bluuebunny/crossref_metadata_2025 huggingface dataset:
Dislocation etching of tin iodide single crystals
Authors: Desai C. C. , Rai J. L.
Published: January 2007

Single crystals of tin‐iodide (SnI2) have been grown using the controlled reaction between SnCl2 and KI by diffusion process in gel medium. As grown (010) surfaces of the crystals have been optically studied. Characteristic etch pits have been observed on them. This suggests that SnI2 crystals might go into dissolution in the acid‐set gel. By successively etching (010) surfaces in a mixture of ammonia, acetic acid, and CdCl2 solution, it is established that the pits indicate the site of dislocations in the crystals. This is further confirmed by comparing the etch patterns before and after chemically polishing (010) surfaces. The average dislocation density in the crystals have been evaluated and found to be 3.2 × 103 cm−2 and the implications are discussed.
On the estimation of X‐ray extinction changes due to randomly distributed dislocations in crystals
Authors: Klimanek P. , Hanisch K.‐H.
Published: January 2007

A procedure proposed by Ivanov, Klimanek and Skakov for the quantitative estimation of X‐ray extinction in crystals containing randomly distributed dislocations is established without restriction concerning the defect density on the basis of stochastic geometry. The dependence of the extinction coefficient of a X‐ray diffraction peak obtained in this way agrees very well with experimental observations.
Plastic bend in a growing crystal
Authors: Eidelman L. G.
Published: January 2007

In case of nonlinear axial temperature distribution the relaxation of thermoelastic stresses results in the plastic bend of the growing crystal, i. e. in the generation of a residual lattice curvature equal to ϱ b. Based on results from Billig and from Indenbom the author presents estimations of dislocation densities (ϱ) (i. e. residual lattice curvature) taking into account an elastic limit differing from zero. It is shown that sign and value of the residual lattice curvature may be effectively used as criteria pointing out how thermal conditions should be changed for abtaining more perfect crystals. This approach application allowed to grow larger KCl single crystals (300 mm in diameter more than 100 kg by weight) with better structure perfection (specific subboundaries surface 2—3 cm2/cm3, mean subgrain dimension 0.6—1 cm, mean mutual disorientation of subgrains of not more than 6′).
Doping mechanism and properties of Zn‐doped GaN‐epitaxial layers
Authors: Andreev V. M. , Petrov M. N. , Pichugin I. G.
Published: January 2007

The role of oxygen in the process of doping GaN by Zn is established. It is shown theoretically and experimentally that Zn is dissolved in GaN in the form of complexes ZnO when oxygen or water vapour is present in the ambient of the growth reactor. Most of the complexes are neutral. Only the small part of Zn introduced is situated in electrically active positions. This fact can explain the enormously high Zn concentration which is necessary to obtain the compensation of GaN native donors.

The electrical and luminescence properties of GaN epitaxial layers doped by Zn are given and the relation of these properties to the growth and doping conditions are considered.
Iso‐epitaxial growth of n‐octacosane crystals
Authors: Prasad P. B. V. , Raju I. V. K. Bhagavan
Published: January 2007

Iso‐epitaxial(epilayer)growth of n‐octacosane crystals is reported. The morphology of the epilayers is in the form of triangular growth islands with or without truncature. Epilayer growth precedes spiral growth mechanism which occurs at medium and low supersaturations, respectively. The occurrence of triangular and truncated rhombic platelets is found to be a manifestation of growth at medium supersaturations.
Investigations on binary p‐nitrophenol and trichloroacetic acid eutectic system
Authors: Sharma B. L. , Sharma N. K. , Bassi P. S.
Published: January 2007

p‐Nitrophenol and trichloroacetic acid eutectic system has been investigated using phase‐diagram, undercooling, linear velocity of crystallization and viscosity measurement methods. Microstructure of the eutectic indicates that it possesses faceted‐faceted (f/f) morphology. Phase equilibrium data have been subjected to thermodynamic analysis, and GE and SE values for each mixture as a function of composition and temperature have been determined. Thermodynamic analysis shows that the system is non‐ideal.
Electrical properties of AgGaSe2 epitaxial layers
Authors: Neumann H. , Nowak E. , Schumann B. , Kühn G.
Published: January 2007

Epitaxial layers of AgGaSe2 with thicknesses in the range from 50 to 70 nm were deposited onto (111)A‐oriented semi‐insulating GaAs substrates by flash‐evaporation in the substrate temperature range TS = 825 … 900 K. Films grown at TS ≦ 850 K are n‐type conducting whereas p‐type conductivity was observed at TS ≧ 875 K. In the p‐type samples two acceptor states with ionization energies of 60 and 410 meV were found from an analysis of the electrical measurements.
The effect of temperature on the kinetics of scale growth
Authors: Veverka František , Söhnel Otakar , Hlaváč Michal
Published: January 2007

The temperature dependence of the kinetics of incrustations growth on heat‐exchange surfaces from solutions of NH4NO3 was examined. With increasing temperature the formal kinetic exponent of growth is decreasing and the kinetic constant of growth is increasing. The linear rate of growth of NH4NO3 incrustations is increasing with rising temperature within the whole range of measured supersaturations.
Dielectric investigations in liquid crystalline substances with elongated lateral groups
Authors: Kresse H. , Keil M. , Weissflog W.
Published: January 2007

By the aid of dielectric measurements (dipole moments, static dielectric constants, dielectric absorption) the influence of the chemical structure of a lateral group on the dielectric behaviour has been investigated. From the experimental data can be deduced that the lateral group rotates independently.
A note on the mechanics of diffusion of defects in solids
Authors: Michel B. , Michael D.
Published: January 2007

This paper deals with diffusion of point defects due to lattice deformations around the defects. The continuum theory of lattice defects is applied to derive suitable diffusion equations taking into consideration the fields of self‐stresses caused by the drift of defects. The model is applied to defects near surfaces and interfaces. The interesting phenomenon of “near‐surface Cottrell atmospheres” is discussed. The authors show that Cahns theory of spinodal decomposition is included in the model as a special case.
On batch homogeneity in horizontal CVD reactors (II). HCl gas‐phase etching
Authors: Richter F. , Morgenstern Th. , Sperling R.
Published: January 2007

A general model of the depletion is given, to which the reactive component of the reaction gas mixture in a horizontal CVD‐reactor is subjected during its flow along the heater. Furthermore the model of heating the process gas, described in Part I of this work, is used to derive an expression of the dependence of the thickness δ of the boundary layer upon the x‐coordinate (direction of the flow). Both models are combined to get a model of longitudinal homogeneity of wafer processing in an CVD‐reactor, which is applied to the special case of HCl gas phase etching. The predictions derived using the model were compared with experimental results.
Modelling crystal growth rate of barium chromate precipitated from homogeneous solution
Authors: De Silva R. L. , Creasy D. E.
Published: January 2007

An empirical power law type model, used for modelling crystal growth rate of barium chromate, when precipitation was carried out from homogeneous solution, has been applied to the re‐analysis of experimental data, based on which an unusual inverse size dependence on growth rate had been claimed previously. It is shown that the current empirical model provides a more realistic explanation of the data. The weaknesses of the previous approach are discussed in comparison with this new model.
Mathematical modelling and optimization of a molten phase crystallizing process
Authors: Bezegh A. , Domokos L. , Gàl S.
Published: January 2007

A mathematical model of a new process has been developed. A two‐dimensional function of a particle population density was defined on the phase space of mass and enthalpy. The basis of the model is the description of this density function at different stages of the process. The collision of particles followed by a coalescence is the sink and source of the particles. These events are related to the state of the total system and to the position of the particle in the phase space, and are proportional to particle density, particle cross section, particle velocity differences and residence time of particles. A computer program was written for calculations and for finding an optimum to the parameters of the process. The computations were carried out using the data for sorbitol crystallization.
Growth of n‐octacosane crystals from completely and partially stereo irregular solvents
Authors: Prasad P. B. V. , Raju I. V. K. Bhagavan
Published: January 2007

The growth of n‐alkane crystals from completely and partially stereo irregular solvents is reported. A sharp rise in the frequency of occurrence of simple and complex (interlaced) spirals is observed as the solvent characteristic changes from complete to partial stereo irregularity of the molecular chain. These observations are interpreted taking into consideration the acceptability of the solvent molecules as impurity in the growing crystal.
Influence of substrate orientation on the electrical properties of CuInSe2 epitaxial layers on GaAs substrates
Authors: Neumann H. , Nowak E.
Published: January 2007

The electrical properties of CuInSe2 epitaxial layers on (111)A‐, (110)‐, and (100)‐oriented GaAs substrates are investigated. At substrate temperatures Tsub ≧ 820 K the p‐type conductivity observed is governed by an acceptor state with an ionization energy of about 110 meV independent of the substrate orientation. At Tsub ≦ 770 K three different acceptor states are found in dependence on the substrate orientation: 390 meV for (111)A‐, 110 meV for (110)‐, and a very shallow acceptor for (100)‐oriented substrates. A possible correlation between these acceptor states and intrinsic defects is proposed.
Structural changes in MgO by activation in a planetary mill
Authors: Steinike U. , Kretzschmar U. , Tolochko B.
Published: January 2007

Mechanical activation of MgO in a planetary mill results in structural changes comparable to those observed in a vibration mill. Under the given conditions they are, however, achieved in considerable less time. Furthermore, a so far unreported lattice dilatation could be observed. The activated MgO showed an increased reactivity with respect to the ambient atmosphere. As a result magnesium hydroxide and a basic magnesium carbonate are formed.
Numerical calculation of marangoni convection in a rectangular open boat
Authors: Wilke H. , Löser W.
Published: January 2007

Numerical calculations of the flow caused by thermocapillary forces at the free surface in NaNO3 and Si melts in an open boat geometry have been carried out. The results agree well with measured flow velocities in model experiments for crystal growth configurations with NaNO3 melts. For Si melts a transition to a more complicated multiple eddy flow occurs. The projection‐iteration method used for the calculations is much more effective than the finite difference methods applied until now and is especially advantageous for more complicated flow patterns.
The dependence of surface morphology of GaSb‐ and AlxGa1–xSb epitaxial layers on the conditions of LPE growth
Authors: Yordanova I. M. , Pramatarova L. D.
Published: January 2007

The present work shows the dependence of surface morphology of the GaSb and AlxGa1–xSb epitaxial layers on the conditions of LPE growth. It is found that for LPE growth at 500 °C a supersaturation of 5—10 °C and a cooling rate of 0.24—0.4°C/min for GaSb epitaxial layers and 0.8—1.2 °C/min for AlxGa1–xSb epitaxial layers is necessary to obtain a flat and smooth surface.
Instability of “slow” solid‐liquid interface relaxation before the hetero‐LPE of III‐V compounds
Authors: Bolkhovityanov Yu. B. , Chikichev S. I.
Published: January 2007

Results of specially designed experiments supplemented by numerous literature examples have been analysed in attempt to elucidate the processes occurring at the interface between saturated multicomponent liquid and a non‐equilibrium solid before the hetero‐LPE of nearly lattice‐matched III–V compounds. The “slow” interface relaxation which provides the moving of non‐equilibrium solid‐liquid system in the direction of thermodynamic equilibrium by solid‐state diffusion (and which was previously believed to be the only way of equilibrium approach in lattice‐matched systems) looses the stability in some cases, being replaced by “fast” relaxation. It has been shown that the liquid‐solid interface instability develops due to a collective action of several factors, and their particular combination produces definite mode of relaxation. The “slow” relaxation would be unstable, if, as a result of underlying solid dissolution: (1) the lattice parameter of equilibrium solid decreases continuously with respect to that of the substrate, increasing thereby the driving force for dissolution; (II) the solubility of group V component in a changed liquid increases. In a majority of cases the switching to “fast” relaxation is facilitated by (III) the initial negative difference between the lattice parameters of equilibrium and underlying solids at the growth temperature.
Reciprocal crystal and P.B.C.‐vector method. Crystal growth of a‐sulphur
Authors: Follner H.
Published: January 2007

The morphological lattice of α‐sulphur (F ddd) has coordinates 1/8, 1/8, 0. The reciprocal crystal is a polyhedron with 15 faces and point symmetry 112. The arrangements of the polyhedra parallel to the crystal faces confirm that (100), (101), (010), (011), (111), (113), (001) are F‐faces and (110), (112) S‐faces according to Hartman and Perdok. Under consideration of the extinction rules of the morphological lattice (101) and (011) have to be regarded as S‐faces. The size of the polyhedra faces is proportional to the interaction energy given by Hartman. It will be shown that the face area of the net planes, divided by the number of molecules per growth layer, represent a good approximation to the attachment energy calculated according to Hartman. The average deviation for α‐sulphur is 3%, for olivine and SnJ4 8.5% and for anthracene 10.5%. The Wulff‐plots correspond fully to the experimental observations.
Influence of source composition on the properties of flash‐evaporated thin films in the Cu–In–Se system
Authors: Neumann H. , Schumann B. , Nowak E. , Tempel A. , Kühn G.
Published: January 2007

Using CuIn2Se3.5 as source material epitaxial layers are obtained on (111)A‐ und (100)‐oriented GaAs substrates by flash evaporation in the substrate temperature range Tsub = 720—870 K. The composition of the films is between CuInSe2 and CuIn2Se3.5. The structural properties of the films are similar to those for CuInSe2 epitaxial layers and refer to a chalcopyrite‐like structure. The films are always p‐type conducting but different acceptor states are found in dependence on the substrate temperature.
Discontinuous Freedericksz transition in the smectic C phase
Authors: Schiller P. , Pelzl G.
Published: January 2007

The threshold field of the Freedericksz transition in planar oriented SC monocrystals possessing positive dielectric anisotropy is calculated for two boundary conditions. It is shown that the threshold field is relatively low when a discontinuous transition is taken into consideration. The effective elastic constant is determined from the experimental data.
Influence of crystallization conditions on the size of cellular and cellular‐dendritic substructure
Authors: Esin V. O. , Vorontsov V. B.
Published: January 2007

A relationship is shown to exist between the size of the cellular‐dendritic substructure and the growth conditions. The dependence of the cell diameter on the crystallization rate is non‐monotonic, having a maximum in the region of low solidification rates. Theoretical calculations are compared with experimental data.
Metastable zone width in salting‐out crystallization
Authors: Karpinski Piotr H. , Nývlt Jaroslav
Published: January 2007

Measurements of the metastable zone width, giving information on nucleation characteristics, have been used for crystallization by cooling until now. This approach is now adopted for salting‐out of inorganic salts from aqueous solutions by addition of an organic solvent. Theoretical description is illustrated by precipitation of magnesium sulphate using methanol and ethanol as second solvents.
A new method of site occupancy analysis in substitutional mixed crystals by means of X‐ray crystal structure analysis (I). Pseudo lattice and superposition structure of a substitutional mixed crystal
Authors: Zedler A.
Published: January 2007

In Part I the nature of disorder in mixed crystal structures will be discussed on the basis of a pseudo lattice concept. A mixed crystal pseudo lattice applicable to all atomic positions of these mixed crystal structures will be defined, and the concept of a statistically globaldisordered ideal structure will be introduced. The structure factor for mixed crystal structures will be derived in consideration of the statistic disorder of position and sort of the atoms. The interpretation of the mixed crystal structure as a superposition structure requires the replacement of Vegard's rule by a new one having a wider range of validity.
On the substructure of epitaxial (Pb, Sn)Te films grown on KCl cleavage faces
Authors: Schenk M. , Tap Ngo Dien
Published: January 2007

The X‐ray diffraction rocking curve analysis has been employed for the measurement of crystallite sizes of (Pb, Sn)Te films for different thickness, epitaxially grown on KCl cleavage faces by the hot‐wall technique. The size of the coherently scattering regions parallel to the reflecting planes did not depend on film thickness and agreed with the mean distance of nuclei just before coalescence, investigated by means of replica electron microscopy. The results are consistent with a model of stalk‐like growth of crystallites in film growth direction.
The crystal structure of butylammonium dodecylsulfate
Authors: Szulzewsky K. , Schulz B. , Vollhardt D.
Published: January 2007

C16H37NO4S, monoclinic, P 21/m, a = 25.398(11), b = 7.366(4), c = 5.459(3) Å, β = = 91.53(4)°, Z = 2, V = 1020.91 Å3, Dx = 1.104 g/cm3, μ(MoKα) = 0.175 mm−1, λ(MoKα) = 0.71069 Å. The crystal structure of this anionic surfactant was solved by Patterson methods and refined to R = 0.109 for 2497 reflections. Dodecyl‐ and butylchains are statistically disordered. Loose package of butyl chains enables strong vibration motions. The polar region satisfies the mirror plane which is by the remaining structure parts only statistically fulfilled. Statistical disorder was included in the structure refinement by separation of some atom positions. The sublattice of the hydrocarbon chains is nearly O⟂ with as = 4.77, bs = 7.37, cs = 2.52 Å.
Temperature dependence of the X‐ray diffuse scattering intensity in V3Si in the temperature range from 8 to 300 K
Authors: Sirota N. N. , Polutchankina L. P. , Orlova N. S.
Published: January 2007

Measurements of the diffuse X‐ray scattering are performed from the (110) plane in V3Si single crystal at different temperatures from 300 to 8 K. Contours of equal diffuse scattering intensity are drawn over the 440 node in the (001) and (111) sections. The temperature dependence and the anisotropy of the thermal diffuse scattering intensity distribution for this compound are analysed.
Low ohmic multilayer contacts in lead‐Tin‐Telluride diode lasers
Authors: Herrmann Ka. , Sumpf B. , Böhme D. , Hannemann M.
Published: January 2007

The preparation and the influence of low ohmic multilayer thin film contacts of lead‐salt homo‐ and heterolasers on the degradation of lasing parameters during recycling processes between low working temperatures and room temperatures storage are described and discussed in detail.
Dendritic growth forms of borax crystals
Authors: Takoo R. K. , Joshi M. S. , Patel B. R.
Published: January 2007

A variety of dendritic forms of borax grown from solutions by the film formation method is given. The changing growth morphology is followed as a function of concentration and temperature. The initial, intermediate and final growth morphologies are described and discussed. Influence of evaporation rate and supersaturation on the mechanism of growth is assessed. It is suggested that under all crystallization conditions, borax crystals have dendritic form in the initial stages of growth.
Stoichiometry and point defects in lithium niobate crystals
Authors: Bollmann W.
Published: January 2007

Investigations of the OH− ion incorporation into LiNbO3 crystals and the comparison of calculated and measured densities show that undoped congruent lithium niobate crystals contain Li+ and O− − ion vavancies O and Li+. If really present, stacking faults are of inferior importance. The good agreement of the absorption edges of stoichiometric and of 2.7 mol% MgO containing congruent lithium niobate crystals is explained by the occupance of all oxygen sites within these crystals.
Mode of solidification and strength properties(II). Naphthalene‐benzil binary system
Authors: Bassi P. S. , Sharma N. K. , Sharma M. K.
Published: January 2007

The tensile and compressive strengths of directionally and randomly grown samples of naphthalene, benzil, and their eutectic in the faceted‐faceted benzil‐naphthalene system have been determined. The tensile strength of naphthalene and the eutectic increased significantly on directional solidification. Directional solidification substantially enhanced the compressive strength of the eutetic whes rea decrease in compressiv strength was observed in case of directionally grown naphthalene. In case of benzil, no appreciable change in strength was observed on directional solidification. A comparison between the tensile and compressive strength was made. The compressive strength was 2.5–3.8 times more than the tensile strength of naphthalene, grown randomly, benzil and their eutectic grown randomly and directionally.
Crystal and molecular structure of bis[2‐ethylamino‐4‐n‐propylamino‐6‐methoxy‐1,3,5‐triazine] copper(II) dichloride. 2‐Ethylamino‐4‐n‐propylamino‐6‐methoxy‐1,3,5‐triazine
Authors: Reck G. , Bannier G. , Kircheiss A. , Bauwe R.
Published: January 2007

The title compound crystallizes in the triclinic space group P1 with 2 formula units C27H51Cl2CuN15O3 in the unit cell. The lattice constants are a = 11.298(2), b = 16.024(4), c = 11.977(3) Å, α = 111.64(2), β = 102.59(2), and γ = 94.46(2)°. The crystal structure was determined by the conventional R = 0.147. The complex formation and the conformations of the three independent triazine molecules are discussed.
Ionicity of the chemical bond in AIBIIIC semiconductors
Authors: Neumann H.
Published: January 2007

The Phillips — van Vechten dielectric theory for binary tetrahedral compounds and Levine's extension of this theory to multibond crystals is used to evaluate the bond ionicities in the AIBIIIC chalcopyrite compounds with AI = Cu, Ag from spectroscopic data. In deriving the ionicity of the AI—CVI bond the influence of the noble metal d electrons it taken into account. The results obtained are compared with previous estimations.
Synthesis of analcime‐type zeolite from natural stilbite by hydrothermal method
Authors: Joshi M. S. , Choudhari A. L. , Kanitkar Ravindra
Published: January 2007

Using calcined stilbite, aluminium hydroxide and sodium hydroxide as ingradients, the procedure to synthesize a zeolite by hydrothermal method is described. Studies on characterisation (of crystals grown) by X‐rays and by infrared spectroscopy, and their morphology by a scanning electron microscope are reported. That the crystals grown have cubic symmetry with a = 13.66 Å and that they are analcime type is established. From infrared spectral studies it is confirmed that the crystals are zeolites. Needle, prismatic, and layer crystals obtained are illustrated and described.
The precipitation of barium hydroxoaluminate hydrate powders from sodium hydroxoaluminate solutions: Precipitate phases and precipitation mechanisms
Authors: Packter A.
Published: January 2007

Barium hydroxoaluminate hydrates were precipitated from different sodium hydroxoaluminate solutions at 20 °C; CAl varied from 0.1 to 0.5 M and initial Ba/Al2 ratios ( = excess OH/Al ratios) varied from 1 to 7. Precipitate compositions were determined by chemical analysis, infra‐red spectrophotometry and thermal analysis. The compound BaO · Al2O3 · 7 H2O was precipitated at initial Ba/Al2 ratios of one to well above two while the compound 2 BaO · Al2O3 · 5 H2O was only precipitated over a narrow range of concentrations. The compound Ba(OH)2 · 8 H2O was precipitated from solutions of high hydroxide and barium ion concentrations. The ionic equilibria and precipitation mechanisms in different solutions are discussed.
X‐ray investigation of H2‐annealed quartz crystals
Authors: Zaumseil P.
Published: January 2007

This paper investigates the variation of reflection properties of nearly perfect quartz crystals after annealing in H2‐atmosphere. Annealing at 800 °C causes a strong distortion of the lattice structure. Double‐crystal diffractometer measurements show an approximate tenfold increase of the integral reflection coefficient. The reflection properties change homogeneously over the whole crystals.
Crystal and molecular structure of 3β‐hydroxy‐5β‐estr‐8(14)‐en‐17‐one
Authors: Reck G. , Schubert G. , Langbein G.
Published: January 2007

The title compound crystallizes in the orthorhombic space group P212121 with 4 formula units C18H26O2 in the unit cell. The lattice constants are a = 10.356(2) Å, b = 19.743(3) Å, and c = 7.487(1) Å. The structure was solved by direct methods of phases determination and refined by least‐squares calculations to the conventional R = 0.054.

The configuration and conformation of the molecule were determined and compared with those of Δ‐8,14‐anhydrodigitoxigenin.
On splitting of dislocations at a reverse motion in germanium single crystals
Authors: Bondarenko I. E. , Farber B. Ya. , Khodos I. I. , Nikitenko V. I.
Published: January 2007

The dislocation dissociation after the reverse motion along a slip plane in Ge single crystals have been investigated. It has been established that the dissociation width as well as the constriction density were independent on the motion direction. The results obtained have been used to clarify the role of the dislocation splitting in the formation of the phenomenon of the dislocation mobility asymmetry.
Structural and thermal properties of Zn2+‐, Cd2+‐, and Hg2+ forms of zeolite X
Authors: Zieliński S. , Sarbak Z.
Published: January 2007

The exchange of Zn2+, Cd2+ and Hg2+ with zeolite NaX has been studied. The influence of the above cations on crystalline structure of zeolite X and its thermal stability has been shown on the grounds of X‐ray diffraction, differential thermal analysis and infrared spectroscopic measurements.
Re‐determination of the temperature of the coherent spinodal curve in an‐Al‐15 at.% Zn alloy by transmission electron microscopic and hardness investigations
Authors: Kroggel R. , Dutkiewicz J.
Published: January 2007

The character of the coarsening of the concentration modulations is studied in an Al‐15 at. % Zn alloy applying TEM investigations (TEM micrographs and diffraction patterns) and hardness measurements in the temperature range from 40 °C to 130 °C. From the TEM investigations the temperature of the coherent spinodal curve is estimated to be (93 ± 7)°C. This value agrees fairly well with the result obtained by means of hardness measurements (kink in the TTT‐curve occurring at about (84 ± 3) °C). The TEM observations of structure revealed in the Ta‐range below the coherent spinodal a periodic structure relevant to spinodal decomposition. The periodicity of modulations is confirmed by electron diffraction patterns where a clear effect of sidebands near the matrix spots is observed.
Spectroscopic analysis of the heat of formation in AIBIIIC compounds
Authors: Neumann H.
Published: January 2007

The spectroscopic model for the heat of formation of tetrahedrally coordinated binary compounds is extended to the ternary chalcopyrite semiconductors. The heats of formation of all AIBIIIC compounds are evaluated and compared with experimental data. Possible reasons for existing discrepancies between theory and experiment are discussed.
Studies on etching behaviour of {101} faces of natural mesolite crystals
Authors: Joshi M. S. , Joshi V. V. , Choudhari A. L. , Kanitkar R. G.
Published: January 2007

Etching behaviour of {101} habit faces of natural mesolite crystals is reported. Rectangular, truncated and elliptical etch pits are illustrated, and mechanism of their formation is assessed. Factors influencing kinetics of etching are discussed. From Arrhenius plots activation energy and pre‐exponential factor are computed and reported.
Ionic conductivity studies in KCl–NaCl mixed crystals
Authors: Veeresham P. , Rao U. V. Subba , Babu V. Hari
Published: January 2007

Single crystals of KCl and a few compositions of KCl‐NaCl mixed crystals were grown from melt by Kyropoulos technique. Ionic conductivity measurements have been carried in these crystals in the temperature range 100 to 400 °C. The activation energy for the migration of charge carriers have been calculated from the conductivity‐temperature plots of these crystals and the results obtained were discussed.
Thermoluminescence and optical absorption studies in γ‐irradiated KClxBr1–x mixed crystals
Authors: Veeresham P. , Reddy K. Narasimha , Rao U. V. Subba , Babu V. Hari
Published: January 2007

Thermoluminescence (TL) and optical absorption measurements have been carried in γ‐irradiated KCl, KBr and various compositions of KClxBr1–x mixed crystals as a function of irradiation time and composition. The position of the main glow peak (high temperature peak) and F‐band position are found to vary non‐linearly with composition, showing a correlation between colour centers and TL. The TL peaks have been analysed by numerical fitting and the trap depths and frequency factors have been calculated for different compositions of the mixed crystals. The thermal ionisation energy of F‐centers has been calculated for the mixed crystals and it is found to vary non‐linearly with composition. The results obtained in mixed crystals have been discussed in terms of high disorder present in them.
Phase fronts at the NaNbO3P‐⇌ NaNbO3 R phase transition
Authors: Dec J.
Published: January 2007

The structural phase transition between phase P and phase R in NaNbO3 single crystals was studied by an optical method. It was found that this transition is similar to the martensitic transformation and that the phase fronts are formed by crystallographic planes having indices close to {0.2.11}. Behind the simple phase front a monodomain state arises. The polydomain state is the resultant of complex phase fronts.
Growth, intensity and probabilities of f‐f transitions of Nd3+ ions in KNd(PO3)4 single crystals
Authors: Mazurak Z. , Jeżowska‐Trzebiatkowska B. , Schultze D. , Waligora C.
Published: January 2007

From a study of the melting diagram KPO3—KNdP4O12 optimum conditions are derived for the growth of KNd(PO3)4 single crystals by the flux method. The absorption spectrum of KNd(PO3)4 was measured between 320 and 1000 nm at room temperature. The three JUDD‐OFELT parameters Ωλ were determined by numcerical methods and compared to the data for NdP5O14. A correlation has been attempted between the Ω2 parameter and the site symmetry of Nd3+ in Nd‐containing laser crystals. The calculated fluorescence branching coefficients from the 4F3/2 level are in good agreement with the epxerimental data.
Structure of fault stackings of molecular layers X—M—X in CdI2 polytypic crystals
Authors: Pałosz B. , Przedmojski J.
Published: January 2007

The arrangements of molecular layers I—Cd—I, which may be regarded as “faulted” for CdI2 polytypic crystals, are analyzed. Tentative classification of faults into those which are intermediate structure between the basic polytypes 2H and 4H and faults occurring between different blocks of pure structure 4H is proposed. The connection between some growth parameters and the structure of faults in CdI2 crystals grown from solutions is discussed. It is shown that the geometrical classification of stacking faults used for layered inorganic crystals is not appropriate for the description of the faults existing in polytypic crystals of MX2 type. The effect of weak external electric and magnetic fields on the polytypic structure of CdI2 is analyzed. The experiments performed for several hundred of polytypes of CdI2 showed that the external fields may, in some conditions, affect the organization of the polytypic structure of crystals very strongly. In particular, it was found that the external fields may change the period of polytype cells and that the relative number of hexagonal and rhombohedral polytypes differ very strongly for crystals grown in the absence and in the presence of external electric and magnetic fields.
X‐Ray study of the defect structure of PbTe single crystals
Authors: Berger H. , Mizera E. , Auleytner J.
Published: January 2007

PbTe single crystals grown by different methods were thinned electrolytically and examined by X‐ray transmission topography. The transmission topographs, first obtained of this material, reveal substructure, slip lines and single dislocations. The samples exhibit different structural perfection in dependence on the growth method. In crystals of relatively high perfection, slip lines are the striking feature of defect structure, caused by surface damage during mechanical preparation. The most perfect sample has a dislocation density of 102 to 2 ṁ 103 cm−2. No slip occurs, probably due to small dopant contents.
Thermotropic liquid crystalline compounds with lateral long‐chain substituents (II).: Synthesis and liquid crystalline properties of 1,4‐Bis [4‐substituted‐benzoyloxy]‐2‐n‐alkylbenzenes
Authors: Weissflog W. , Demus D.
Published: January 2007

We synthesized 102 new 1,4‐bis‐[4‐subst.‐benzoyloxy]‐2‐n‐alkylbenzenes of the general formula

magnified image

with R = alkyl, alkyloxy, alkanoyloxy, alkyloxycarbonyloxy and n = 0 to 16. Surprisingly all of the new compounds are liquid crystalline nematic. Thus it is proved that lateral long chain substituents are compatible with liquid crystalline properties.
Dielectric relaxation investigations of the isotropic and nematic phases of 4‐n‐Butyloxyphenyl‐4‐n‐hexylbenzoate (BOHB)
Authors: Kresse H. , Demus D. , Moscicki J. K. , Wrobel S.
Published: January 2007

Experimental values of the complex dielectric permittivity in a wide frequency range are analized for the isotropic and nematic phase of BOHB. The results are discussed from the point of view of different of molecular reorientation mechanisms which are related to the structure of the molecule. It can be concluded that the molecules in the nematic phase exhibit a stronger tendency to reorient as “rigid bodies”.
The comparative study of mosaic structure of ZnO crystals by γ‐ray diffraction and conoscopic methods
Authors: Loshmanov A. A. , Chernysheva M. A. , Trunov V. A. , Kurbakov A. I. , Shaldin Yu. V. , Sizova N. L. , Kuzmina I. P. , Regel V. R.
Published: January 2007

It has been carried out the investigation of the mosaic structure of ZnO crystals by two methods providing the information on mosaic structure and inner stresses (γ‐ray diffraction and conoscopic method). It has been observed a certain correlation between the results obtained by the two methods.
Influence of the graduated composition region on the properties of GaInAs epitaxial layers grown on GaAs substrates
Authors: Popov A. , Ivanov I.
Published: January 2007

The electrical properties of Ga1‐xInxAs layers (0 < x < 0.3) are investigated. The layers are grown on <111> oriented GaAs substrates. A transition layer is grown with an increasing indium content to decrease the mismatch of the lattice parameters of the substrate and the final layer. A special many‐section crucible is used. In dependence on composition the decrease both of mobility and carrier concentration with the increase of compensation is observed. These facts are connected with the introducing of additional acceptors without donor concentration changes.
Correlation between different parameters of plastic deformation in doped NaCl crystals
Authors: Boyarskaya Yu. S. , Zhitaru R. P. , Linte M. A.
Published: January 2007

The yield stress (τy), the microhardness (H) and the dislocation mobility in the stress field of a concentrated load (γ) were measured in NaCl: Ca and NaCl: Pb single crystals within the temperature interval 77–673 K. It was shown that there was a good correlation between the concentration changes of τy, H and γ for NaCl:Ca crystals. Such clear results were absent for NaCl:Pb single crystals. An anomaly of τy at 77 K was revealed for these crystals; it was not followed by the H anomaly. In conclusion it was stated that the impurity hardening was connected with the increasing of dislocation mobility but such a parameter did not determine the temperature hardening.
Investigation on low temperature thermoluminescence centres in Quartz
Authors: Bernhardt Hj.
Published: January 2007

The present paper will help to understand the often investigated process of thermoluminescence of quartz which is of high complexity. A lot of traps exist in quartz crystals which compete with each other with respect to the trapping of charge carriers during the X‐ray treatment. That is why a variety of processes takes place after X‐irradiation at liquid nitrogen temperature (LNT) of quartz which complicate the phenomenology of low temperature thermoluminescence. This competition in the trapping process leads to the socalled “sensibilization” or “desensibilization” effects of thermoluminescence, respectively, which are described in this paper for the first time. This effect means the dependence of the LNT thermoluminescence intensity on a pre‐irradiation dose applied at room temperature (RT). The influence of this pre‐irradiation is understood assuming the saturation of competitive traps. This favours an enhanced trapping of charge carriers at LNT‐(shallow) traps instead of the preferential trapping on the deep traps in the case of X‐ray treatment of the as‐grown crystal at LNT. To get the afore mentioned model we take into account not only thermoluminescence but also coloration, ir‐ and vuv‐absorption measurements.
Chemical kinetics of dissolution of BaMoO4 crystals
Authors: Arora S. K. , Trivikrama Rao G. S. , Batra N. M.
Published: January 2007

An etchant capable of revealing the sites of dislocations in the flux‐grown crystals of BaMoO4 has been established. Using this etchant (HNO3), effect of etching time, acid concentration and temperature on the selective etch rate is demonstrated. It is established that the process of dissolution in unstirred HNO2 solutions is one of the diffusion rate controlled; an empirical equation governing the kinetics has been suggested.
Comparison of luminescence characteristics of Doped Molecular crystals grown by various methods
Authors: Kurnosov I. V. , Levitski I. A. , Naboikin Yu. V.
Published: January 2007

The effect of growth conditions on the line broadening in low temperature luminescence spectra of pyrene‐doped biphenyl single crystals in investigated. It has been shown that the crystals, grown by plate sublimation technique, possess the minimal linewidth. Various possible mechanisms of line broadening are discussed.
Auger electron spectroscopy studies of impurity effects on the hot deformability of AISI M2 high speed steel
Authors: Szilvásy Cs. , Menyhárd M. , Gergely G.
Published: January 2007

The effects of various materials parameters on hot deformability f of AISI M2 high speed steel are studied in a complex way. These studies revealed beside other parameters (e.g. carbides) a strong correlation between some impurities (S, Sn) and f, determined by hot deformability tests. The correlation between f and the P content prooved to be weaker. The paper is devoted to impurity effects. The composition and impurities of the samples and their isolated carbide phases have been determined by chemical analysis. In situ AES fractography and SEM were applied to study the fracture surfaces. The main results are: The S concentration of the fracture surfaces exhibits a correlation with the bulk content. Strong enrichment of S and P within a thin (1–3 nm) surface layer was revealed by AES in‐depth profiling, showing also carbide phases. In the temperature range ‐150°C — +250°C no grain boundary fracture was observed, fracture was ductile and void type. The fracture path is determined by carbides, being the sites of S and P enrichment.
Theoretical description of the external electroluminescence around a single dislocation oriented perpendicular to the surface
Authors: Pasemann L. , Hergert W.
Published: January 2007

Under the assumption that a dislocation decorated by impurities can be described as a macroscopic inhomogeneity the radial distribution of the flux of photons around a dislocation is calculated, where the internal absorption of the luminescence is taken into account in addition to the effect of the surface. The theoretical results are used to compute simulated images for different values of the radiative lifetime inside the dislocation region.
Dislocation generation around cylindrical pores
Authors: Friedrich E. , Boiko Ju. I. , Schatt W.
Published: January 2007

The formation of dislocation arrays reflecting the crystallographie symmetry of the surface pores formed by a mechanism of pitting corrosion was observed. The hypotheses developed in connection with the origination of dislocations around cylindrical pores by the effect of capillary forces led to process parameters whose estimated values agree well with those experimentally obtained. It is pointed to the importance of this process for the shrinkage during sintering.
Influence of lateral branches on the properties of liquid crystalline 1,4‐Bis‐[4‐n‐hexylbenzoyloxy]‐2‐subst.‐benzenes (II): connection between molecular structure and physical properties
Authors: Demus D. , Hauser A. , Selbmann Ch. , Weissflog W.
Published: January 2007

In 8 1,4‐bis‐[4‐n‐hexylbenzoyloxy]‐2‐subst.‐benzenes and one analogous hexylcyclohexanoyloxy compound the clearing temperatures, enthalpies, entropies, volumina and order parameters are considered with respect to the molecular structure and compared with predictions of molecular statistical theories. The results are in qualitative agreement with theoretical predictions and show the predominant role of the steric repulsive forces in stabilizing the nematic state.
Forest intersection of dislocations in HCP structures
Authors: Püschl W. , Schoeck G.
Published: January 2007

The contribution to flow stress by junction reactions in hep metals is computed using a virtual displacement method. Basal glide by 0°, 30°, 60° and 90° dislocations and trees with Burgers vector length a, c and |c + a| are considered. Conceptual shortcomings of previous treatments are discussed.
Precision measurements of plastic deformation of β‐CuZn at helium temperatures
Authors: Takeuchi S. , Hashimoto T. , Maeda K.
Published: January 2007

By attaching condenser plates directly to the tensile specimen, creep rates of β‐CuZn single crystals have been measured by the capacitance change in the strain‐rate range of 10−7to 10−5s−1and at temperatures between 0.7 and 17 K using a3He cryostat. Slope of the temperature variation of the stress to give a constant strain‐rate decreases below 5 K and seems to level off at 0 K. The strain‐rate sensitivity becomes almost constant below 2 K. The conventional activation analysis showed that an ARRHENIUStype strain‐rate equation breaks down drastically below 5 K. For an effective temperatureT*which gives 2 K at 0 K and asympototically coincides with the testing temperature at 5 K, the experimental results can be fitted to the ARRHENIUSstrain‐rate equation with an activation enthalpy ΔH(τ) for the PEIERLSmechanism. The above result is interpreted in terms of the quantum‐mechanical oscillation of the dislocations.
Deformation mechanism and dislocation structure of high‐purity molybdenum single crystals at low temperatures
Authors: Kaufmann H.‐J. , Luft A. , Schulze D.
Published: January 2007

High purity molybdenum single crystals were deformed in tension and compression along the symmetric double slip orientation [110] in the temperature range from 300 K down to 0.5 K with strain rates between 10−3 and 10−5 s−1. The activation volume was measured by stress relaxation tests. The dislocation structure of the deformed crystals (T → 1.85 K) was examined by high voltage electron microscopy. It was established that the low temperature increase of the critical shear stress exhibits three distinct temperature regimes with different temperature dependences. These non‐uniformities are discussed in terms of recently developed theories of kink‐pair formation and kink‐kink interactions on screw dislocations in bcc metals. The HVEM observations suggest that the mobility of screw dislocations at very low temperatures should be determined by the combined effects of the PEIERLS barriers and the jog dragging.
Slip band growth and dislocation velocities in thin flat crystals of n‐irradiated Cu and Cu‐30% Zn
Authors: Godon H. , Potthoff H.‐H. , Neuhäuser H.
Published: January 2007

Extending earlier work (POTTHOFF) the dependence of the arrangement and development of slip bands on the thickness of thin flat single crystals of neutron‐irradiated copper and Cu‐30% Zn orientated for singe glide is studied at room temperature. Distinct differences in the behaviour of thin (20 … 200 μm thickness) and thick (≧ 500 μm thickness) crystals are found. Partly they are connected with the bending stresses in the region of the Lüders band front. The velocities of dislocation groups in the first stages of slip band growth are estimated. The deformation kinetics is discussed in the concepts of viscous glide and nucleation rate of dislocations for both materials.
Strain history effects at low temperature deformation
Authors: Wielke B. , Mikulowski B.
Published: January 2007

The work hardening coefficient of hep metals like Zn or Cd depends on the temperature even at very low temperatures. Additional information of the processes involved can be derived from specially designed annealing experiments. If deformed single crystals of Zn, Zn + 0.2 at.% Ga and Zn + 0.2 at.% Ag are annealed the work hardening increases. The amount of increase depends on deformation temperature and annealing time. The effects observed suggest that the work hardening is determined at least partly by the mobility of points defects.
On the strengthening of Magnesium Single Crystals by Cadmium
Authors: Lukáč P.
Published: January 2007

Solid solution hardening in single crystals of magnesium containing cadmium (up to 2.4 at.%) has been investigated in the temperature range 77 K to 295 K. A strong temperature dependence of the critical resolved shear stress, τ0, is observed below 230 K, while above this temperature τ0 is temperature independent. At all temperatures τ0 is found to increase linearly with c2/3, where c is the concentration (in atomic fractions) of cadmium as solute. The concentration dependence of τ0 can be explained by the theory of LABUSCH.