Microhardness studies of K1−xRbxCl crystals

The microhardness measurements have been made on pure crystals of KCl, RbCl and mixed crystals of K_1−xRb_xCl. Microhardness varies non-linearly with composition being maximum near at the eqimolar composition. Microhardness values calculated from lattice parameter data are in good agreement with experimental data. The difference in the size of the ion constituting the mixed system is responsible for the internal strains giving rise to imperfections and inturn responsible for the non-linear variation of microhardness with composition.     

X-Ray-Interferometric Determination of Å-scale Lattice Shifts at the Surface of Silicon Crystals — the Analogue to Light-Optical Interference Microscopy

The paper presents a new imaging method based on a refined and better stabilised X-ray Michelson interferometer [Appel , Bonse ]. Interference fringes are detected which mark local Å-scale shifts of the lattice at the surface of the interferometer's phase-shifter crystal. Conventional double-crystal topography (DCT), lacking phase information of the beam reflected by the specimen crystal, does not detect mere lattice shifts. The new method appears to be also more sensitive to any combined lattice strain δ ≡ Δd/d + cot θ_B Δθ (θ_B: Bragg angle, d: lattice parameter) present in the crystal layer contributing to the surface Bragg reflection. δ is known to be the dominant part of the DCT image [Bonse , 1958; Bonse , Hartmann ]. The technique presented here is the X-ray analogue to the well known light-optical interference microscope. A possible application is the testing of silicon crystals for minute lattice imperfections causing lattice-incoherent positions of atoms in a surface layer of typical 1 to 10 μm thickness. For instance striations, which under certain conditions arise during crystal growth, cause such incoherence.     

High Temperature Ionic Liquids: Thermal Properties and Dimorphism in [1-(Methoxycarbonyl) Ethyl] Triphenylphosphonium <Emphasis Type="Italic">p</Emphasis>-Toluenesulfonate

Abstract  Investigation of the thermal properties of triphenylphosphonium p-toluenesulfonates, which are high temperature ionic liquids, reveals that they solidify to a noncrystalline material on fast cooling from the melt. During the study, a second crystalline form of [1-(methoxycarbonyl) ethyl] triphenylphosphonium p-toluenesulfonate (form II) has been obtained. Form II is monoclinic P2₁/c, with a = 11.002(5)?, b = 12.793(5)?, c = 18.805(5)?, and β = 102.498(5)°. Comparison with form I reveals the existence of a common robust structural feature involving interactions between cations and anions. Graphical Abstract  Investigation of thermal properties of ionic liquids has revealed a second crystalline form of [1-(methoxycarbonyl) ethyl] triphenylphosphonium p-toluenesulfonate.      

Die Herstellung von einkristallinen Dünnschichten aus Halbleitern mit ausgeprägter Anisotropie durch gerichtete Kristallisation der Schmelze zwischen zwei Substraten

Investigation of monocrystalline thin layers (5 to 150 μm in thickness) of Te and CdSb orientedly grown between two substrates. The form of the solidifying front strongly influencing crystal perfection can be controlled. Thin layers grown with velocities < 0.25 cm · min⁻¹ are monocrystalline with etch pit densities of 6 · 10² cm⁻². The electrical quantities R_H, σ and α of the layers are nearly identical with those of bulk material. Doped monocrystalline CdSb layers had a minority carrier concentration of ∼ 10¹⁴ cm⁻³ at 77°K.     

Etching of Anthracene Cleavages in Sulphuric Acid — Formic Acid Solutions

Crystal etching, though a simple and widely adopted technique for the study of imperfections in a wide variety of materials, the process is not very well understood. The etch pit shapes are controlled by a number of factors, such as, the composition of etchant, the period of etching, the temperature of etching and the symmetry of plane under study. This communication reports observations of etching the (001) cleavage planes of anthracene in sulphuric acid — formic acid mixtures.     

Einsatz der Elektronenstrahl-Mikrosonde bei der Untersuchung der leichtschmelzenden Phasen in Molybdänelektroden zum Glasschmelzen

Investigation were carried out on melting-off phenomena of molybdenum rods during the melting of glasses in electrode furnaces, using the electron probe microanalysis. In the course of these experiments it was found that at the edges of the molybdenum droplets molten-off nickel had deposited with a concentration corresponding to a Mo Ni alloy in the δ-phase. Finally a few hints are given for avoiding such melting-off processes.     

X‐ray diffraction studies of bone apatite under acid demineralization

The analysis of the X‐ray diffraction line broadening used to determine bone apatite crystallite size and lattice microstrain can provide information about the substructure of the bone mineral under differing real or simulated conditions. The paper discusses modifications in the bioapatite crystals observed in the bone subjected to demineralization in a 0.1 N HCl solution. Planar oriented specimens of mature bone with the analyzed surface normal to the longer bone axis were treated for varied immersion times. The crystallite size and the lattice microstrain were determined simultaneously by Fourier analysis of the X‐ray diffraction line profiles. Both were observed to decrease during the acid demineralization. These findings support the idea that the distribution of lattice imperfections in the bulk of bioapatite crystals is highly nonuniform, with crystallite surface regions richer in imperfections dissolving more readily. In addition, an approach is proposed suitable for rough estimation of the reaction front advancement by demineralization‐induced variations in the integrated intensity or shift in the position of the (002) and (004) diffraction lines. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stereometrical X-ray Interferometric Diffraction Topography of Crystal Imperfection

A method for X-ray interferometric investigation of the deformation field of crystal imperfections by means of double and triple interferometers is proposed. It is shown experimentally that by means of double and triple interferometers it is possible to detect segregation lines, displacement lines, and the Moiré patterns of different type imperfections as well.     

The MORIN Transition – a Sensitive Criterion for Testing the Quality of α-Fe2O3

The MORIN transition of α-Fe₂O₃ is quite sensitive to impurities, lattice imperfections and particle size and, therefore, can be used to test the quality of α-Fe₂O₃. If in the material under consideration the MORIN transition has completely taken place at 250 K, the material is pure, undistorted bulk α-Fe₂O₃. For testing this only one Mössbauer spectrum has to be taken at 250 K.     

Zur Züchtung von β-Kupferphthalocyanin-Einkristallen aus der Gasphase

An apparatus useful for many kinds of vapour phase growth used in order to clarify reasons for bad reproducibility and constancy of growth conditions by an growing method known since 1936 and reasons for cavity growth. The characteristics of growth are described dependent on different growing methods and on various kinds of nucleation and crystal growth. The introduction of new growing methods allows the production of larger crystals. The growth of the needle-like crystals is governed by diffusion. The shape of the crystals does not differ qualitatively from their equilibrium shape. The crystals grow with smooth surfaces. Only the front surfaces show morphological imperfections, if the crystals exceed a critical size.     

Crystal Structure of a Rearranged Cage Compound, 3-Hydroxy-4-aza-8-oxoheptacyclo [9.4.1.0<Superscript>2,10</Superscript>.0<Superscript>3,14</Superscript>.0<Superscript>4,9</Superscript>.0<Superscript>9,13</Superscript>.0<Superscript>12,15</Superscript>]tetradecane

Abstract  Polycyclic hydrocarbon compounds exhibit a wide variety of biological activities, ranging from antiviral to Parkinson’s disease. Several structures such as the adamantanes have reached clinical status and are used therapeutically to treat, amongst others, neurodegenerative disorders such as Alzheimer’s. Polycyclics have also been utilised as carrier molecules to facilitate entry of drugs into the brain. The synthesis, molecular and crystal structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.0^2,10.0^3,14.0^4,9.0^9,13.0^12,15]tetradecane, are reported. NMR spectroscopy was applied for structure elucidation of the novel compound and a rearrangement mechanism is proposed for its formation. This compound crystallises in the orthorhombic system, space group Pbca (no. 61). The unit cell parameters are: a = 12.3763 (7), b = 11.6597 (6), c = 15.0539 (8) ?, V = 2172.3 (2) ?³ , and Z = 8 molecules in the unit cell. The reported structure was confirmed by X-ray analysis, which showed that the title molecules associate into centrosymmetric dimers via N–H···O hydrogen bonding. Index Abstract  The synthesis and structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.0^2,10.0^3,14.0^4,9.0^9,13.0^12,15]tetradecane, are reported in this article.      

SixGe1−xGaAs Heterojunction IMPATT-Diodes

Experimental research IMPATT-diodes on heterostructures Si_xGe_1−x-GaAs showed that the interphase boundary is noted with high thermal and radiation resistance. It is shown that such diodes are an equivalent alternative IMPATT-diodes with type of Schottky barrier.     

X-ray reflectivity studies of very thin films of silicon oxide and silicon oxide–silicon nitride stacked structures

Oxide/nitride/oxide films were deposited onto bare silicon substrates by low-pressure chemical vapor deposition (LPCVD) of silicon nitride and thermal oxidation. The X-ray reflectivity technique has been used to study the influence of the growth conditions and of different cleaning procedures of the silicon substrate on the structure and morphology of the deposited multilayers. The results revealed how, from an analysis of the X-ray reflectivity data performed by using Fresnel equations for multilayers modified to account for the interface imperfections, we determine, in a non-destructive manner, structural parameters such as density, thickness, roughness, and interface structure of the whole dielectric layers, giving us more information and greater sensitivity respect to cross-section transmission electron microscopy (TEM) and ellipsometric measurements.     

Real Structure of LiB3O5 (LBO) Crystals Grown in Li2O‐B2O3‐MoO3 System

The liquidus surface structure and field of LiB₃O₅ (LBO) primary crystallization have been revealed in Li₂O‐B₂O₃ ‐MoO₃ ternary system. The optimization of charge composition and growth conditions results in large volume optical quality LBO single crystals yielding. Crystallographic properties and real defect structure of grown LBO single crystals have been investigated by X‐ray powder diffraction method and X‐ray reflection topography. The volume of the crystals is partly free of any structural imperfections.     

Application of mean‐separation‐works method to protein crystal nucleation

Using mean‐separation‐works method of Stranski and Kaischew calculations of nucleus form and energy barrier for its formation are performed for globular protein crystals. This is done on the basis of a simple model suggested for crystal nucleation of such proteins. The prerequisite for the model is the fact that strict selection of definite sticky patches on protein molecule surface is obligatory for forming crystal lattices. The calculation results are in agreement with experimental data. (© 2008 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X-ray diffraction study of (TlInSe<Subscript>2</Subscript>)<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>(TlGaTe<Subscript>2</Subscript>)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> crystal system

The crystallographic and dynamic characteristics of TlInSe₂ and TlGaTe₂ crystals have been studied by X-ray diffraction in the temperature range of 85–320 K. The temperature dependences of the unit-cell parameters a of TlInSe₂ and TlGaTe₂ crystals, as well as their coefficients of thermal expansion along the [100] direction, are determined. The concentration dependences of the unit-cell parameters a and c for (TlInSe₂)_{1 − x} (TlGaTe₂) _x crystals are measured. Anomalies are found in the temperature dependences of the unit-cell parameters a and, correspondingly, the coefficient of thermal expansion, indicating the existence of phase transitions in TlInSe₂ and TlGaTe₂ crystals.     

Structural,ferroelectric and magnetic properties of Bi0.85Sm0.15FeO3 perovskite

Room temperature crystal structure, ferroelectric and magnetic properties of polycrystalline Bi_0.85Sm_0.15FeO₃ samples were investigated. X‐ray diffraction study shows that the compound possesses a dominant PbZrO₃‐like orthorhombic structure with √2a ×2√2a ×2a superlattice (a is the parameter of the cubic perovskite subcell). In contrast to piezoresponse force microscopy data demonstrating some features characteristic of ferroelectrics, polarization vs. electric field measurements reveal the behavior expected for nonpolar materials. Investigation of magnetic properties confirms that 15% samarium substitution suppresses the spin modulation typical of BiFeO₃ and induces the appearance of spontaneous magnetization. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of N-methyl Crotananinium Iodide — A Pyrrolizidine Alkaloid

The crystal structure of N-methyl crotananinium iodide has been determined by X-ray structure analysis. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ with cell parameters a = 19.37(2), b = 7.70(2), c = 13.38(2) Å. The structure has been solved by Patterson and successive Fourier methods and refined by full matrix least-squares methods to an R-index of 0.075. The structural features of the title compound are noted and are compared with those of similar others of such pyrrolizidine alkaloids.     

Chemistry of organic eutectics: Phenanthrene — benzoic acid and phenanthrene — cinnamic acid systems

Solid-liquid equilibrium data for binary systems of phenanthrene with benzoic acid and cinnamic acid, expressed in the form of temperature-composition curves, show the formation of a simple eutectic in each case. Linear velocity of crystallisation (v), studied by capillary method at different undercoolings (ΔT), suggests the applicability of Hillig-Turnbull equation, v = u(ΔT) ⁿ, where u and n are constants depending on the nature of solidification. Data on heats of fusion of pure components and eutectics, determined by the DTA method, infer appreciable interaction among the components in the eutectic melts. To highlight the nature of interactions among the components forming the eutectic melt, the excess thermodynamic functions such as h^E, s^E, and g^E were computed. Microscopic studies reveal that the structure of eutectic is different from those of the parent components. Infrared spectra, recorded in the region, 4000 —625 cm⁻¹, indicate weak interactions among the components in the eutectic.     

Structural Features of <Emphasis Type="Italic">Ortho</Emphasis>-hydroxy Bis-phenols and Their Comparison with <Emphasis Type="Italic">Para</Emphasis>-hydroxy Bis-phenols

Abstract The crystal structures of four bis-phenols are reported to substantiate the fact that the weak interactions play a major role in the crystal packing of bis-phenols. The reaction of 2,4-dimethylphenol with aldehydes such as 2-naphthaldehyde, terephthaldehyde in the presence of trifluoracetic acid gave 2-[bis(2-hydroxy 3,5-dimethylphenyl)methyl]naphthalene (1) and 4-[bis(2-hydroxy 3,5-dimethylphenyl) methyl]benzaldehyde (2), respectively. The 2-[bis-(2-hydroxy 3,5-dimethylphenyl)-methyl]naphthalene (1) crystallizes in orthorhombic, Pbca, a = 11.905(3) ?, b = 18.788(5) ?, c = 18.894(5) ?, 4-[bis(2-hydroxy 3,5-dimethylphenyl)methyl] benzaldehyde (2) in monoclinic, Cc, a = 8.880(3) ?, b = 16.394(7) ?, c = 13.700(5) ?, γ = 104.542(2)°. The reaction of 2-nitrobenzaldehyde with 2,4-dimethylphenol gave 2-benzo[c] isoxazo-3-yl 4,6-dimethylphenol (3) and its crystal parameters are orthorhombic, P2₁2₁2₁, a = 7.737(6) ?, b = 11.885(9) ?, c = 13.336(8) ?. The reaction of 2,6-dimethylphenol with 4-nitrobenzaldehyde and 2-chlorobenzaldehyde gave bis(4-hydroxy 3,5-dimethylphenyl)(4-nitrophenyl)methane (4) and bis(4-hydroxy 3,5-dimethylphenyl)(2-chlorophenyl)methane (5), respectively. The bis(4-hydroxy 3,5dimethylphenyl)(4-nitrophenyl)methane (4) crystallizes in monoclinic, C2/c, a = 25.921(1) ?, b = 12.202(4) ?, c = 15.6084(7) ?, β = 122.172(4)°, and bis(4-hydroxy 3,5-dimethylphenyl) (2-chlorophenyl)methane crystallizes as acetonitrile solvate (5) in triclinic, P-1, a = 12.314(3) ?, b = 14.111(3) ?, c = 15.078(5) ?, α = 98.268(2)°, β = 111.268(2)°, γ = 114.304(1)˚. The unit cell of 5 contains two pairs of crystallographically unsymmetric molecules of bis-phenols. Index abstract The crystal structures of four bis-phenols are reported to substantiate the fact that the weak interactions plays a major role in crystal packing and can induce symmetry non-equivalence among bis-phenols in unit cell of bis-phenols.