on the results of an investigation of crystallization of multilayer structures with a narrow-gap semiconductor surrounded by two wide-gap ones in the Al-Ga-P-As system on GaAs and GaP substrates. Influence of the lattice parameters' difference on the value of thermal stress in structures with a composition gradient was determined by the bend of structures separated from the substrate. It has been proved that with the P concentration in solid solutions being less than 1% heterojunctions with less tensions than in the Al–Ga–As system are available. A new method of obtaining Al_xGa_1–xP_yAs_1–y solid solutions with the concentration of P proportional to that of Al has been worked out on the basis of which multilayer heterolight-emitting structures have been prepared.     

Electrical Conductivity and Thermoelectric Power of Lithium?Zinc Ferrites

Electrical conductivity (σ) and thermoelectric (Q) of polycrystalline lithium-zinc ferrites of different compositions was investigated as a function of composition and temperature. Plots of log (σT) versus 10³/T are almost linear and show a transition near the Curie temperature. The activation energy. in the ferrimagnetic region is in general less than that in the paramagnetic region. The carrier concentration and mobility of charge carriers has been discussed as a function of composition and temperature.     

Solid Solutions in the FeNbO4?TiO2 System

Thermal decomposition of freeze-dried complex oxalate precursors allows the synthesis of crystalline phases in the FeNbO₄ TiO₂ system at relatively low temperature. This system shows not only a rutiletype, but also a wolframite-type solid solution (ss), which exists at lower temperatures. The temperature of the reversible transformation wolframite-rutile decreases with increasing TiO₂ content.     

On Peculiarities of Chemical Bond in the Zn?P System from the Magnetic Susceptibility Data

The measurements of magnetic susceptibility of the Zn-P system compounds have been performed and their Langevin diamagnetic component has been calculated. The influence of the degree of covalency of bonding on the value of diamagnetic constituent of the compounds has been investigated. It is shown that the semiconductor compounds of the Zn-P system have preferably covalent character of chemical bond.     

Investigations of phase relations in the system CaO?Na2O?K2O?P2O5

The lattice constants of the compound Ca₂NaK(PO₄)₂ have been studied at room temperature using an X-ray powder diffractometer and also in the temperature range from 20 up to 1000 °C by Guinier-Lenné-technology. A hexagonal lattice with the parameters a₀ = 5.4367 Å and c₀ = 7.3125 Å and a cell volume of 187.18 ų has been determined for the high temperature phase, existing from 670 °C upward. At temperatures below 670 °C a superlattice structure is formed by tripling the axis a, a ′, and c so that it results in a hexagonal superlattice structure cell with the lattice constants of a₀ = 16.311 Å and c₀ = 21.939 Å and a cell volume of 5054 ų.     

Study of the reversible martensitic transformation in Cu?Zn?Al alloy by positron annihilation

The positron lifetime measurement to investigate phase transformations: martensitic phase (MP) ⇔︁ parent phase (PP) in Cu Zn Al alloy has been used. We have observed the generation of new defects by MP → PP transformation; these defects are liquidated by martensitic transformation. This effect is only observed in case of high concentration vacancies in alloy. In order to explain the nature of these defects we take into consideration the supervacancies idea.     

Liquid Phase Epitaxy of SiC in the System Tb?Si?SiC by Temperature Gradient Zone Melting (II). Liquid Phase Epitaxy of SiC from Tb?Si Solvent

The liquid phase epitaxy of SiC by the gradient temperature zone melting in the Si Tb solvent is studied. A new variant of this growth method is presented. The comparison of the new variant with the previous one shows that the new variant allows for epitaxial layers with significant better electrophysical properties. It is easier and can be carried out at lower temperature.     

The influence of small deviations from stoichiometry on the properties of Y?Ba?Cu?O superconductor ceramics

According to a central composite design samples with deviations from stoichiometry YBa₂Cu₃O_7−x of ±2.5 wt% in the ingredients were prepared. The influence of these deviations on phase content, superconducting properties and microstructure of the ceramics was studied.