bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation for an Oriented Eutectic Interface of Constant Curvature
Authors: Wołczyński Waldemar
Published: January 2007

Calculation of interface shape for oriented eutectic growth has been proposed for regular structure formation. The constant interface curvature has been applied in the analysis. The obtained function contains some physical factors which affects the formation of concave‐convex interface. The proposed approach has been related to the theory of completely coupled growth.
The Morphology of Some Hydrothermally Synthesized Li‐Minerals: A‐Zeolite, α‐Eucryptite, β‐Spodumene and β‐Eucryptite
Authors: Ghobarkar Habib
Published: January 2007

The hydrothermal treatment of glass with the composition 2 LiF, Al2O3, 3 SiO2 at 1 kbar in the range of 150 °C to 850 °C gave rise to the formation of A‐zeolite with orthorhombic unit cell with å = 10.31 Å/b̊ = 8.18 Å/c̊ = 5.0 Å (space group Pna21), α‐eucryptite, trigonal, å = 13.4 Å/bº = 13.4/Å/cº = 9.0 Å (space group R 3), β‐spodumene, pseudocubic/tetragonal, å = 7.53 Å/b̊ = 7.53 Å/c̊ = 9.15 Å (space group P43212), β‐eucryptite, monoclinic, å = 7.75 Å/b̊ = 5.2 Å/c̊ = 11.16 Å (space group P6222).

The morphology and development of the mineral phases depend on the temperature of formation.
Parabolic Approximation to the Shape of Oriented Eutectic Interface
Authors: Wolczyński Waldemar
Published: January 2007

The calculation of interface shape for oriented eutectic growth has been presented for regular structure formation. The parblic approximation to the interface shape has been assume in the proposed model. The differences between the modes of both phases growth have been distinguished. The proposed calculation of the interface shape provides a justification for the existence of lead distance. The obtained equations contain the physical factors which affect the formation of concave‐convex interface. The periodic character of interface shape shape has been taken into account. The proposed model has been related to the theory of completely coupled growth.
Synthesis and Characterisation of Scandium (III)‐, Yttrium (III)‐, and Lanthanum (III) Violurate Complexes
Authors: Gad A. A. M. , Farag I. S. Ahmed , Awadallah R. M.
Published: January 2007

Sc3+‐, Y3+ ‐and La3+ violurate complexes were prepared. The isolated complexes are freely soluble in water, dilute mineral acids, MeOH, Me2CO, DMF, DMS, partially soluble in AcOH and insoluble in EtOH, CHCl3 and CCl4. Molecular compositions of the complexes were formulated on the basis of elemental analysis, molar conductivity and infrared spectra. The IR spectra of violuric acid and its metal complexes reveal that bonding takes place through coordination bond between the central metal ion and the oxygen atom of the oxygen atom of the oximino (CN = O) group and convalenet bond between the central metal ion and oxygen atom of the phenolic (ketonic, COH) group in the case of 1:2 and 1:3 complexes, and through coordination bond between the central metal ion and COH and NH groups in the case of 2:3 complexes. All the isomorphous complexes detected by the X‐ray powder patterns [the (2:3) Sc3+‐VA and (2:3) Y3+‐VA complexes, (1:2) Sc3+‐VA, (1:2) Y3+‐VA and (1:2) La3+‐VA complexes, and the (1:3) Y3+‐VA and (1:3) La3+‐VA complexes] have similar X‐ray, eletronic and IR spetrograms and chemical formulae. The electronic spectra in DMF and in nujol mulls characterise the octahedral stereochemistry for the investigated complexes.
Correlation and Multivariate Dependencies in the X‐ray Characterization of Cr, Al‐ZSM‐5 Type Zeolites
Authors: Marcusson P. , Kosslick H. , Maess B. , Szulzewski K.
Published: January 2007

For an earlier described zeolite synthesis (Kosslick et al.) X‐ray diffraction measurements were done. The relations between the intensities of X‐ray peaks and background to other characterizing parameters were analyzed using statistical methods. it was found that the X‐ray data are a “fingerprint” of the synthesized zeolites, because the crystallinity and structure influences many other properties of the samples. Therefore, the used X‐ray data allow a comprehensive characterization of the synthesis products.
Elastic and Thermoelastic Properties of Triclinic K2Cr2O7
Authors: Haussühl S.
Published: January 2007

Large single crystals of optical quality of triclinic K2Cr2O7 have been grown from aqueous solutions. Their morphological and growth properties are not compatible with point symmetry 1. Complete sets of the elastic constants and their temperature derivatives were determined from ultrasonic resonances of plane‐parallel plates. The elastic behaviour and also the thermal expansion are highly anisotropic. Owing to very strong photoelastic effects these crystals are suited for certain acousto‐optic deflection devices.
Crystal Growth in Gels at Elevated Pressures: The Upper Limit of Temperature for Metastable Formation of Aragonite
Authors: Franke Walter A. , Mehran Nosrat‐Aga
Published: January 2007

Both rapid precipitation and diffusion controlled gel growth were applied to crystallize calcium carbonate at temperatures in the range of 100 °C to 270 °C. The amount of aragonite was determined by means of X‐ray diffraction data. The morphology of the aragonite crystals are described. Metastable formation of aragonite was observed only at temperatures below 270 °C.
Crystal Growth in Gel: Nuclei and Precipitation Distribution in Gel
Authors: Brevnova O. A. , Goshka L. L. , Ruzov V. P.
Published: January 2007

The investigation of the gel structure and properties influence upon the crystallization processes have been carried out and are reported in this paper. The gel acidity and nucleation centers distribution are chosen as the parameters describing this process. The analytical approximations for the nucleation and precipitation density along the gel column are proposed. It has been shown that in the view of the parameters chosen it is impossible separately to determine the gel structure and proton concentration effects on crystallization processes.
Growth and Properties of BeO · 3 Al2O3 (BHA) Single Crystals
Authors: Peicong Pan , Xiaoshan Ma , Zhiwei Hu
Published: January 2007

Large single crystal of BeO · 3 Al2O3 (beryllium hexa‐aluminate or BHA) doped with chromium up to 20 mm in maximum diameter and 60 mm long were grown by Czochralski method. Thechnological conditions of crystal growth have been introduced and key factor leading to a successful growth is a adequate composition of starting charge mixture other than stoichiometry. The crystal structure, absorption spectra and fluorescence spectra of BHA: Cr3+ have been measured. Vibronic side band of the fluorescence spectra is from 700 nm to 900 nm.
Synthesis of Fine‐grained NaA‐type Zeolites from Superalkaline Solutions
Authors: Hadan Marianne , Fischer Falk
Published: January 2007

The synthesis of NaA‐type zeolite from superalkaline reaction mixtures by influence on the formation‐ and transformation rate of the polymorphous phases according to the Ostwald step rule is discussed. The appearence time of NaA as a single crystallization product is described in dependence on the reaction conditions. The kinetics of the zeolite crystallization and the property alterations of the reaction products in dependence on the time are investigated in the pilot scale.
Modelling of Thermal Conditions in GaAs Crystal Growth by the Gradient Freezing Technique (I) Fundamentals
Authors: Hein K. , Buhrig E. , Göhler H.
Published: January 2007

In the gradient freezing process crystal growth is fully controlled by influencing the thermal conditions. The method described in this publication combines measurements with Si phantoms with their modelling by calculation and the extrapolation of the material properties to GaAs. Results show that the gradients in time and space and the crystallization rate are interrelated and influenced by technological and design factors. For process control in the gradient freezing process, accurate knowledge of the differences between the time‐temperature programs given by the automatic control system and the actual thermal regime in the crystal is required.
Crystal Structure of Microclusters of Silver
Authors: George K. C. , Abdulkhadar M.
Published: January 2007

Finding the crystallographic structure of clusters is a crucial and challenging problem. The properties like lattice concentration, unusual crystal symmetries etc. of metal clusters have been studied recently. We report here a 15% lattice concentration for silver clusters produced by Bredig's method.
Comparative Consideration of Photoreflectance and Electroreflectance Spectra of Semiconductors (I) Theoretical Relations
Authors: Neumann H.
Published: January 2007

Theoretical relations for photoreflectance and electroreflectance spectra of semiconductors are derived without any restrictions regarding the modulation field. For very low modulation fields it is found that the responses of both types of spectra are directly proportional to each other with the electroreflectance signal just twice as large as the photoreflectance signal. At moderate and high modulation fields the spectra are no longer proportional to each other.
The Thermal Response Function of Traditional Knudsen‐Cells in MBE
Authors: Wolf B.
Published: January 2007

Precise thermal control of Knudsen‐type evaporation cells in MBE requires basic knowledge on the thermal behaviour of the cell on any alteration of the heating power. This paper deals with the cell's response in temperature, when the cell is subject to a jumplike change in heating power. Particular care is devoted to deviations from pure exponential behaviour, if the temperature transition function between two equilibrium states is concerned. It is shown, that the jump response function for a finite increase in heating power is equivalent to that of an infinite small one, whereby an effective temperature — amounting to 70% of the temperature jump height — has to be introduced.
On the Inhomogeneity of Refractive Index of CaF2 Crystals for High Performance Optics
Authors: Dressler L. , Rauch R. , Reimann R.
Published: January 2007

CaF2‐crystals belong to the standard materials, used in optical precision instruments. As well as the traditional optics for microscopy new developments in the field of DUV‐lithography (projecting lenses made out of CaF2 and quartz) need a homogeneity of the refractive index in the order of 10−6, but over much larger volumes (diameter of the projecting lenses for lithography >100mm). Some interesting physical connections between the real structure of the crystals and the homogeneity of refractive index are discussed.
Silicon Doping of GaAs Single Crystals
Authors: Moravec F. , Štěpánek B. , Šestáková V.
Published: January 2007

The silicon doped GaAs single crystals were grown by means of a horizontal Bridgman method. The relation between the free carrier concentration and silicon concentration determined by chemical analysis was examinated.
Comparative Consideration of Photoreflectance and Electroreflectance Spectra of Semiconductors (II). Numerical Calculations for n‐type GaAs
Authors: Bouamama Kh. , Neumann H.
Published: January 2007

Photoreflectance and electroreflectance spectra of n‐type GaAs are calculated as a function of the doping level, the field modulation and the broadening energy. As a general result it is found that, except in the limiting case of very low modulation fields, the electroreflectance and photoreflectance signals are not proportional to each other. The influence of the various parameters on the spectra is discussed.
“Amorphous” Precursors of α‐Al2O3: An Electron Optical Study
Authors: Brand P. , Dietzmann P.
Published: January 2007

Basic aluminium chloride gels are thermally decomposed into X‐ray amorphous products. Corundum begins to crystallize in them about 400 °C on certain conditions. Electron optical examinations on powders of corundum‐forming gels and of their decomposition products show in an essential part aggregates of sheetlike components as powder particles. These have sharp electron diffraction patterns. The interpretation of diagrams proves the existence of two different structures with similar lattices, which are evidently related to those of diaspore and corundum. A defect structure is to be assumed for the corundum crystals formed.
The Thermal Conductivity of Monocrystalline Gallium Garnets Doped with Rare‐Earth Elements and Chromium in the Range 6–300 K
Authors: Sirota N. N. , Popv P. A. , Ivanov I. A.
Published: January 2007

The effect of the additions of rare‐earth elements Nd, Sm, Eu and Tb on the thermal conductivity of gadolinium‐gallium garnets and besides the influence of the joint doping with Nd and Cr on the thermal conductivity of gadolinium‐gallium and more compound gadolinium‐scandium‐gallium, gadolinium‐magnesium‐zirconium‐gallium and yttrium‐scandium‐gallium garnets have been investigated.
Crystal Growth and Structure of 4‐Aminobenzophenone (ABP)
Authors: Genbo Su , Zhengdong Li , Fen Pan , Youping He
Published: January 2007

4‐aminobenzophenone C6H5COC6H4NH2 (ABP) is a good organic Nonlinear Optical (NLO) material. The bulk crystal has been grown by cooling method from organic solution, and the crystal structure determined by X‐ray diffraction.
Modelling of Thermal Conditions in GaAs Single Crystal Growth by the Gradient Freezing Technique (II) Technology
Authors: Hein K. , Buhrig E. , Richter Th.
Published: January 2007

The fundamentals of the gradient freezing process were dealt with in the first part of this publication. The second part describes aspects of the thermal technology of the process. Temperature measurements in model crystals and temperature field calculations show how the thermal conditions are influenced by the quality of furnace design, the size and position of the charge, installations in the furnace, and the effect of the melting enthalpy. A characteristic example of the gradient freezing technique is derived from the results.
On the Kinetics of Interface Processes on Silver Halide Crystals
Authors: Winzer A.
Published: January 2007

In the present paper the activation energies of the transport of Ag+ ions in AgCl and AgBr crystals are calculated with the help of a quantum theoretical equation involving the frequency of the optical phonons of the crystal lattice, the mean coordination number for the diffusing ion, and the vibrational quantum number. Comparison of the calculated activation energies with values available from the literature, which were obtained by measurements of electrical conductivity, dielectric loss, diffusion and mass transfer processes, shows good agreement.
Ultrasonic Investigations in the Liquid Crystal p‐Cyanophenyl‐trans‐4‐Propylocyclohexane Carboxylate
Authors: Venkatacharyulu P. , Gupta A. V. Nagaraja , Rao K. R. K. , Rao J. V.
Published: January 2007

The variation of ultrasonic velocity with temperature in the liquid crystal p‐cyanophenyl‐trans‐4‐propylcyclohexane carboxylate at four different fixed frequencies is studied. From the observed temperature variation of the ultrasonic velocities, relaxation parameters like adiabatic relaxation time, velocity at infinite frequency in the isotropic as well as in the nematic liquid crystalline phases are determined. The results are discussed.
Sythesis and Characterization of Li3B5O8(OH)2 Crystals
Authors: Byrappa K. , Shekar K. V. K. , Gali S.
Published: January 2007

Li3B5O8(OH)2 crystals were obtained in the system Li2OB2O3H2O under hydrothermal conditions at fairly lower PT conditions. The crystals obtained were characterized through various techniques: XRD, wet chemical analysis and the measurement of ionic conductivity.
Evolution of Optical Transmittance in Precipitants Solutions. A Computer Simulation
Authors: Martín J. , García‐Ruiz J. M. , Alcántara R.
Published: January 2007

We present a computer simulation model of the evolution of the transmitted light intensity traversing a reservoir that contains a supersaturated solution. From the analysis of the noise associated with the main signal, it seems to be possible to differentiate whether mass precipitation occurs by homogeneous nucleation or by pure crystal growth.
Investigation of Residual Oxide Layers on GaAs Surfaces
Authors: Marinova Ts. , Krastev V. , Yakimova R.
Published: January 2007

GaAs(100) and (111) oriented samples, treated by means of different chemical procedures, are studied by X‐ray photoelectron spectroscopy (XPS). The thickness and composition of the residual oxide layers are estimated using the intensity ration of Ga 3d and As 3d core levels from the substrate and the oxide overlayers, respectively. Residual oxides containing As2 O3 and Ga2 O3 on GaAs surface are observed. The thickness of the oxide layers is found to range from 3Å to 15 Å. Optimal conditions for pre‐epitaxial surface preparation of GaAs substrates are suggested.
Holographic Studies of Diffusivities of KDP and DKDP in the Solutions
Authors: Xiling Yu , Xuefeng Yue
Published: January 2007

The solution diffusivities of KDP and DKDP are measured accurately and conveniently by holography with a reference‐fringe system being introduced into the hologram. The influences of solutions with different concentrations, concentration gradients, deuterium concentrations and at different temperatures on the diffusivities have been studied in detail for KDP‐H2O and DKDP‐D2O systems. The problems of how to measure diffusivity accurately are discussed on the basis of diffusion mechanism and experimental technique. The activation energies for the diffusion of KDP and DKDP around the saturated solution in the temperature range of 20–50 °C are about 16 · 103J/mole and 25 · 103J/mole, respectively.
Investigations on the Quasi‐binary Subsystem VNb9O25Nb2O5
Authors: Schadow H. , Oppermann H. , Grossmann O.
Published: January 2007

By X‐ray phase analysis in connection with chemical transport reactions it was proved that two boundary phases coexist in the pseudo‐binary subsystem VNb9O25Nb2O5. The maximum solubility of V2O5 in solid Nb2O5 which was spectrometrically determined in corresponding chemically transported samples of the system is 0.37% (n/n).
About the Reliability of Approximate Methods for Analysing Photoreflectance Spectra of Semiconductors
Authors: Neumann H. , Bouamama Kh.
Published: January 2007

The approximate relation for photoreflectance spectra in the limit of weak electric fields and both correct and approximate relations for photoreflectance spectra for intermediate uniform electric fields are compared with spectra calculated with the integral method accounting for the spatial dependence of the electric field within the near‐surface space charge region of the semicondcctor. From numerical calculations performed for n‐type GaAs it follows that rather accurate critical point energies and surface electric fields are obtained provided that the width of the space charge layer is comparable with or larger than the absorption length. Sufficiently reliable values for the broadening energy of the spectra and for the light‐induced modulation of the surface electric field can only be achieved if the correct relation for photoreflectance spectra for uniform electric fields is used to analyse the Franz‐Keldysh oscillations.
Thermoluminescence and Optical Absorption Studies of Z1 Centers in KCI Crystals Doped with Praseodymium
Authors: Balraj K. , Veeresham P.
Published: January 2007

Thermoluminescence (TL) of Pr‐doped KCI is studied. The influence of pre‐heat treatment and optical bleaching of the glow curves and the production of Z1 centers are discussed. The glow curves of KCI containing 1062 ppm of praseodymium (Pr) shows one shoulder at 365 K (T1) and two peaks around 408 K (T2) and 443 K (T3), respectively. Bleaching of X‐irradiated crystals shows that the peak T2 is enhanced whereas other two (T1, T3) get suppressed. Optical absorption studies of the crystals before and after F‐bleaching shows that the F‐band decreases and shifts towards longer wavelengths. The decrease is accompanied by broadening towards the longer wavelength. The T2 peak is attributed to Z1 centres. It is shown that T1 corresponds to shallow centers and T3 peak is attributed to F‐centers.
Controls on Morphology of Analcime‐Pollucite in Natural Minerals, Synthetic Phases, and Nuclear Waste Products
Authors: Teertstra D. K. , Černý P.
Published: January 2007

Crystals of the analcime‐pollucite series (NaAlSi2O6 · H2OCsAlSi2O6) exhibit tetragon‐trioctahedral {211} and hexahedral {100} morphology, with rare modification by tetrahexahedral {210} or rhombic dodecahedral {110} forms. Under weakly acidic to weakly basic conditions {100} is dominant; with increasing alkalinity (cation concentration), basicity (pH), and temperature {211} is dominant over {100}, with minor development of {210}. The morphology does not appear to be influenced by broad ranges in Si/Al (from 2.0 to 2.6 in the natural minerals) and Na‐Cs contents between analcime and pollucite, by substitutions of univalent cations Li, K, Rb, and Tl, or by small amounts of divalent cations Mg, Mn, Ni, Zn, Fe. Larger amounts of Ca, however, and possible substitutions for framework Al and Si seem to produce a more complex morphology.
Verification and Application of Modified Kick's Law to Rhombohedral Crystals: Sodium Nitrate
Authors: Joshi D. R. , Pandya J. R.
Published: January 2007

Optical study of mechanical response indicated by Knoop indentation of cleavage faces of synthetic sodium nitrate crystal based on MEYER's Law/KICK's Law (P = adn) and also on modified KICK's Law {(P — W) = bd2} expressing relations between applied load P and diagonal length d is made. The Newtonian resistance pressure W is finite and positive. The value of standard hardness (a and b), exponent n are calculated. It is found that W and b are almost contant and independent of thermal treatment and of the indenter orientation with respect to direction [100] on cleavage plane (100) of sodium nitrate crystals. Since they are independent of indenter orientations, they are not associated with crystal anisotropy.
Thermoelectric Phenomena in Gallium Monosulphide Single Crystals
Authors: Gamal G. A. , Nassary M. M. , Hussein S. A.
Published: January 2007

Measurements of thermoelectric power of GaS single crystals grown by melt growth technique, were performed in the range of 150 K to 500 K. Investigations of GaS compound have revealed that it has interesting properties. Many physical parameters were determined such as carriers mobilities, effective masses of free charge carriers, diffusion coefficient and diffusion length as well as the relaxation time. Also the thermoelectric power behaviour showed the p‐type nature of GaS crystals.
Kinetic Investigations within the Transition Region from Polyhedral to Skeletal Growth Mode (V). Growth Kinetics of the Pyramidal Face of Zinc Single Crystals under Diffusion Conditions
Authors: Iwanov D.
Published: January 2007

The growth kinetics of the pyramidal face of zinc single crystals is studied in the presence of argon. The curves size vs. time provide evidence that smaller crystals grow in a kinetic regime and after reaching a certain critical size their growth continues in a diffusion regime. The growth kinetics of faces {101} and {0001} are compared. It is established that the growth of both faces simultaneously changes from a kinetic to a diffusion growth mode. During the transition between the two regimes, however, loss of the morphological stability only of the smooth {0001} face is observed, while the {101} face with macro steps formed on the surface acquires a skeletal shape after prolonged growth. It is shown that the appearance of morphological instability depends on the surface structure of the crystal faces.
The Mechanism as SI GaAs Substrate Influences the Resistivity of the Epitaxial Layer
Authors: Somogyi K.
Published: January 2007

It is known that it is possible to grow a semi‐insulating or, at least, a high resistivity GaAs epitaxial layer without doping on an SI GaAs substrate by VPE. The SI substrate is suspected as the originator of the high resistivity intermediate layer and diffusion and/or out‐diffusion are accepted as mechanisms explaining this effect. In this work carrier concentration depth profiles were studied in various GaAs multi‐layered epitaxial structures grown on SI GaAs substrates before and after various heat treatment procedures in order to study the diffusion and outdiffusion processes. It is concluded that the role of the diffusion is negligible and the out‐diffusion process is insignificant, and the main, i.e. the determining effect in the compensation process is the growth mechanism of the layer. The impurities set free from the substrate by chemical etching processes rebuilt into the growing layer. In addition formation of EL2 centres may be initiated by As rich gas phase composition following the in‐situ etching.
Microhardness Anisotropy and Slip Systems in Biphenyl
Authors: Marwaha R. K. , Shah B. S.
Published: January 2007

The results of a study of the variation of hardness with load on the (001), (010), and (100) surfaces of biphenyl using the microindentation technique are presented. The microhardness anisotropy due to plastic deformation is explained in terms of the possible slip systems in biphenyl.
Quench Hardness Anisotropy of Rhombohedral Crystals: Calcite
Authors: Joshi D. R. , Pandya J. R.
Published: January 2007

Variation of microhardness with orientation of indenter (A) and quenching temperature Tq is studied on freshly cleaved surfaces {100} of natural rhombohedral crystals of calcite by producing Knoop indentations for various applied loads. The relation between hardness HA and quenching temperatures for the high loads (40–80 g) is graphically established. It also depends on the crystal orientation. The anisotropic indices are also determined.
Elastic Constants of Crystals from X‐ray Coherent Scattering Data. Dedicated to Professor Hermann NEELS on the occasion of his 80th birthday
Authors: Sirota N. N.
Published: January 2007

The X‐ray diffraction method for determining the elastic constants Cij and their temperature dependence using the Bragg reflection intensity is discussed.
Plastic Deformation of Cesium Iodide Single Crystals at High Temperatures
Authors: Urusovskaya A. A. , Demchenko V. V.
Published: January 2007

The plastic deformation of CsI crystals of three crystallographic orientations 〈100〉. 〈110〉. and 〈111〉 at temperatures from 423 to 773 K (0.5 to 0.86Tm) and strain rates from 2 × 10−3 to 10−5 s−1 is studied. Four‐stage stres‐strain curves were found, three stages being more and more distinct with an increase in temperature up to 623 K above which stage III prevails. For all the temperatures, strain rates and oreintations studied the superplasticity features (jerky flow, deformation localization, active dynamical recovery etc.) were observed. The thermal activatoin analysis has shown that the rate of high temperature deformation of CsI is controlled by dislocation climb limited in its turn by mobility of cation vacancies (quasiviscous creep).
An Isoperibolic Reaction Twin Calorimeter for Investigating Precipitation
Authors: Velich V. , Söhnel O. , Costa‐Bauzá A. , Kroupa M.
Published: January 2007

An isoperibolic reaction twin calorimeter is described and its application to studying precipitation is shown. This technique is suitable for determining both the total reaction enthalpy and also, in specific ranges of supersaturation, kinetics of the process. The total enthalpy of BaSO4 and CaC2O4 · H2O precipitation at 25 °C was determined as −16.2 and −18.1 kJ mol−1, respectively. The spontneous precipitation of these compounds affected by mixing reactant solutions together proceeds through initial surge of nucleation and fast crystal growth that steeply diminishes. No major wave of secondary nucleation during precipitation was observed.
On Measuring Impurity Absorption Spectra of Semiconductors by Photoacoustic Spectroscopy
Authors: Neumann H.
Published: January 2007

Theoretical relations are derived for the amplitude of the photoacoustic signal of a gas‐coupled cell for thick semiconductor samples including the influence of multiple reflections of light within the sample. It is shown that in the range of low absorption coefficients characteristic of impurity absorption spectra the sensitivity of the cell can be enhanced by using a highly reflecting metal as backing material. Numerical estimates for CuInSe2 are given to illustrate this effect.
On the Influence of Twinning Processes on Columnar Crystallite Growth in Electrodeposited Films
Authors: Shadrow V. G. , Tochitskii T. A. , Boltushkin A. V.
Published: January 2007

An investigation of columnar crystallite growth during the electrodeposition of fcc Ni and hcp Co‐W films has been made. It has been shown that the twinning processes not only promote the transformation of the initial orientation to the growth texture, but also lead to the change of the orientation of long columnar axes, the twinning processes in the fcc metal films exerting more significant influence on the columnar growth character than in the hcp ones.
Structure of a Manganese (II) Complex Containing Saccharin and 1,10‐Phenanthroline: [Mn(Sacch)2(o‐Phen)2(H2O)2] · H2O
Authors: Jianmin Li , Huidong Chen , Qiangjin Wu , Xintao Wu
Published: January 2007

The X‐ray crystal structure of the mononuclear manganese(II) complex containing saccharin and 1,10‐phenanthroline, [Mn(Sacch)2(o‐Phen)2(H2O)2] · H2O, is reported. The manganese atom has a geometrical structure of hexa‐coordinated distorted octahedron, saccharins interact with the central atom through water molecules.
The Epitaxial Orientation of Al on Si
Authors: Tempel A. , Büschel M. , Gantz T.
Published: January 2007

It is shown that the epitaxial growth of Al on Si {111} favours the epitaxial relation
{111} Si ‖ {100} Al; 〈110〉 Si ‖ 〈110〉 Al
instead of the more expected relation
{111} Si ‖ {111} Al; 〈110〉 Si ‖ 〈110〉 Al.
The elastic energy density of the epitaxial layer in the first case mounts to about 40% of that belonging to the second relation. The calculation of the elastic energy density in both cases is based on the assumption of pseudomorphical epitaxial film overgrowth between deposit and substrate supercells.
Polytypism in MX2 Compounds: A Case of Mixed Equilibrium Phases
Authors: Ahmad Shandar , Wahab M. A.
Published: January 2007

Classical polytypism in MX2‐type compounds has been investigated. It has been established that polytypism can be understood, not as the case of independent stacking of A, B, or C layers but in terms of basic structural units, the most stable and only equilibrium phases of the given compounds. Other polytypes are formed only as a result of various equivalent positions that these units can take a given cell height. A criterion to predict whether a given compound would exhibit polytypism is also suggested. Several problems in applying ANNNI and other spin models to polytypism have been pointed out and a modified Hamiltonian is suggested.
Growth and Characterisation of Potassium Pentaborate Single Crystals
Authors: Raja C. Ramachandra , Gobinathan R. , Gnanam F. D.
Published: January 2007

Single crystals of potassium pentaborate were grown by the solution growth method. The grown crystals were characterised by optical transmission spectrum, differential thermal analysis, and thermogravimetric analysis. The coefficient of thermal expansion was also determined and the results discussed.
Optical Absorption Spectrum of Cu2+ Ions in Lithium Sodium Potassium Sulphate Single Crystal
Authors: Kumar R. Rama , Reddy B. C. Venkata
Published: January 2007

Single crystals of Copper‐doped Lithium sodium potassium sulphate were grown at room temperature. The optical absorption spectra were recorded at room and liquid‐nitrogen temperatures. The observed absorption bands have been attributed to an ion of Cu2+ in tetragonal symmetry with 2B1 as the ground state. A successful interpretation of all the observed bands have been made by taking into consideration spin‐orbit coupling associated with a tetragonal field.

The crystal field parameters derived are Dq = 1045 cm−1, Ds = 1352 cm−1 and Dt = 457 cm−1.
The Effects of Polymeric Additives on the Crystallization of Compounds Found in the Evaporator Scales of Australian Sugar Mills (I), Compositions of the Scale Deposits
Authors: Doherty W. O. S. , Crees O. L. , Senogles E.
Published: January 2007

The composition of scales formed in multiple evaporator units at three Australian sugar mills have been determined using X‐ray fluorescence (XRF), high performance liquid chromatography (HPLC), X‐ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA) and other analytical methods. The composition of the scales formed in each mill have been found to be significantly different and to depend on whether they originated from early or later stages of the evaporation process. Calcium oxalate (present as the di and monohydrate) was identified as a major component of the scales from one mill but was found to be only a minor component of the scales from the other two. The latter were shown to contain two or more forms of calcium phosphate as dominant phases. Amorphous or crystalline silica was found to be present in most of the scales examined.
Infrared Lattice Vibrations of CdGa2Te4
Authors: Neumann H. , Moise E. , Schwer H. , Krämer V.
Published: January 2007

Infrared reflectivity spectra of CdGa2Te4 crystals are measured at room temperature in the wavenumber range from 180 to 600 cm−1 for the polarization directions E ⊥ c and E ‖ [111]. The frequencies of two E modes and two B modes are derived from the spectra. The frequencies of the modes with highest energy compare well with those of the corresponding modes in CuGaTe2 and AgGaTe2 which confirms the sphalerite‐like nature of these modes.
Analysis of the Load Dependence of Indentation Experiments
Authors: Berg B. , Grau P.
Published: January 2007

In most cases of microhardness Kick's law of similarity is unvalid. Therefore different equations were supposed to describe the real dependece of load and diagonal length of an indentation. These equations are independent from one another and it is not allowed to combine these. It is shown by means of experimental values from Joshi and Pandya that in a limited range of load different types of these equations can be used without a possibility to decide which gives a better description.
Ultrasonic Studies of Natural Oils and Fats of Plant Origin
Authors: Murthy V. R. , Kumar K. V. Siva , Reddy R. N. V. Ranga , Murthy Y. Narasimha
Published: January 2007

Investigations of specific volume and ultrasonic velocity as a function of temperature are carried out in different natural oils and fats of plant origin. From these studies it is found that the mango kernel fat exhibits liquid crystal‐like molecular order at T < 317 K. Various ultrasonic parameters like adiabatic compressibility, molar sound velocity, molar compressibility, van der Waal's constant, and intermolecular free length are evaluated. The variation of these parameters with temperature is also studied and the results are discussed critically.
Crystal Structure Analysis at Normal and Low Temperature Conditions
Authors: Luger Peter
Published: January 2007

80 years after its discovery X‐ray diffraction presents itself as an outstanding method in structure determination which allows the most safe and accurate geometrical data of chemical structures to obtain compared to most other experimental methods. The major innovations in the recent past and the present state of crystal structure analysis are described together with some examples in inorganic and organic chemistry, including the use of synchrotron radiation.

A variety of additional applications can be considered if the diffraction experiment is executed at low temperatures. Nitrogen gas stream devices and closed cycle helium cryostats are compared and their advantages/disadvantages are discussed. Finally some applications such as low temperature crystallization, temperature dependent structure analysis down to 20 K and deformation density work are illustrated.
Morphology of BBO Crystals and their Inclusions
Authors: Zhong W. Z. , Hong H. C. , Lu Z. P. , Zhao T. D. , Hua S. K. , Tang D. Y. , Zhao Q. L. , Zeng W. R. , Lin X.
Published: January 2007

This paper reports on the morphology and inclusions in the low temperature phase barium metaborate BaB2O4(BBO) crystal grown by an improved flux pulling method. The morphology of ideal BBO crystals and the relationship between the faces and the growth rate are given. The result that BBO has the symmetry L33P and belongs to the space group C3v−3m can therefore be concluded. It is found that the polarity of the BBO crystal along the Z (or c) axis has a visible influence on the morphology. The investigation of the inclusions in BBO crystals shows that these have a six‐fold symmetry which corresponds to the extension of flute‐like facets. It is also found that most of the inclusions have a regular geometric figure and can be regarded as the negative‐crystal structure which is due to the internal growth mechanism.
Microstructure and Texture Formation in Vacuum‐deposited Silver Films
Authors: Grantcharova E. , Dobrev D.
Published: January 2007

The role of the recystallization in the processes of microstructure and texture formation of silver films is compared for films: 1) deposited at high substrate temperatures (up to 720 K) and slowly cooled or quenched to room temperature; 2) deposited at room temperature and annealed at high temperatures. The grain growth distribution curves and the texture perfection are analysed. It is shown that the recrystallization processes taking place both during the slow cooling and during the annealing of the films lead to a formation of identical film structure with lower degree of texture perfection than in the case of quenched films.
Monte Carlo Simulation of Transient CSD in a Continuous Crystallizer under Stochastic Dispersion Effects
Authors: Dey Avijit , Gupta Bhaskar Sen
Published: January 2007

Monte Carlo simulation is a very powerful tool for simulation of transient and steady state crystal size distribution (CSD) in a continuous crystallizer under stochastic dispersion effects. In the present work, transient CSD in a continuous crystallizer has been reported when shape factor and growth rate dispersions conform to normal distribution. For the steady state run, the algorithm reported by Sen Gupta and Dutta elsewhere has been used to validate the results obtained in the present work when the steady state is reached.
The Crystal and Molecular Structure of 1,18‐dibromooctadecane
Authors: Nakamura N. , Yamamoto T. , Kobayashi H. , Yoshimura Y.
Published: January 2007

The crystal and molecular structures of 1,18‐dibromooctadecane are determined precisely by X‐ray diffraction method. The results obtained are as follows: empirical formula, C18H36Br2, formula weight Mr = 412.27, crystal system, monoclinic, space group, P21/n, lattice parameters, a = 5.496(1), b = 5.403(1), c = 34.374(4) Å, β = 94.50(1)°, volume of unit cell, V = 1017.6(3) Å3, Z value, Z = 2, calculated density, Dx = 1.346 g/cm3, wave length of X‐ray, λ(CuKα) = 1.5418 Å, absorption coefficient, μ(CuKα) = 49.64 cm−1, F(000) = 428.00, temperature, T = 293 ± 1 K, R factor, R = 0.052, weighted R factor, Rw = 0.078 for 1019 unique observed reflection [I > 3σ (I)]. There are no unusual bond distances or angles. The structure obtained here is quite similar to that of 1,12‐dibromododecane.
Structural and Thermal Characterization of Zeolite Type X Modified by Successive Ion Exchange with Cobalt and Manganese Cations
Authors: Sarbak Zenon
Published: January 2007

The successive exchange of Co2+ and Mn2+ with NaX zeolite has been studied. Influence of the above cations on crystalline structure of zeolite type X and its thermal stability has been shown on the grounds of X‐ray diffraction, differential thermal analysis, and infrared spectroscopic measurements.
Ionic Conductivity of KBrKI Mixed Crystals
Authors: Kumar G. S. , Bhimasankaram T. , Prasad G.
Published: January 2007

Ionic conductivity studies have been made on the mixed KBrKI single crystals in the temperature region 150°–650 °C. The log σ versus 1/T plots indicate four different regions. The activation energies associated with different regions have been calculated and its variation with the composition of the mixed crystals is reported. The results obtained are correlated with the theoretical values calculated using Lidiard theory. An attempt is made to understand the results.
Semiconducting Properties of TI2Te3 Single Crystals
Authors: Hussein S. A. , Nassary M. M. , Gamal G. A. , Nagat A. T.
Published: January 2007

Electrical conductivity and Hall effect measurements were performed on single crystals of TI2Te3 to have the general semiconducting behaviour of this compound. The measurements were done at the temperature range 160–350 K. All crystals were found to be of p‐type conductivity. The values of the Hall coefficient and the electrical conductivity at room temperature were 1.59 × 103 cm3/coul and 3.2 × 10−2 ω−1 cm−1, respectively. The hole concentration at the same temperature was driven as 39.31 × 1011 cm−3. The energy gap was found to be 0.7 eV where the depth of impurity centers was 0.45 eV. The temperature dependence of the mobility is discussed.
STGR Model and Relation between Growth Rate and Polytypism
Authors: Ahmad Shandar , Wahab M. A.
Published: January 2007

Effect of crystal growth rate on polytypism has been explained using STGR model. It has been suggested that during the process of growth, polytypes are formed from a suitable combination of basic units in accordance with the rate of growth. At a slower rate the most probable polytype is predicted to be different from the one at faster rate.
Silicon Epitaxial Layers with Non‐Uniform Doping Profiles (I). The Model Parameters' Adjustment
Authors: Halaj J.
Published: January 2007

The non‐uniform doping profiles may prove useful for some semiconductor devices instead of the uniform ones. In the paper the doping mechanism of silicon epitaxial layers in the SiCl4H2PH3 system is investigated. The epitaxial doping profile simulation program is developed based on the Wong‐Reif trapping model and taking into account also the difference between dopant profile and the charge carrier profile. The three unknown parameters of the Wong‐Reif model are found with the aid of the simulation program.
Synthesis and Characterization of the Levyne‐like Structure SAPO‐35, Prepared with Cyclohexylamine as Templating Agent
Authors: Lohse U. , Vogt F. , Richter‐Mendau J.
Published: January 2007

The microporous aluminophosphate SAPO‐35 with the levyne‐like structure was prepared hitherto only with quinuclidine as templating agent. In this paper it is shown that also cyclohexylamine can be used for the synthesis of SAPO‐35. The samples were characterized by X‐ray diffraction, thermal analysis, adsorption isotherms, and micrographs. These investigations confirm the few data reported on SAPO‐35 and give further informations. The number of acid sites (Brönstedt centres) was determined from the differential molar heat of chemisorption of NH3 to three per unit cell.
Mixed Chalcopyrites as Useful Solar Cell Materials
Authors: Samanta L. K. , Ghosh D. K. , Ghosh P. S. , Chatterjee S.
Published: January 2007

I1n view of the present global energy crisis the advent of the ternary chalcopyrites with some important useful properties stimulate us to study these compounds together with their mixed versions with a view to find their suitability as efficient solar cell materials. We finally selected out a few promising materials, as some of them have desirable characteristics and satisfy the stringent requirements for photovoltaic energy conversion.
The Crystal and Molecular Structure of Mesogenic Malonates
Authors: Körner H. , Zugenmaier P.
Published: January 2007

The crystal and molecular structures of diethylene‐6‐[4‐(4′‐nitrophenylazo)phenoxy]dodecylmalonate (12 PhNO2) and ‐propylmalonate (3 PhNO2) were determined with CuKα to a = 19.235(5) Å, b = 7.620(1) Å, c = 22.400(4) Å; α = 90°, β = 103.27(1)°, γ = 90°; space group P21/c for 12 PhNO2 and a = 6.797 (6) Å, b = 7.756 (8) Å, c = 22.74(2) Å; α = 81.48(7)°, β = 88.29(7)°, γ = 68.10(9)°; space group P1 for 3 PhNO2. Refinement with 1130 observed reflections (> 3σ) for 12 PhNO2 and 1615 for 3 PhNO2 leads to R (12 PhNO2) = 5.8% and R(3 PhNO2) = 4.4%.

The molecular conformation in the crystalline state is the most extended trans conformation for both compounds. On rapidly cooling from the isotropic melt, 12 PhNO2 shows a smectic A‐phase. In agreement with prior investigations on polar mesogens, the molecules arrange in an antiparallel packing. The azo‐mesogen is nearly coplanar with the alkoxy spacer up to the branching atom. The low molecular weight malonates investigated may serve as model compounds for side‐group liquid crystalline polymers.
Study of film crystallization kinetics initial stage by Monte Carlo simulation
Authors: Aleksandrov L. N. , Bochkova R. V. , Kiselev G. B. , Entin I. A.
Published: January 2007

The Monte Carlo Simulation has been used for studying the initial stage characteristics of film crystallization during the layer‐by‐layer film growth by two‐dimensional nucleation. It is shown that the non‐monotonous changes of the growing film perimeter and mass correspond to the reflection intensity oscillation from the growth surface. The observed changes of the overgrowing part of the surface are in agreement with the probability‐statistical calculations. The vizualization of surface relief changes during the growth process under different conditions has been provided.
Influence of size on the supercooling in the crystallization of small particles in Bismuth island films
Authors: Gladkikh N. T. , Larin V. I. , Maiboroda S. A.
Published: January 2007

There has been measured the crystallization temperature of supercooled Bi particles versus their size in the 3–100 nm range in island films on amorphous carbon substrates. Crystallization temperature is found to decrease with particle size decreasing and the supercooling vanishes for particles of 2–3 nm in diameter. The results obtained are analyzed in the frame of the classic theory of crystallization.
DCXS and RHEED characterization of effectiveness of annealing implanted Si crystals by using pulsed UV excimer laser and sample scanning technique
Authors: Auleytner J. , Kozankiewicz B. , Regiński K.
Published: January 2007

In the experiment (111) oriented silicon plates were implanted with 80 keV Ge ions (dose 5 × 1015 cm−2) and with 150 keV Kr ions (dose 5 × 1015 cm−2). Then the samples were annealed with the pulsed excimer laser by using the sample scanning technique. The effectiveness of the annealing has been analyzed by means of double crystal X‐ray spectrometry (DCXS) and reflection high energy electron diffraction (RHEED). The results of the experiment show that the applied technique of annealing considerably improves the perfection of the structure of the implanted silicon crystals.
Elastic properties of the dithionates Na2S2O6 · 2 H2O, K2S2O6, Rb2S2O6, CaS2O6 · 4H2O and SrS2O6 · 4 H2O
Authors: Haussühl S.
Published: January 2007

Single crystals of the title compounds having optical quality and dimensions of several cm were grown from aqueous solutions. The elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates. The true point symmetry of K2S2O6 and Rb2S2O6, which is screened by a hexagonal hypermorphy, could be clearly revealed to be trigonal (32) by the existence of the elastic constant c14. In the case of CaS2O6 · 4H2O and SrS2O6 · 4H2O the constant c14 of the specimens appeared too small to confirm the trigonal symmetry group required from electrooptic and non‐linear optic effects unambiguously.

The isotypy of K2S2O2 and Rb2S2O6 as well as that of CaS2O6 · 4H2O and SrS2O6 · 4H2O is confirmed by their elastic behaviour. The mean elastic stiffness of dithionates is closely related to that of the corresponding sulphates. In the vicinity of the second‐order phase transition of K2S2O6 near 235 K weak anomalies of the temperature derivatives of the longitudinal elastic stiffnesses are observed.