bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Crucible Diameter and Sealing Pressure on Growth Features of As2Se3 Single Crystals
Authors: Kothiyal G. P. , Ghosh B.
Published: January 2007

Crystals of arsenic triselenide were grown in tubes of diameter varying from 14 to 25 mm sealed under partial pressure of Ar in the range 60–660 Torr. The temperature range of the growth zone was independent of crucible diameter and ambient pressure under otherwise identical conditions. A particular range of ambient pressure was conducive for the growth of good quality crystals and whiskers, growth rate increasing with diameter of tube. Transition to growth stage from nucleation stage was not spontaneous in tubes of diameter ≦ 16 mm but required a temperature cycling. Results are explained qualitatively.
Decanted Interface of Salol Crystals Grown from the Melt
Authors: Pan S. K. , Inoue T. , Komatsu H.
Published: January 2007

The decanted surfaces of a crystal grown from the melt show various kinds of solidification markings formed either during growth or decantation. Some of the special features which are peculiar to decantation were discriminated from the real solid‐liquid interface morphology by in situ observation of salol crystals under the microscope.
Formation of Pure Haematite by Hydrolysis of Iron (III) Salt Solutions under Hydrothermal Conditions
Authors: Voigt B. , Göbler A.
Published: January 2007

Comparing investigations were carried out of the hydrolysis of iron(III) sulfate, nitrate, and chloride under hydrothermal conditions with an aim to find a new way for the synthesis of pure α‐Fe2O3 (haematite). Rich yields of highly pure haematite can be precipitated from iron(III) nitrate solutions. The strong decrease of the impurity level in the hydrothermal formation of haematite permits to precipitate from impure technical solutions α‐Fe2O3 of adequate purity for many purposes.

In contrast, the precipitates from iron(III) sulfate or chloride solutions obtained under comparable conditions are rather uncomplete or the phases formed contain a more or less percentage of the respective anion.
Implications of the Euclidean Normalizers of Space Groups in Reciprocal Space
Authors: Koch E.
Published: January 2007

Each crystal structure with symmetry G exactly corresponds to i different but equivalent coordinate descriptions of the atomic arrangement and to i different but equivalent structure‐factor lists. The number i equals the index of G in its Euclidean normalizer NE(G). The isometries of one coset of G in NE(G) transform an original coordinate description and an original structure‐factor list into a certain other equivalent description and equivalent structure‐factor list. Two intermediate groups are uniquely defined: G ⫅ K(G) ⫅ L(G) ⫅ NE(G). G and K(G) are class‐equivalent whereas K(G) and NE(G) are translation‐equivalent. L(G) is the most comprehensive intermediate group from the same Laue class as G. In course of a structure determination with direct methods all information needed to “fix the origin” by appropriate restriction of some phases may be derived from the additional translations of K(G). If no anomalous scattering has been observed and if NE(G) is centrosymmetric but G is not, the positions of the inversion centers in L(G) determine the appropriate phase restriction to “fix the enantiomorph”.
Structures of the Triclinic and the Monoclinic Modification of Divascan®
Authors: Kuban R.‐J. , Szulzewsky K. , Kulpe S. , Schulz B.
Published: January 2007

Trielinic modification: C12N4O3H16.Mr = 264.26, triclinic P1,a= 7.702(3),b= 9.420(11),c= 10.893(8) A, α = 73.37(8), β = 82.22(5), γ = 66.30(6)°,V= 638(1) A3,Z= 2,Dm= 1.360 Mg m−3,Dx= 1.362 Mg m−3, λ(MoKα) = 0,71062 A, μ = 0.1084 mm−1,F(000) = 280,T= 296 K, finalR= 0.0742, wR= 0.0758 for 1842 reflections. Monoclinic modification: C12N4O3H16·, 3/2H2O,Mr= 291.28, monoclinic P 21,/c, α = 14.075(5),b= 12.631(6),c= 16.234(5) A, β = 99.25(3)°,V= 2849(1) A3,Z= 8,Dm= 1.338 Mg m−3,Dm= 1.359 Mg m−3, λ(MoKα) = 0.71062 A, μ = 0.1134 mm−1, F(000) = 1240,T= 296 K, finalR= 0.0557,wR= 0.0691 for 1266 reflections.

Comparison of the two independent Divascan® molecules of the monoclinic modification with the one of the triclinic modification demonstrates good agreement of related bond distances and angles in the molecules. Disorder of the hydroxyl groups of one Divascan® molecule of the monoclinic modification is announced by high vibration parameters of the related oxygen atom and a very short CO distance, which is not adequate to a real CO bond length.
Electron Microscope Observation of the ζ‐Mn5Ge2
Authors: Kifune K. , Komura Y.
Published: January 2007

The high‐temperature phase of ζ‐Mn5Ge2 has been studied by electron microscopy and electron diffraction. Alloy specimens contain two types of structures with different periodicities along their c direction; one is 3.9 nm and the other 1.3 nm. Domains of these two structures make parallel intergrowth with common α‐ and c axes. Results of the previous X‐ray structure analysis are explained by the mixture of the above two structures.
Ice‐Nucleation Activity of AgI Particles on the Surface of Water and into the Volume
Authors: Genadiev N. , Michailov M. , Nenow D.
Published: January 2007

The ice‐nucleation activity of AgI particles is investigated. The critical supercoolings are determined for water drops with particles situated on the drop surface and suspended into the drop volume. The ice‐nucleation activity of the AgI particles decreases with the gradually penetration of the particles into the volume. A large alteration (about 10 °C) for the mean freezing temperature is established. An attempt is made to explain this phenomenon with the lowering of the nucleation work on the three‐phase particle/water/water vapour contact.
Algorithm for the Transitional Portions during the CZ Crystal Growth Using a Computer Control
Authors: Satunkin G. A. , Rossolenko S. N. , Kurlov V. N. , Red'kin B. S. , Tatarchenko V. A. , Avrutik A. M. , Tuflin Yu. A.
Published: January 2007

A model is proposed for a non‐stationary process of diameter variation (growing out and narrowing) of the crystal, grown by the automated Czochralski technique, with the aim of obtaining the initial and final “cones” of any desired configuration. The calculations are illustrated by the experimentally grown lithium niobate crystals.
Interface Kinetical Limitations in Closed‐tube Chemical Vapour Transport (II). The CdTe:NH4Cl Growth System
Authors: Paorici C. , Pessina V. , Zecchina L. , Attolini G.
Published: January 2007

It has been shown that when CdTe erystal are grown by closed‐tube CVD, (HCl obtained from thermal decomposition of NH4Cl being the transport agent), large activational constraints occur which strongly limit the vapour phase mass transport.

The method is essentially based on a comparison between the semiempirically determined average diffusivity of the vapour phase during the growth process and corresponding diffusivity calculated assuming that kinetical limitation is absent.

The smaller (with respect to units) the ratio (ϕ) between the above defined diffusivities is, the larger the activational constraints are assumed to be.
Cadmium Incorporation in the Crystallization of Calcium Sulfate Hemihydrate from Phosphoric Acid
Authors: Tjioe T. T. , Van Woude H. Der , Verbiest J. , Durville P. F. M. , van Rosmalen G. M.
Published: January 2007

Semi‐batch crystallization experiments of CaSO4 · 1/2H2O(HH) were performed in concentrated phosphoric acid at various H2SO4 contents in the absence and presence of additives. The influence of the operating conditions and additives on the cadmium and phosphate incorporation in the HH lattice were determined. The Cd uptake increased with raising H2SO4 content. Addition of HNO3 caused a reduced cadmium and phosphate incorporation. Addition of iodide also lowered the cadmium incorporation.

The obtained results fits into a model for the incorporation of foreign ions during crystal growth. According to this model the incorporation is primarily a kinetically controlled process.
Determination of the Effective Kinetic Diameter of the Complex Molecules
Authors: Lilov S. K.
Published: January 2007

A method for the estimation of the effective kinetic diameter of the complex molecules is suggested. The method is based on the construction of a geometrical model by using the known data for the internuclear distances and atomic radii. On the basis of the suggested method the values of the effective kinetic diameter of some molecules for which there are no respective experimental data are calculated.
The Range of Metastable Formation and the Morphology of the Crystals in the System CaCO3–MnCO3
Authors: Franke W. , Hofer A.
Published: January 2007

Both slow precipitation, hydrogen carbonate transport at room temperature as well as hydrothermal decomposition of oxalates were used to grow mixed crystals in the system CaCO3–MnCO3. The limits of the immiscibility gap below 400 °C and the range of metastable formation at low temperatures were investigated Changes of the morphology of the crystals dependent on the temperature of formation and their composition are described.
Formation of a Special Intermediate during Phase Transformation of Zeolite NaA to Nepheline
Authors: Lutz Wolfgang , Fichtner‐Schmittler Helga , Richter‐Mendau Jürgen , Becker Gudrun , Bülow Martin
Published: January 2007

In the process of phase transformation of zeolite NaA to nepheline under hydrothermal conditions a special intermediate occurs. This is due to the high reaction rate of nepheline formation in the presence of water molecules. Consequently, the usually observed amorphous material with high condensed silica does not occur as separate phase. – The intermediate which is formed due to the destruction of the long‐range order of zeolite is significantly short‐range ordered. The phase transformation process starts at the outer surface of zeolite crystals, thus generating a diffusion barrier for sorption uptake processes.
Lattice Vibrations and Interatomic Forces in LiInS2
Authors: Sobotta H. , Neumann H. , Riede V. , Kühn G.
Published: January 2007

Infrared reflectivity spectra of LiInS2 are measured at room temperature in the wave‐number range from 180 to 4000 cm−1. The parameters of four optical modes are determined by a dispersion analysis of the spectra. From the interatomic force constants determined from the sphalerite‐like modes in the lattice vibration spectrum it follows that the Li–S bond is considerably weaker than the InS bond.
Microcomputer Programming of Temperature in a Batch Cooling Crystallizer
Authors: Jones A. G. , Akers S. R. G. , Budz J.
Published: January 2007

A new highly flexible batch crystallizer control system and suite of software using a BBC model B microcomputer to programme the cooling rate and log data is described. The programs were tested satisfactorily with the cooling crystallization of potassium sulphate solutions. Both linear and controlled cooling increased the mean crystal size with lower coefficient of variation compared to natural cooling crystallization with a consequent improvement in filtrability characteristics.
The Coprecipitation of Magnesium Iron (III) Hydroxide Powders from Aqueous Solution: Precipitate Compositions and Coprecipitation and Ageing Mechanisms
Authors: Packter A. , Derry A.
Published: January 2007

Series of magnesium iron(111) hydroxides were coprecipitated at ambient temperature from different mixed metal cation solutions, at CM tot = 0.1 M and Mg/Fe2 ratios from 4 to 1/4, with sodium hydroxide solution. The relevant single precipitations and the coprecipitations were monitored by potentiometric (pH) titration and the final coprecipitate compositions were examined by chemical analysis, infra‐red spectrophotometry and thermal analysis.

The coprecipitates onto aged α‐FeOOH were simple mixtures of α‐FeOOH and Mg(OH)2. The main coprecipitates were either «molecular inclusion mixtures» of microcrystalline α‐FeOOH with excess Mg(OH)2 or similar mixtures of Mg(OH)2 with excess α‐FeOOH and some ten‐twenty percent (relative to the Mg content) of magnesium hydroxo‐ferrate(III) hydrate Mg[Fe(OH)4]2 · h H2O. The coprecipitates aged in alkaline magnesium hydroxide suspension at 20 °C and 40 °C were mixtures of Mg(OH)2, α‐FeOOH and forty to ninety percent (relative to the Mg content) of Mg[Fe(OH)4]2 · h H2O.

The related α‐FeOOHNaOH and α‐FeOOHMg(OH)2 equilibria and the different coprecipitation mechanisms are discussed.
Interatomic Interaction in Zn3(PxAs1–x)2 Solid Solutions
Authors: Vitkina Ts. Z. , Orlik L. K. , Smolyarenko E. M. , Ttrukhan V. M.
Published: January 2007

Peculiarities of the interatomic interaction in the Zn3(PxAs1–x)2 (0 ≦ x ≦ 1) solid solutions are discussed in terms of the magnetic susceptibility data. It is shown that the dependence χmol(x) has a break at x ≈︁ 0.15 which is, apparently, associated with the transition from the structures with indirect optical transitions to those with direct optical ones in the above mentioned system. In the framework of the MOLKAO model the magnetic susceptibility is divided into the Langevin diamagnetic and the Van Vleck paramagnetic components.
Simplified Treatment of Transient Doping Behaviour in CVD(I)
Authors: Arnold H.
Published: January 2007

Physiochemical reasons are discussed for the delayed response of doping concentrations within epitaxial semiconductors (Si and III‐V compounds) to changes of the input partial pressure of dopant species for CVD processes. A simplified circuit representation for doping is used that takes care of five serial process steps, the first three of which are the topic of this work (Part I).

Among the corresponding storage phenomena in which the gas phase is involved, those with adsorptional influences are to be expected as most important for transient behaviour. Storage of dopant species at the semiconductor surface is included into the circuit representation, as it has been done by Reif et al. for silicon doping. Moreover, adsorption at the reactor wall is represented approximately, assuming equilibrium with the gas phase.
Theoretical Study of Intragranular Heterogeneity of Deformation and Crystal Rotation
Authors: Wierzbanowski K. , Berveiller M.
Published: January 2007

The paper deals with the problem of the intragranular heterogeneous deformation. The grains of a deformed polycrystal are divided in general into subgrains (or deformation zones). In each subgrain a different set of slip systems and consequently a different crystal rotation may occur. We have examined theoretically both the homogeneous and the heterogeneous deformation in tension of a grain using the model of the plastic inclusion(s) in an elastic matrix. The crystal structure and orientation as well as the interactions between slip systems have been taken into account. For both situations (homogeneous and heterogeneous) we have compared resulting deformation energies, active slip systems and crystal rotations. We conclude that for some configurations of heterogeneity it is possible to minimize the total deformation energy.
The Order‐Disorder Structure of Carbamazepine Dihydrate: 5 H‐Dibenz [b, f] azepine‐5‐carboxamide Dihydrate, C15H12N2O · 2 H2O
Authors: Reck Günter , Dietz Günther
Published: January 2007

The crystal structure of the title compound has been determined by X‐ray diffraction techniques. The structure was solved by MULTAN‐82 using the space group Aba2. The atomic parameters were refined by full‐matrix least‐squares calculations in Abam to the conventionalR‐value of 0.105, but it is impossible to interpret the results with normal space group symmetry as the title compound is an order‐disorder (OD) structure consisting of two kind of layers. The OD‐groupoid family is

Ab21A1

[1/4·0].
Coincidence‐Site Lattices in the Rhombohedral System
Authors: Doni E. G. , Fanides Ch. , Bleris G. L.
Published: January 2007

Coincidence orientations in the rhombohedral system are examined by means of the CSL model. The rotation matrix R producing a CSL, the generating function ∑ and the equivalent descriptions of the same CSL in direct and reciprocal space are analytically computed. As an application, Tables of CSLs for the approximation of typical rhombohedral materials are presented.
4,2 K‐Photoluminescence Study of the Annealing Process in Neutron‐irradiated Silicon
Authors: Sickert J. , Herzog R. , Flade T.
Published: January 2007

Described are experimental results of impurity characterisation and defect kinetic studies aimed at investigating annealing processes in neutron‐irradiated silicon. In addition to Hall effect and resistivity measurements, low‐temperature luminescence spectroscopy has been made use of for the physical characterisation, making it possible to determine shallow impurities and observe their kinetic during annealing, especially with respect to phosphorus activation, along with the changes in the electrical properties.
On the Possibility of the Determination of the Rotation Rate Field from Texture Data
Authors: Wierzbanowski K.
Published: January 2007

Three methods are proposed in order to determine the rotation rate field from experimental texture data. These methods need five, three and two “neighbouring” texture functions, respectively. The advantages and limitations of each method are mentioned.
Deformation‐induced After‐Glow in [(C2H5)4N]2MnBr4 Crystals
Authors: Chandra B. P. , Deshmukh N. G. , Sahu R. B. , Verma A. K.
Published: January 2007

The mechanoluminescence appears in [(C2H5)4N]2MnBr4 crystals even after their mechanical deformation. During the excitation of mechanoluminescence by the impact of a piston on to the crystals, the peak corresponding to the mechanoluminescence intensity versus time curve and the total intensity of mechanoluminescence increase with the impact velocity and decrease with the temperature of the crystals. It seems that the electric field produced during the inpact of the piston on to the crystal may perturb the ground and excited states of the molecules comprising the crystals. Thus the mechanoluminescence may follow the rate of compression during the deformation of the crystal and it may decay with the decay rate of phosphorescence after the compression. The mechanoluminescence and high pressure photoluminescence spectra are also reported.
The distribution coefficient of zinc during the crystallization of GaP from nonstoichiometric gallium melts
Authors: Koi H. , Buhrig E. , Hein K.
Published: January 2007

Experiments were carried out to calculate by defining equations the distribution coefficient of zinc during the crystallization of GaP from the nonstoichiometric gallium melt. The TGS technique was applied to grow the crystals. Zinc detection was performed by the use of the radionuclide Zn65 as a tracer. The distribution coefficient being of the order of 0.1 is dependent upon temperature and concentration. These relations are demonstrated by plots and discussed with special respect to the literature data.
Growth of NaA zeolites in the presence of triethanolamine (TEA). The influence of water, TEA and Al contents
Authors: Schmitz W. , Kornatowski J. , Finger G.
Published: January 2007

In order to obtain larger NaA zeolite crystals, the influence of starting materials and preparation conditions on the crystal growth has been studied. It is shown that the growth of NaA is most sensitive to changes in the gel composition. The crystal sizes are limited by subsequent nucleation occurring during the crystallization process. At the optimum gel composition, it is possible to grow crystals up to 75 μm in 100–400 ml reactants.
Liquid phase epitaxy of SiC in the system TbSiSiC by temperature gradient zone melting (III). Epitaxial layer properties
Authors: Peev N. S. , Tairov Yu. M. , Smirnova N. A. , Kalnin A. A.
Published: January 2007

In the present work the electrophysical and structural properties of the SiC epitaxial layers grown by the temperature gradient zone melting method in vacuum conditions is considered. Some correlations between the epitaxial layer properties and the process conditions are observed. It is shown that the performence of the growth process in vacuum leads to a significant improvement of the layer quality, if one observes some requirements – how to decrease significantly the number of the second phase inclusions and how to improve the structural perfection of the layers.
Growth kinetics, structure and surface morphology of AlN/α‐Al2O3 epitaxial layers
Authors: Bugge F. , Efimov A. N. , Pichugin I. G. , Tsaregorodtsev A. M. , Chernov M. A.
Published: January 2007

The gas‐phase epitaxy of AlN on saphire substrates in the system AlHClNH3–Ar was investigated. The uniformity and structural perfection of the layers were shown to be determined by gas dynamics in the growth zone. The growth rate of AlN‐layer is proportional to AlCl concentration in the growth zone and does not depend on NH3 partial pressure. This is in accordance with the law of diffusional stoichiometry.

The morphology of AlN‐layers was shown to be dependent on the growth rate and the substrate orientation. Smooth mirror‐like layers were prepared on the sapphire planes (0001) and (1120) at low growth rates.

X‐ray microanalysis showed the oxygen impurity content at the level 1 — 5 · 1021 cm−3. Other impurities were not available.
Electrical conductivity and crystal structure of pure and SrCO3‐doped Na2CO3
Authors: Guth U. , Barwisch F. , Wulff H. , Schmidt P. , Möbius H.‐H.
Published: January 2007

The electrical conductivity of pure and SrCO3‐doped sodium carbonate has been measured in the temperature range 310–800 °C in air using a dc technique. Its concentration dependency is similar to that of the K2CO3–SrCO3 system described recently (GUTH et al. 1986). The maximum conductivity could be observed at ≈ 20 mol.% SrCO3. At temperatures > 440 °C, the conductivity of Na2CO3–SrCO3 mixtures containing up to 80 mol.% SrCO3 is larger than that of pure Na2CO3. X‐ray investigations of slowly cooled samples show the mixtures to be heterogeneous. X‐ray diffraction patterns of quenched mixtures containing 10 mol.% SrCO3 show reflexes of a high temperature compound. SrCO3, however, could not be detected. The lattice constants of this hexagonal compound Na2Sr4(CO3)5 which is isotyp with Na2Ca2Sr2(CO3)5 described by CHEN and CHAO are a0 = (1066.1 ± 0.4) pm and c0 = (653.2 ± 0.2) pm.
High‐temperature annealing stages in irradiated imperfect crystals
Authors: Larikov L. N. , Borimskaya S. T.
Published: January 2007

The effect of neutron irradiation on the structure of crystals with different dislocation densities and types of crystal lattice and on subsequent high‐temperature annealing is studied. The extent of this effect is determined by the substructure of irradiated material. The processes responsible for stage V and VI annealing of radiation‐induced defects are investigated by quantitative X‐ray diffraction topography and two‐crystal spectrometer technique. A retarding effect of neutron irradiation on all the stages of recrystallization is established enabling the temperature range of application of hardened metal and alloys to be shifted to higher temperatures.
Kinetics of crystallization of potassium chloride from aqueous solutions at 30 °C
Authors: König Ax. , Emons H.‐H.
Published: January 2007

The aim of this work is to use a diffusion layer model for the determination of individual rate constants of reaction and diffusion step of KCl at 30 °C. Crystal growth rate was measured by travelling microscope technique. From the measured values of the mean linear growth rate the resulting individual rate constants and the effectiveness factors (GARSIDE) are evaluated as a function of the driving force and of the flow velocity of solution. The significance of diffusional and surface reaction resistances against mass transfer is discussed in relation to the experimental conditions used.
Tracing of dislocations in ammonium hydrogen tartrate single crystals
Authors: Desai C. C. , Hanchinal A. N.
Published: January 2007

Sparingly soluble ammonium hydrogen tartrate (AHT) crystals are grown by the gel method, derived from the diffusion of ammonium chloride into the set gel containing tartaric acid. Crystals up to 23 × 5 × 3 mm3 in size are grown at room temperature. AHT crystals are cleaved along (010) planes and the cleavage surfaces are studied by using multiple beam interferometry. The interferograms have revealed that the cleavages are quite flat. An attempt is made to trace the trajectory of dislocations of isolated as well as matched pairs of (010) cleavages of AHT when etched in a mixture of formic acid and methyl alcohol (2:1) and 1.0 M SrCl2 solutions. Optical and transmission electron micrographs of dislocations show oblique, parallel and continuous line characteristics. Rows of equally spaced dislocation pits are observed and the implications of this are discussed.
Probability analysis of the azimuthal distribution of glide traces on the surface of plastically deformed polycrystalline metals
Authors: Preuss Heinz H. W.
Published: January 2007

With the simple assumption of an isotropic distribution of grain‐orientation (absence of texture) and independent plastic deformation of the grains, when by increasing load some constant limit of the resolved shear stress is reached for any slip system within the grain, one can find the azimutal distribution of glide traces on the free surface of the material by crystallgeometrical probability analysis. The azimutal distribution is independent on crystal symmetry and is characterised by a gap symmetrically arranged around the stress direction and by a flat minimum perpendicular to the stress direction. The height of the minimum does not depend upon the level of stress but is nearly a linear function of the real local plastic deformation as a consequence of developing texture.
The crystal structure of nematogenic 2‐bromo‐1,4‐phenylenediyl bis(trans‐4‐n‐propylcyclohexanoate) — a special kind of disorder
Authors: Hartung H. , Winter G.
Published: January 2007

The title compound with the formula C3H7–C6H10–COO–C6H3BrOOCC6H10C3H7 (BPBPC) crystallizes in a triclinic unit cell with dimensions a = 5.822(2), b = 8.732(3), c = 13.016(5) Å, α = 94.42(3)°, β = 93.47(3)°, γ = 104.85(2)° containing one molecule. The structure has been solved by heavy atom method and refined to R = 0.083.

The BPBPC molecules adopt an optimum stretched form and exhibit pseudo‐centrosymmetry in consequence of a special kind of disorder within the crystal lattice.
Microhardness of tetrahedrally bonded elemental and binary semiconductors
Authors: Neumann H.
Published: January 2007

An analysis of experimental microhardness data shows that the microhardness at room temperature of the diamond, zincblende and wurtzite structure compounds follows the simple relation H = hoa−xTm(1 –gofi) where a is the lattice parameter Tm the melting temperature, fi the spectroscopically defined bond ionicity and ho, x, and go are constants having the same values for all compounds. The close relation between microhardness and bulk modulus is discussed.
The influence of natural convection on the mass transfer kinetics in LPE growth
Authors: Nghi Nguyen Thanh , Khang Dao Duc , Tuan Duong Anh , Nghia Nguyen Xuan , Hai Nguyen Thi Qui
Published: January 2007

The simplified scheme has been suggested for quantitative estimation of the effect of natural convection on the LPE layers thickness while growing from a finite solution with parallel horizontal and vertical substrates. The convective‐diffusive mass transfer model is being developed on the base of boundary layer approximation. In the case of horizontal growth the layer thickness is determined by effective solution thickness which is distinguished for an upper and lower substrate and depends on convection intensity. For the vertical growth system the expression describing the variation of layer thickness along the substrate has been obtained and the vertical temperature gradient necessary for eliminating a wedge shaped growth in this case is calculated.

The experimental investigations of LPE growth of GaP layers from finite solution with horizontal and vertical substrates are carried out. The thickness and shape of LPE layers obtained in both cases coincide well with results of calculation.
Continuous magnesium hydroxide precipitation
Authors: Dobrescu V. , Păraşcu E. , Pincovschi E.
Published: January 2007

The main kinetic parameters of the precipitation process of magnesium hydroxide from magnesium nitrate have been determined. By using gaseous ammonia as precipitation agent in a 20% stoichiometric excess and in a reactor residence period of 30–60 min we determined the total kinetic order of the process, which is 2.67. For a 50 min residence time, we determined the filtration and washing parameters for the magnesium hydroxide obtained from the beginning of the precipitation process till a stationary state was reached.
The precipitation of iron (II) and nickel oxalates with alkaline‐earth metal oxalates: Induction periods, nucleation rates and mechanisms
Authors: Packter A. , Chauhan P. , Omomo A.
Published: January 2007

The coprecipitations of magnesium (and barium) iron(II) and nickel oxalate dihydrates were studied from excess magnesium and barium oxalate solutions. Nucleation rates were estimated from the induction periods for the coprecipitations. The nucleation rates in excess magnesium oxalate solutions first decreased with increasing excess oxalate anion concentration to minimum values and then increased with increasing magnesium cation concentration. At low to intermediate Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were FeOx (and NiOx); at intermediate Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were probably MgOxFeOx (and MgOxNiOx) mixtures and/or solid solutions of compositions MgαFe1αOx (and MgαNi1αOx); at high Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were MgOx.

The nucleation rates in excess barium oxalate solutions were similar to those for the precipitation of barium oxalate from supersaturated equivalent solutions. The main nuclei in most systems were BaOx.
An analysis of the applicability of the Scheil equation in the determination of segregation in monocrystals of the manganese‐zinc ferrites Mn1xZnxFe2O4
Authors: Wołczyński W. , Guzik E.
Published: January 2007

Theoretical assumptions concerning the segregation phenomenon of alloying components during formation of monocrystals of the manganese‐zinc ferrite Mn1xZnxFe2O4 have been presented. Taking into account the case of the unidirectional solidification of the above ferrite by means of the Bridgman furnace, which is working in:

Closed system.

Open system, with adding of the pure component (melting at an elevated temperature).

Open system, with adding of ferrite of a nominal composition.

The method for calculation of alloying components segregation has been analysed. A possibility of modelling the segregation by means of the choice of the size of the melting zone has been considered for a given monocrystal.
The crystal and molecular structure of 2,6,11‐tribromo‐14‐oxabicyclo[8.3.1]tetradec‐6(E)‐ene – A transannular O‐heterocyclization product of a thirteen membered triene
Authors: Sieler J. , Richter R. , Haufe G. , Faure R.
Published: January 2007

The crystal structure of the title compound has been determined from single‐crystal X‐ray diffractometer data collected with a CAD‐4 diffractometer. C13H19OBr3 crystallizes in space group Pbca with a = 24.005(6) Å, b = 12.038(4) Å, c = 10.397(2) Å and Z = 8. Leastsquares refinement gave an R value of R = 0.057 for 1072 observed reflections I > 3σ(I). The investigated product is a bicyclic tetrahydropyran compound with a vinylic bromine atom.
Molecular geometry and tautomerism of 2‐carboxymethylamido‐3(4H)‐quinoxalone
Authors: Pfeiffer D. , Scharfenberg P. , Reck G.
Published: January 2007

2‐Carboxymethylamido‐3(4H)‐quinoxalone cyrstallizes in the triclinic space group P1 with four molecules per unit cell (a = 8.797, b = 11.240, c = 11.099 Å, α = 85.62, β = 67.75, γ = 67.35°). The structure was solved by direct methods and refined by fullmatrix least squares calculations to the final R‐value of 0.042.

The tautomeric equilibrium of the compound is discussed in connection with the molecular conformation and the ability to form intramolecular hydrogen bonds. Evidence is given that the oxo form of 2‐hydroxyquinoxalines largely dominates and that 5‐membered intramolecular chelates involving H‐bonds of the type (N, O)H…(N, O) are so weak that they usually do not govern conformational equilibria.
The properties of application of the electron probe X‐ray microanalysis in the high‐temperature range particularly for the study of diffusion processes and phase formations
Authors: Däbritz S. , Ullrich H.‐J. , Kleinstück K.
Published: January 2007

In this study the efficiency of a manufactored heating stage for the electron probe microanalyzer is presented and a methodology (High‐Temperature Electron Probe X‐Ray Micro Analysis, HT‐EPXMA seldom used till now for the determination of diffusion coefficients and activation energies, for the discovery, observation and characterization of phases in the heating‐up process as well as for the investigation of crystallographic parameters of phase transformations is obtained.
Electrooptic behaviour of a nematic MBBA layer with a thick interfacial surfactant layer
Authors: Hinov H. P.
Published: January 2007

The electro‐optic behaviour of MBBA nematic layers with various surfactants added of anionic, cationic, zwitterionic and non‐ionic character and a considerable amount (2wt% to 8 wt%) was studied. The formation of surface‐induced flexoelectric domains in all cases clearly showed that the anchoring of the liquid crystal layers has been weak. Such a weak anchoring can be explained with the formation of a perioidc (in the most simple case sinusoidal) MBBA‐surfactant interface boundary with a mutual penetration of the liquid crystal and surfactant molecules with some gradient.
On the position of the upper limit temperature of homogeneous nucleation of precipitates in low concentrated AlZn alloys
Authors: Wendrock G. , Löffler H. , Raphelt I. , Truong Chu Thien
Published: January 2007

The upper limit temperature Thn of the onset of homogeneous nucleation of Guinier‐Preston (GP) zones was determined for three AlZn alloys with xZn = 4.5, 6.0 and 8.0 at.% by SAXS investigations (cooling from the range of homogeneity to various temperatures Ta and ageing at Ta). The results are Thn = (95 ± 3) °C for xZn = 4.5 at.%, (118 ± 3) °C (6.0 at.%) and (154 ± 3) °C (8.0 at.%), respectively. The obtained results fit well the data known for the alloys with higher contents of Zn.

It is stressed that one has to distinguish between Thn, determined by isothermal measurements after a direct quench or cooling to the respective Ta, and the upper limit temperature Trhn of the onset of the rapid homogeneous nucleation of GP zones (continuous cooling).
Deformation stages in a stabilized loading cycle of fatigued FCC metals(II). Discussion and conclusions
Authors: Holste C. , Kleinert W. , Fischer W.
Published: January 2007

Considering the experimental results presented in Part I of this work and taking into account the nature of the deformation mechanisms during cycling, four deformation stages are assumed to exist in a stabilized loading cycle. The mechanical behaviour in the stages is discussed on different structure levels. In particular, it is shown that the heterogeneous plastic deformation caused by different local yield stresses in the dislocation‐dense and dislocation‐poor regions of the material seems to be limited to a relatively small interval of plastic strain εp (10−4 ≦ εp ≦ 10−3).
Computer simulation of the pyramidal and prismatic growth of KDP‐type crystals
Authors: Bernhardt Hj.
Published: January 2007

The growth of KDP crystals dependent on the applied physical parameters as seed sizes pH‐value of the solution, rate of the temperature decrease and initial supersaturation has been investigated. The prismatic and pyramidal growth components have been investigated separately. A pragmatic model which is hold as simple as possible simulates numerically different shapes of the growth habit, which are caused to the variation of aforementioned parameters. The results are plotted quasigraphically. The observed shapes of the simulated habit enable us to understand some growth striations in real crystals. The time dependent behaviour of the growth velocity may be simulated, additionally.
Measurement of optical biaxiality and tilt angle in A smectic c liquid crystal
Authors: Schmiedel H. , Frieser A.
Published: January 2007

We present a new method of measuring the tilt angle and the optical biaxiality in liquid crystals (LCs). The method uses a fitting procedure of the optical path difference in specially prepared LC cells. Measurements are performed in the SC phase of 4‐n‐hexyloxyphenyl‐4n‐decyloxybenzoate (HOPDOB) by means of microscopic observations in a rotary heating stage.
Measurement of particle size and internal strain in doped tungsten powder by X‐ray methods
Authors: Salewski W.
Published: January 2007

In the powder metallurgical process of tungsten wire fabrication for incandescent lamps the stepwise reduction of tungsten oxides (WO3 or W20O58) plays an important role in respect to the efficiency of doping elements (especially potassium) for the formation of the non sag structure of tungsten wires. The influence of temperature and time in the reduction steps has been investigated by means of the X‐ray method for determination of particle size and internal strain described by KOCHENDOERFER. It has been founded a close relationship between the internal structure of metal powder (especially internal strain) and the potassium content as well as the sintering behaviour of these powders. – The KOCHENDOERFER method is a usefull tool for the improvement of reduction parameters in regard to the sintering behaviour.
Characterization of chemical perfection of YAG:Nd crystals with absorption spectroscopic methods
Authors: Bernhardt Hj. , Rauch R. , Toepfer K. , Wehrhan G.
Published: January 2007

The absorption constants of Neodymium in YAG are determined at the absorption lines 434.4 nm; 588.6 nm; 868 nm and compared with literature data. The influence of measuring parameters is discussed. The calibration of the concentration is made absorptionspectrophotometrically by comparison of chemically decomposed solutions of YAG crystals with solutions of mixtures Y2O3/Al2O3/Nd2O3.

The measurement of the near‐edge absorption is shown to be a practical method for characterization of stoichiometric composition of Nd: YAG crystals.
Sensivity of the thermal gradient flotation method
Authors: Andreev G. A. , Hartmanová M.
Published: January 2007

The theoretical sensitivity of the flotation method of density determination has been estimated. The natural pressure gradient is found to be a limiting factor and the maximum sensitivity is 3 × 10−9. In practice, the accuracy of the flotation measurements is controlled by the sample error. The main sources of sample errors have been analysed.
Theoretical investigation of phantom controlled crystal growth: Models with surface tension
Authors: Mecseki A. , Mezo B. , Voszka R. , Galántai A. , Szabó B.
Published: January 2007

Three models taking into account the capillary interaction are given for the computation of the shape of the phantom needed to grow crystals of a given profile.
Phase transition studies in the liquid crystal p‐cyanophenyl trans‐4‐propylcyclohexane carboxylate
Authors: Venkatacharyulu P. , Gupta A. V. N. , Rao L. V.
Published: January 2007

The specific volume and ultrasonic velocity measurements (at four different fixed frequencies) are carried out in the liquid crystal p‐cyanophenyl trans‐4‐propylcyclohexane carboxylate. From these studies various physical parameters like adiabatic compressibility, molar sound velocity, molar compressibility, Van der Waals' constant and intermolecular free lengths are derived. The variation of the order parameter with temperature at the four fixed frequencies is also studied. The results are discussed.
The current understanding of epitaxial CVD silicon doping in the light of modelling and theory development (III). The law of epitaxial layer doping and its limitation
Authors: Kühne H.
Published: January 2007

Various doping mechanisms discussed in recent literature are applied to the theoretical concept derived in the previously published Part II of the paper, whereby a variety of hypothetical laws of dopant incorporation is revealed. Those laws cannot be distinguished from each other by doping experiments, but are testable, at least in principle. When substituting three doping‐process‐relevant empirical constants, all of them might be changed into that single empirical, but theory‐aided model equation, which enables apitaxial layer doping to be described as a result of intended variations of the main process parameters: partial pressure of the dopant source, layer growth rate, total pressure, and deposition temperature.
On the origin of the (1216)‐orientation in epitaxial AIN layers on R‐plane sapphire
Authors: Georgi Ch.
Published: January 2007

Epitaxial AIN grown by MOCVD on (0112)Al2O3 substrates usually is (1210)‐oriented. Here for the first time (1216)AIN was found in MOCVD layers. This AIN orientation is known from other growth techniques, its origin is generally not understood. An explanation is given based on twinning in the early growth stages which is also applicable to the growth of (1216)ZnO on (0112)Al2O3.
Structure determination of polytypes (I)
Authors: Sedlacek P. , Kuban R.‐J. , Backhaus K.‐O.
Published: January 2007

Crystal structure determination of polytypes with diffraction methods can be divided into two steps. The first step is the structure determination of the building unit of the polytypic substance (in most cases layers). The second step is the determination of the stacking sequence of the corresponding building units. The stacking can be ordered as well as disordered. Various methods for solving these problems are described. The aim of this paper is to treate these methods from a uniform point of view.
Surface structure of obliquely deposited layers and liquid crystal alignment
Authors: Hauck G.
Published: January 2007

The dependence of the orientational action of obliquely deposited SiOx layers on the deposition angle and the residual gas pressure has been investigated. The variation of the pressure gave rise to a modification of the general dependence of the pretilt angle of liquid crystals on the deposition angle. A model has been developed which explains the action of all deposition parameters on the orientational behaviour of liquid crystals. In a first step, some tendencies of the layer formation are stated. Thereby, in a second step, it is possible to explain the change in the orientation at variations of deposition parameters using the knowledge of these tendencies and experimentally stated informations on the relative change of layer parameters.
The influence of crucible moving on growth rate and perfection of SSD‐GaP crystals
Authors: Weinert B. , Kirsten P. , Siegel W.
Published: January 2007

The influence of the crucible moving (lowering, rotation) during the SSD growth of GaP on the growth rate and the crystal quality is investigated. The crucible lowering leads to an improvement especially of the crystal quality characterized by the size of the single crystalline regions and by the homogeneity of the impurity incorporation. On the other hand, the crucible rotation yields no noticeable improvements (in the case of constant frequency) or a strong increase of the growth rate connected with a deterioration of the crystal quality (accelerated rotation).
The nematic reentrant phase in binary mixtures composed of a 4‐(trans‐4‐alkylcyclohexyl)‐1‐(2‐cyanoethenyl)‐benzene and 60CB
Authors: Dąbrowski R. , Jadźyn J. , Przedmojski J. , Baran J.
Published: January 2007

It is shown that the smectic A phase in the 4‐(trans‐4‐n‐alkylcyclohexyl)‐1‐(2‐cyanoethenyl)‐benzene EPCH homologous series has a partially dimolecular structure of Ad type. The EPCH compounds show a virtual SAd → Nre transition revealed in mixtures of 60CB with members of the homologous series with five or more carbon atoms in the alkyl chain. The temperature dependences of electric conductivity and electric permittivity of the 8EPCH‐60CB mixture have been tested in the three successive phases, Nre, SAd and N.
The current understanding of epitaxial CVD silicon layer doping in the light of modelling and theory development (IV). The problem of more‐than‐one kind of dopant species
Authors: Kühne H.
Published: January 2007

In Part IV of the present treatise epitaxial silicon layer doping governed by the ratelimiting action of more than one kind of dopant species in the gas is investigated on the theoretical basis which has been derived in the previously published parts. It is shown that both the general reaction scheme of forward and backward reaction steps and the general differential equation statement of counterbalancing the fluxes of those reaction steps and the dopant incorporation flux are suitable for solving the problem under consideration. Only two of the four incorporation‐limiting reaction mechanisms, being discussed in the more recent literature, fulfill the requirements needed to agree with experimental findings on the one hand and with the limiting case situation of equilibrium incorporation on the other. Arsenic has been selected as the demonstrating dopant element.
Characterization of epitaxial group II fluoride films on (100)‐oriented GaAs substrates by ion backscattering and channeling
Authors: Flagmeyer R. , Schumann B.
Published: January 2007

Lattice matched (Ca, Sr)F2 and related fluoride films grown on (100)GaAs substrates were investigated by Rutherford backscattering/Channeling. This technique allows the characterization of the 30–250 nm thick heteroepitaxial layers with respect to chemical composition, film thickness, interface roughness and crystalline perfection. The first flash evaporated GaAs/fluoride/GaAs structure are briefly reported.
Are in‐growth surface reactions during MBE controlled by a “Quasi‐Gas transition layer”?
Authors: Wolf B. , Zehe A.
Published: January 2007

Recently a new growth model for Molecular Beam Epitaxy (MBE) was presented in literature (HERMAN, ANDERSSON), that assumes a gas‐like transition layer between the ordered crystal and the vacuum. Known experimental results fit the picture of a disordered layer on top of a growing crystal which reacts much quicker with residual gas constituents than the static surface does. Following this idea, consequences of the “Near Surface Quasi‐Gas” model (NSQG model) with respect to increased chemical reactivity during MBE growth are discussed in the present paper.
Phase structure of boride layers on iron substrates with electroplated cobalt layers
Authors: Bochmann G. , Klaus E. , Fritsche G. , Wagner W.
Published: January 2007

Specimens made of Armco iron were electroplated with cobalt and then boronized with 2.2 vol% BCl3 in H2 at 1223 K. The boride layers obtained show the sequence of crystallographic phases which is (Co, Fe)B, FeB, Fe2B, substrate material.
Irradiation plus annealing‐induced 1.20 eV emission band in p‐type GaAs
Authors: Glinchuk K. D. , Guroshev V. I. , Prokhorovich A. V.
Published: January 2007

The effect of 2.2 MeV electron irradiation and subsequent annealings on the luminescence of tellurium‐compensated p‐type GaAs crystals is studied and analyzed. A comparatively strong emission band peaked at hvm near 1.20 eV (induced by radiative electron recombination in TeAsVGa pairs) appears in irradiated annealed (at T ≧ 250 °C) compensated p‐type GaAs. The data obtained testify about the following: a) electron irradiation of GaAs creates stable (at T ≦ 200 °C) defects not only in the arsenic sublattice of GaAs, but in its gallium sublattice too; b) radiation plus annealing (r.p.a.)‐induced TeAsVGa pairs are characterized by a rather high (compared to that for grown‐in TeAs VGa pairs) probability of electron radiative transitions in them. The electrical characterization of the r.p. a.‐induced 1.20 eV radiative centres (TeAsVGa pairs) is given.