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.     

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.     

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.     

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.     

Epitaxial Deposition of GaAs in the Ga(CH3)3?AsH3?H2 System (III) Heteroepitaxy on Isolating Substrates

Epitaxial growth of GaAs has been achieved on CaF₂, α-Al₂O₃ and spinel substrates. X-ray investigations showed well defined relations between layer perfection and the quality of substrate material. The formation of epitaxial layers in pyrolytic deposition processes is discussed in terms of supersaturation and its influence on nucleation and layer growth.     

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.     

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.     

The Distribution Coefficient of Isomorphous Admixtures for KCI?KBr?H2O,K2SO4?(NH4)2SO4?H2O and KNO3?NH4 NO3?H2O Systems at 298 K

For the systems KCI KBr H₂O, K₂SO₄4-(NH₄)₂H₂O and KNO₃ NH₄NO₃ H₂ O equilibrium investigations have been performed and the distribution coefficients of isomorphous admixtures have been determined. For each solid solution the changes of the distribution coefficient D, the dependencies between the values of the real and ideal distribution coefficients and the directions of energetic changes in these systems during the co-crystallization of isomorphous and isodimorphous admixtures have been discussed.     

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.     

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.     

Epitaktische Abscheidung von GaAs im System Ga(CH3)3?AsH3?H2 (I) Autoepitaktische Abscheidung

Some aspects of Ga(CH₃)₃/AsH₃/H₂ pyrolysis are described. The quality of the epitaxial GaAs layers on GaAs substrates is examined by chemical etching, X-ray technique and observation of the surface morphology. The investigations show a relation between the quality of the layers and growth conditions (As/Ga-proportion, substrate temperature).     

Preparation and phase characterization of the SrCl2?EuCl2 and SrCl2?EuCl3 systems

The SrCl₂ EuCl₂ and SrCl₂ EuCl₃ systems were investigated over the full composition ranges by the Guinier powder X-ray diffraction technique. In the strontium chlorideeuropium dichloride system the solubility from the both ends of reactants was found when fast cooling of the melt was used. In the strontium chloride-europium trichloride system a solid solution for the composition region up to 20 mol per cent of EuCl₃ and two new intermediate chlorides, Sr₄EuCl₁₁ and Sr₉Eu₅Cl₃₃, were observed. The compounds crystallize in orthorhombic symmetry with lattice parameters of 7.220(2), 35.15(1), 6.790(4) and hexagonal 12.854(4) and 24.702(8), respectively.     

Thermoelectric Behaviour of Some Phases in the In?Se System

The differential e.m.f. of In₆Se₇ single crystals as a function of temperature have been measured. The electron to hole mobility ratio is determined to be μ_n/μ_p = 3.62. The effective masses of electrons and holes are 4.21 × 10⁻³³ kg and 9.01 × 10⁻²⁹ kg, respectively. The diffusion coefficient for holes and electrons as well as the diffusion length of free charge carriers have been determined.     

Epitaxial Deposition of GaAs in the Ga (CH3)3?AsH3?H2-System (IV) Thermodynamic and Kinetic Considerations

For reactions taking place between the species Ga, As₂, As₄, AsH₃, and H₂, the equilibrium constants were calculated. The discussion indicates that factors other than thermodynamic considerations significantly influence the deposition process. Kinetic investigations demonstrate the importance of the As:Ga proportion that has to apply for perfect layer growth. The mechanism of deposition is in correspondence with a Langmuir-Rideal Model. For high substrate temperatures a homogeneous reaction in the vapour phase can-not be excluded.     

Entmischung im System SnO2?TiO2. Will Kleber zum Gedenken

Exsolution in mixed crystals SnO₂ TiO₂ containing 80 mole% TiO₂ are investigated at temperatures up to 940°C and under pressures of 1,5 and 3 kbars. The existence of an unstable interim phase consisting of lamellae rich in SnO₂ and rich in TiO₂ observed by STUBICAN and SCHULTZ in crystals containing 50 mole% SnO₂ is confirmed. It is shown that the explanation as periodic density fluctuation is wrong. The “side bands” observed in X-ray powder diffraction patterns are due to the different c-lattice-constants. High pressures have a strong retardation effect on exsolution, due to the decrease of the diffusion constant. The presence of water increases the diffusion rate of ions considerably; in powder diffraction the interim phase can only be observed with the aid of asymmetric X-ray reflections. The quantitative interpretation of X-ray diffraction pattern is given in the case of the interim phase. The averaged thicknesses and the Ti-, Sn-concentrations of the lamellae can be given.