X-ray powder diffraction investigations of solid solutions in the KCl?KBr?H2O system at 298 K

The measurements of crystal lattice parameters (a) of solid solutions being formed in the system KCl KBr H₂O at 298 K were conducted. The volumes (v) of unit cells and the densities (ϱ) of mixed crystals K(Cl, Br) were calculated. It was confirmed that in the investigated system continuous solid solutions were formed. The lattice parameters of these crystals formed from aqueous solutions of salts as well as from molten salts and also calculated by Durham-Hawkins method were nearly identic.     

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.     

X-ray powder diffraction investigations of solid solutions with limited miscibility in the KNO3?NH4NO3?H2O system at 298 K

The measurements of crystal lattice parameters (a, b, c) were conducted and the volumes (v) of unit cells of solid solutions forming in the system KNO₃ NH₄NO₃ H₂O at 298 K were calculated. It was established that in this system at 298 K two series of solid solutions were formed: the mNH₄NO₃ · n(KNO₃ · 2 NH₄NO₃) solid solution with the gap of miscibility and the kKNO₃ · l(KNO₃ · 2 NH₄NO₃) solid solution with one-sided limited miscibility.     

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.     

Growth studies of YVO4 crystals (II). Changes in Y?V?O-stoichiometry

Incongruent vanadium oxide vaporization of yttrium orthovanadate (YVO₄) melt generates changes in both oxygen and yttrium-vanadium (Y V) stoichiometry. Slightly modified YVO₄ or YVO₄ + Y₈V₂O₁₇ phases are formed from continuously changing melt systems depending on their starting compositions. The occurrence of Y₈V₂O₁₇ in yttrium orthovanadate crystal fibers grown by laser heated pedestal growth (LHPC) technique can be simply eliminated by utilization of suitable V₂O₅-excess starting compositions. In contrast, the oxygen-deficient YVO_4–x black phase is an inherently oxygen deficient phase with limited solid solution in the YVO₄ YVO₃ subsystem of Y₂O₃ V₂O₅ V₂O₃ complex ternary phase diagram close to the congruent YVO₄ composition (49.3 mol% V₂O₅–50.7 mol% Y₂O₃). The greater oxygen deficiency YVO_4–x specimens have smaller lattice parameters as determined from detailed XRD data. Ceramic feed rod and fiber crystal grown from the feed rod with slight yttrium oxide excess starting composition were characterized by electron microprobe analysis. Changes in both Y V and oxygen stoichiometry were observed along the fiber, due to double limited solid solution system of three dimensional ternary phase diagram. Consequently, both the presence of Y₈V₂O₁₇ phase and change of Y V stoichiometry over oxygen deficiency cause difficulties for YVO₄ crystal growth from yttrium oxide excess melt.     

Synthesis of AgI?AgCl?CuI solid solutions for ice nucleation studies

Lattice parameter calculation and the nucleation temperature of AgI AgCl CuI system are reported in this study. By vacuum fusion three samples of different molar compositions were prepared. The formation of the cubic solid solution of the above system was confirmed by X-ray analysis. It is found that the 50:25:25 mole% composition of AgI AgCl CuI has the highest nucleation temperature of −1.0 °C, which is far greater than −2.53 °C, −4.02 °C and −2.26 °C for pure AgI, AgCl, and CuI, respectively.     

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.     

Texture investigations of Mn?Al magnets by neutron time-of-flight diffraction

In the present work the connection between magnetic properties and texture of two samples of the tetragonal Mn Al phase is investigated. The specimens have been prepared by different cold deformation methods to get various texture types. For texture analysis neutron time-of-flight technique has been applied. Some aspects of the mathematical treatment of experimental data has been discussed. The main texture components in the inverse pole figures are inclined with respect to the direction of easy magnetization. Therefore, improved magnetic properties of the material can be expected using more optimal preparation techniques.     

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.     

Isochronal Phase Transformation in Al?Zn?Cu Alloys

Two Al-Zn alloys with 40 wt% and 74wt% Zn, respectively, and copper additions between 0 and 10 wt% were investigated by means of X-ray diffraction methods, X-ray small angle scattering, resistivity, and dilatometric investigations during continuous cooling from 673 K applying a cooling rate of 2 K/min. It was found that copper additions lower the driving forces for the onset of the homogeneous nucleation after crossing the range of homogeneity, but accelerate the formation of the η-phase. The reasons for this facts are discussed.     

A microstructural examination of Zn?Al?Cu alloys

A microstructural examination of a Zn-11 wt% Al-1 wt% Cu alloy in dependence on the applied heat treatment was carried out by means of scanning electron, transmission electron and optical microscopy as well as X-ray investigations.     

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.