bluuebunny/crossref_metadata_2025 huggingface dataset:
Annealing of electron irradiated GaP studied by positron lifetime technique
Authors: Sen Gupta A. , Moser P. , Corbel C. , Hautojärvi P. , Sen P.
Published: January 2007

GaP single crystals were irradiated by 3 MeV electrons at 20 K to a dose of 4 × 1018 e/cm2. An isochronal annealing in temperature region 77 ÷ 650 K followed the irradiation. Positron lifetime measurement indicated the presence of irradiation‐induced vacancies in Ga sublattice. The vacancies disappeared at two stages observed at temperatures 200 ÷ 300 K and 450 ÷ 550 K.
The current understanding of epitaxial silicon doping in the light of modelling and theory development (VI) autodoping as a special mode of dopant incorporation
Authors: Kühne H.
Published: January 2007

A consequent application of dopant incorporation theory to epitaxial silicon layer growth above buried layer regions explains the formation of an exponentially decaying dopant profile not only above that buried layer but also beyond of it. Taking into account desorption of dopants only and and neglecting readsorption of dopants on buried layer regions allows one to describe both vertical redistribution autodoping and lateral autodoping by the well known exponential expression that originally has been derived by Reif et al. in order to describe intended non‐steady state doping behaviour and later applied to lateral autodoping by Wong and Reif. Doping incorporation theory also explains the formation of a near‐equilibrium surface coverage with adsorbed dopants outside of buried layer during a preepitaxial baking process.

Different dopant sources contributing to autodoping are characterized by different time constants. In this connection the adsorbed layer model derived by Tabe and Nakamura could be related to the action of two different dopant sources of autodoping where one of the two is characterized by a time constant being nearly infinite in number.
Interatomic interaction aspect of phase transition in AgInS2 crystals
Authors: Vaipolin A. A. , Rud Yu. V. , Rozhdestvenskaya I. V.
Published: January 2007

The structural parameters of two modifications of AgInS2 are determined. The geometrical model of phase transition is discussed. Crystallochemical comparison reveals the absence in the two modifications of significant differences in atomic interactions. The changes in atomic interaction with the temperature increase and the role of dynamical changes in phase transition are discussed.
Angular correlation studies of thin metal films
Authors: Aravin L. G. , Valiev K. A. , Goldanskii V. I. , Novikov Yu. A. , Rakov A. V. , Filimonov M. K. , Shantarovich V. P.
Published: January 2007

Angular correlation of positron annihilation radiation is widely used in solid state physics studies (Goldanskii; Hautojärvi), in the defectoscopy of monocrystals in particular (Nielsen et al.). The interest to surface studies gave rise recently to very sophysticated and expensive method of positron beams (Goldanskii et al.). The recent study and recently published papers (Aravin et al.; Valiev et al.) demonstrate, however, that valuable information on surface properties can be obtained using the traditional angular correlation (AC) technique.
On segregation during crystal growth from a solution zone
Authors: Gille P.
Published: January 2007

The distribution in a mixed crystal A1−xBxC grown from an either (A, B)‐rich or C‐rich solution zone (e.g. travelling heater method or related techniques) is to be described by Pfann's zone melting function which depends on the segregation coefficient and a characteristic length. Using pseudobinary mole fractions x the characteristic length of the distribution function is not the actual length of the liquid solution zone but an effective zone length is to be regarded which may be considerably smaller or much bigger for C‐rich or (A, B)‐rich solutions zones, respectively.
Mechanism of dendritic side‐branches coarsening under isothermal conditions
Authors: Fedorov O. P. , Ovsienko D. E.
Published: January 2007

The process of dendritic branches transformation of succinonitrile and some other organic substances has been studied under the isothermal holding of two‐component melt. The dendritic branches have been shown to be separated from the steam in the specimen with the thickness comparable with the diameter of the dendrite. Dendritic structure coarsening observed in the bulk specimen is not associated with the separation of the branches. In the region of the concentration gradient the dendritic growth has been shown to result in partial dissolution of as‐crystallized material under the isothermal holding after the end of crystallization. This effect seems to result from the diffusionless growth in the two‐phase region of the phase diagram.
Specific heat and related properties of some AIIBIVC and AIBIIIC semiconducting compounds between 2 and 300 K
Authors: Bischof J. , Bohmhammel K. , Deus P.
Published: January 2007

From specific heat measurements of the ternary semiconducting compounds ZnSiP2, ZnSiAs2, CdGeAs2, CuGaSe2, and CuInTe2 Debye characteristic temperatures and standard entropy values are calculated within the temperature range from 2 to 300 K.
The role of argon in yttrium aluminates
Authors: Kvapil Ji. , Mánek B. , Perner B. , Kvapil Jos. , Becker R. , Ringel G.
Published: January 2007

Spectral properties of YAG and YAP grown in vacuum or under ArH2 protective atmosphere were compared. The latter contained small amounts of argon which was detected by a laser mass spectral analysis. Ar impurity evokes brown colour of unannealed crystals and strenghtens anomalous red colour of annealed (Particularly in O2) YAP crystals doped with Nd + Cr or Nd + Mo. The same red coloration of the doped YAGs is less stable.
On the dispersion of the refractive index in AIIBVI thin films
Authors: Łepek M.
Published: January 2007

We propose a new calculation following traditional methods for deducing refractive index from the fringe pattern of the transmission spectrum of a thin transparent CdS, ZnS, and ZnxCd1−xS film surrounded by nonabsorbing media. The error in the refractive index measurements is 4–5%. We have found that polycrystalline CdS, ZnS, and ZnxCd1−xS evaporated films have refractive index different from those of single crystal material.
Metalorganic chemical vapour deposition of oriented ZnO films
Authors: Kaufmann Th. , Fuchs E. , Webert M.
Published: January 2007

Thin uniform films of ZnO could be obtained by MOCVD using Zn(CH3)2‐THF adduct and H2O as reactants. The film growth was carried out at atmospheric pressure. A vertical resistance‐heated cold‐wall reactor system was used. Highly c‐axis oriented ZnO films being very smooth and having a low resistivity were grown on (100)Si and (100)Si/SiO2 under certain conditions. Epitaxial growth could be achieved on (1102)‐sapphire. The dependence of the properties of the films on the growth conditions was investigated.
GaPAlxGa1−xP heterostructure edge coupling waveguides for hybrid integrated optic devices
Authors: Díaz P. , Gonzalez C.
Published: January 2007

In this paper we present the performance of GaPAlxGa1−xP heterostructure waveguides for integrated optic hybrid devices. The waveguide layer is graded with a parabolic refractive index profile for the light emission of a DHGaAs semiconductor laser. The waveguide heterostructure performed allows to couple at it edge crossection semiconductor laser or photodetector as well as fix or solder them on the same substrate on which the heterostructure layers were deposited.

The heterostructure layers were grown by liquid phase epitaxy and the heterostructure waveguide was performed by means of etching technics specially developed for this purpose.

Both, the growth procedure, as well as the etching technics are described. The results achieved are shown in curves and photographs, taken on a scanning microscope.
A study of ferroelectric domain patterns in orthorhobic KNbO3 with optical microscopy
Authors: Jun Chen , Wen‐shan Wang , Qi Li , Duan Feng
Published: January 2007

Ferroelectiric domain patterns in natural surface layers of Czochralski as‐grown crystals are very complicated. The inner domain patterns are comparatively simple and consist of a regular arrays of so‐called thin lens‐like 90° domains. Only few inner 60° and 120° domains crossing the 90° domain arrays are observed. The inversion or 180° domains are shape‐like separated islands. The 60° microdomains are easily introduced into the surface layers during the specimen processing. There are some elastic interactions between the different kinds of ferroelectric domain walls, the orientations of which are in good coincidence with the theory proposed by Janovec.
Nitrido‐phthalocyanine‐rhenium (V) structure and absorption spectra
Authors: Mrwa A. , Giegengack H. , Starke M.
Published: January 2007

The crystal structure of nitrido‐phthalocyanine‐rhenium (V) has been determined from X‐ray diffraction date. The crystal data are: C32H16N9Re (tetragonal), a = 1.775 nm, c = 1.386 nm, Z = 4, ϱ = 2.23 g cm−3. Optical and infrared absorption spectra have been measured on sublimated films and compared with the corresponding spectra of other metal phthalocyanines.
On the crystal structure type of 2 CsCl · CoCl2 · 2 H2O
Authors: Balarew Christo , Tepavitcharova Stefka
Published: January 2007

The following three‐component systems have been studied: CsClMnCl2H2O at 25 °C; 2 CsCl · CuCl2 · 2 H2O—2 CsCl · CoCl2H2O at 10 °C and 2 CsCl · MnCl2 · 2 H2O—2 CsCl · CoCl2H2O at 25 °C and 10 °C. It was established that Co2+‐ions do not substitute isodimorphously the Cu2+‐ions in the tetragonal salt 2 CsCl · CuCl2 · 2 H2O, whereas in the case of the triclinic salt 2 CsCl · MnCl2 · 2 H2O they can substitute isodimorphously the Mn2+‐ions.

The theoretical considerations supported by the results obtained allow to predict the existence of the double salt 2 CsCl · CoCl2 · 2 H2O as well as the type of its crystal structure — triclinic, space group P1.
Combined surface analytical and electrochemical investigations of RuTiSn mixed oxide electrocatalysts
Authors: Wagner N. , Kühnemund L.
Published: January 2007

Using a galvanostatic oxygen exposure, it can be shown by XPS and SEM that admixtures of Sn (2 at.%) to RTO anodes inhibit the corrosion of both the bulk ruthenium species and the titanium substrate interface. The inhibitor effect is strongly dependent on the Sn segregation to the surface region blocking the channels of oxygen diffusion in incoherent active layers for Cl2 evolution.
An AES/XPS study of oxygen involved reactions on InSb
Authors: Wolf B. , Zehe A.
Published: January 2007

The oxidation of ion‐etched InSb(110)‐cleavage planes was investigated by means of AES and XPS, respectively. Whereas the sticking coefficient of oxygen at indium sites was found to reach a saturation value after slight ion bombardment, the oxygen uptake rate of antimony remains low (sticking probability in the 10−7 range) with raising ion dose to a point where a drastical change in oxidation behaviour occurs at ion doses in the 10−2 As · cm−2 range. Then indium and antimony are nearly simultaneously oxidized with sticking coefficients of roughly 10−3. Cluster formation is discussed as one possible mechanism to explain the experimental findings. Adsorption experiments on disordered surfaces can contribute to a better understanding of surface reactions during gas phase growth of single crystals, since the in‐growth situation of the top layer of the latter is far away from the ideal situation that is prepared by in situ cleaving only.
The influence of titania content on structure and properties of spherical mixed silica/titania particles
Authors: Bräuer K. , Hörhold H.‐H. , Klemm E. , Krah S. , Rudakoff G. , Vogelsberger W.
Published: January 2007

Spherical mixed silica/titania particles are prepared from silica/titania sol by an ultrasonic vibrator. The titania content of the samples varies from pure silica to a titania mole fraction of 0.31. Narrow size distributions with most frequent particle diameter of about 1 μm are obtained. Specific surface area and pore volume, mean pore radius as well as the meso pore size distribution are influenced by titania content. The spheres are composed of both silica and titania homogeneous distributed as it is indicated by scanning electron microscopy. X‐ray diffraction studies show that the particles must be considered amorphous. Structural modifications of the framework are detected. Samples with varying refractive index may be prepared.
Phase relations and crystal growth of YBa2Cu3O7−δ in the system YO1.5BaOCuO
Authors: Fischer K. , Hergt R. , Linzen D.
Published: January 2007

The liquidus face of the system YBa2Cu3O7−δBaCuO2CuO was investigated by DTA. We found liquidus temperatures below 1000 °C only in a narrow region with small yttrium oxide content near the eutectic of the system BaCuO2CuO. The crystallization path of crystal growth experiments is discussed and the principle structure of the phase diagram is derived. Single crystals are grown being superconductive after thermal treatment in oxygen atmosphere.
Diffusive‐convective mass transport of HgI2 in closed ampoules
Authors: Laskowski Jarosław , Przyłuski Jan , Conder Kazimierz
Published: January 2007

The mass transport rate of HgI2 in closed ampoules with the addition of He, Ar or Xe at different pressures (20–200 Torr) was gravimetrically measured. Diffusive and convective mass fluxes in the systems studied were calculated according to vapour transport models. The influence of technological parameters, i.e. temperature, pressure, kind of added gas, and ampoule diameter, on the mass transport of HgI2 vapour was studied. Mechanisms of vapour flow in the applied experimental conditions are discussed.
Temperature dependence of the photoconductivity in CuInTe2 single crystals
Authors: Tomlinson R. D. , Neumann H. , Slifkin M. A. , Al‐Saffar I. S. , Al‐Rahmani A.
Published: January 2007

The temperature dependence of the steady‐state photoconductivity of as‐grown and annealed CuInTe2 single crystals was measured in the range from 77 to 300 K. A model with two electron trapping centres is proposed to explain the experimental data.
The crystal structure of zinc azide · 2‐methylpyridine at 98 K
Authors: Mautner Franz A. , Kratky Christoph
Published: January 2007

The crystal structure of the title compound has been determined by single crystal X‐ray diffraction methods at 98 K. Zinc azide · 2‐methyl pyridine crystallizes in the space group P1 with a = 6.028(2) Å, b = 7.610(3) Å, c = 10.052(4) Å, α = 92.81(3)°, β = 101.08(2)·, γ = 94.64(3)° and Z = 2. Least‐squares refinement gave an R value of Rw = 0.039 for 2096 observed reflections.

Each zinc atom is surrounded by four nitrogen atoms of different azide groups and one nitrogen atom of the pyridine adduct in a distorted trigonal bipyramidal fashion. The ZnN5‐polyhedra share common edges to form chains along the crystallographic a‐axis.
On the investigation of dopant boundaries in silicon device structures by means of SEM‐EBIC
Authors: Hoppe W. , Kittler M.
Published: January 2007

The capabilities to study the geometrical construction of silicon devices by the technique of the electron beam induced current (EBIC) are reviewed with particular emphasis to the 2‐dimensional determination of dopant boundaries (p‐n junctions) including a discussion of demands for such investigations from a microelectronic point of view. The investigations of buried layers and MOS short‐channel transistors are outlined. As a substantial topic the preparation of electrically stable surfaces at cleaved samples is discussed and an example of the possibility of cross‐sectional analysis for junction delination is briefly given.
Structural characteristics of some lanthanide violurate complexes
Authors: Awadallah R. M. , Farag I. S. Ahmed , Gad A. A. M.
Published: January 2007

The magnetic moments and the electronic spectra of violurate complexes of Ce3+, Pr3+, Pr4+, Nd3+, Sm3+, Eu3+, Gd3+, Ho3+, Er3+, and Yb3+ have been investigated. The solid complexes are paramagnetic and have magnetic moment values near to the ground state values of the free ions. Few cases differ, since there exist possible electronic transitions (4f → 5d) in case of Ce3+ complexes and (f → f) for Ho3+ and Dy3+ complexes. The magnetic measurements in connection with the electronic spectra were used to decide the different electronic structural configuration of elements and hence the configuration of the coordination polyhedra around the central metal ions of the investigated complexes.
On the initial stage of plastic deformation of sulphur‐doped gallium phosphide
Authors: Boehnke O. , Paufler P.
Published: January 2007

The overall deformation behaviour between room temperature and 1000 K has been investigated by bending and uniaxial compression at small strains ≦ 0.1%. Ductile‐to‐brittle transition temperature was found at 44% of the melting point. Dislocations are generated mainly at surface irregularities. Whereas screw dislocations predominate at the beginning 30° and 60° segments become more important after cross slip and interaction of different slip systems.
Comprehensive characterization of CdTe and (Cd, Zn)Te single crystals by a chemical etchant
Authors: Wermke B. , Mühlberg M. , Engel A. , Rudolph P.
Published: January 2007

Using a known chemical etchant low‐ and high angle boundaries and lamellar twins can be seen on CdTe and (Cd, Zn)Te crystal ingots as a whole as well as on slices with naked eyes. Also the polarity of {111} samples can be determined in this way. Etch pits are produced on cut and polished surfaces independent of their crystallographic orientation. A new modified etchant was used to study the low angle subgrain structure on (111)Te surfaces.
Numerical analysis of various heat input regimes applied to liquid encapsulated Czochralski crystal growth
Authors: Böttcher K. , Krüger A. , Schleusener B.
Published: January 2007

By the hand of a stationary system‐oriented model of the InP crystal growth (LEC) various regimes of heat input into the melt are demonstrated. They are compared by regarding their influence over the maximal temperature of the melt, the curvature of the crystallization front, and the temperature of the crystal at the end of the boric oxide.
Crystallization kinetics and phase transformations of zinc‐ and cadmium diphosphide films
Authors: Denis V. A. , Sheleg A. U. , Unyarkha L. S.
Published: January 2007

The kinetics of isothermal crystallization of amorphous ZnP2 films in the temperature range from 730 to 810 K and amorphous CdP2 films between 630–770 K has been investigated. The kinetic curves of isothermal transformation of amorphous films into crystalline ones have been obtained. For ZnP2 the transformation occurs as follows: amorphous films → α‐ZnP2 (tetragonal modification) → β‐ZnP2 (monoclinic modification). For CdP2 – amorphous films → γ‐CdP2 (cubic modification) → β‐CdP2 (tetragonal modification). From the experimentally determined kinetic curves the stability diagrams for ZnP2 and CdP2 films have been plotted. The most stable modification in the investigated temperature range are β‐ZnP2 and β‐CdP2 other ones are metastable. The values of effective energy of activation of transformation have been determined.
Time‐dependent trench profile formation during RIE‐processing of silicon with CCl2F2‐gas mixture
Authors: Kühne H. , Glück B.
Published: January 2007

The formation of the three main types of trench profiles (step‐like profile and trapez‐like profile the small side down or up, respectively) and their time‐dependent development during trench etching have been explained by taking into consideration not only the vertical etch rate and the factor of etching anisotropy given by mask undercutting but also the additional factor of etching anisotropy given by applying the definition to the bottom rim of the trench. Concidering both time‐and depth‐dependence of etching anisotropy the formation of projecting brims within a trench can be interpreted, too.
Bulk flow phenomenon in Czochralski configuration caused by low frequency vibrations
Authors: Zharikov E. V. , Prihod'Ko L. V. , Storozhev N. R.
Published: January 2007

The described experimental results demonstrate that vibrations can essentially affect the melt flow in growth processes. The existence of vibrational convection must be taken into account in interpreting the results of using the vibrations in crystal growth processes (IZERGIN et al.; LANGANECKER, FRANDSEN; NIKITINA et al.; WITT, GATOS). Vibrational convection opens new advantages to control the convective movement of melt and of interface shape during the crystal growth.
Trends in the microhardness of the CuBIIIC chalcopyrite compounds
Authors: Neumann H.
Published: January 2007

On the basis of a microhardness scaling law found for the AIIBIVC compounds and of the dependence of the microhardness on conductivity type and composition observed experimentally in CuInSe2 a model is proposed to describe the trends in the microhardness of the CuBIIIC compounds. The results are compared with experimental data and other microhardness estimates. It is found that most of the existing microhardness measurements can be interpreted within the model.
Intermolecular free lengths and odd‐even effect studies in certain alkoxy benzylidene butylanilines
Authors: Venkatacharyulu P. , Prasad K. S. R. , Rao J. V.
Published: January 2007

Using the thermoacoustic data the mean free lengths (Lf) as a function of temperature are estimated for certain members of the homologous series of alkoxy benzylidene butylanilines with m = 2 to 7 except 3, in their isotropic, mesophases as well as at and in the immediate vicinity of the phase transition temperatures. From these studies it is observed that the mean free lengths also exhibit odd‐even effect.
Hydrothermal analcime synthesis at 10 MPa isobar
Authors: Pechar František
Published: January 2007

Hydrothermal analcime synthesis at 10 MPa isobar and 100, 200, and 300 °C isotherms was performed. As synthesis initial components the minerals nepheline, albite, natrolite, jadeite, wairakite and the mixtures nepheline + albite and nepheline + natrolite were used. 1 M Na2SiO3, 1 M NaCl and 0.1 M NaOH (pH = 14, 7, 13) solutions were applied as the hydrothermal medium. On evaluating the synthesis products by means of X‐ray diffraction analysis and X‐ray microanalysis (EDAX) it was estimated that different analcime structural modifications originate especially at temperatures above 200 °C in neutral and alkaline medium from all the mentioned minerals. Analcime with a higher symmetry of the unit cell of crystals form at temperatures above 250 °C particularly.
Rheological behaviour of lamellar eutectic AlAl2Cu elaborated by induction heating
Authors: Bornier L. , Birocheau J.
Published: January 2007

This paper presents solutions to the experimental problems encountered in the elaboration of lamellar AlAl2Cu or fibrous AlAl3Ni eutectic samples using the Bridgman technique. The objective is to prepare samples for use in mechanical tests.

The investigation of the elaborated structures of AlAl2Cu (orientation, grain selection, shape of the solid‐liquid (S.L.) interface, interlamellar spacing λ…) can then be used to confirm the predicted behavior.

Creep tests under constant applied stress σ (from 2 to 5 · 107 N/m2) at temperatures from 300 to 450 °C show:

– that a stationary state exists (with constant strain rate

)

– the influence of an imperfect orientation

– the existence of a Bailey‐Norton creep law

= kσn. This law leads to the possiblity of finding a constitutive equation for high temperatures tests.
X‐ray two‐crystal diffractometer for testing of plane analyser crystals
Authors: Dressler L. , Wehrhan O. , Uhlig I. , Gütt R.
Published: January 2007

A two‐crystal diffractometer (TCD) for testing the mosaic structure of LiF crystals is presented. Peculiarities are the adapted sensivity (angular minutes), short measuring times, large registered areas and the possibility of application for various kinds of surface treatment.
Nonstoichiometry in steps on AB crystals (II). Extended treatments
Authors: Arnold H. , Fuchs G. , Kaufmann T. , Webert M.
Published: January 2007

Concentrations of atoms with different numbers of nearest neighbours, and of the kink and non‐kink positions between atoms in step fronts, have been calculated by two treatments. The results differ in the general case, but agree in cases with extreme nonstoichiometry as well as in nearly stoichiometric cases. With respect to the relevance of the model calculations, further investigations are necessary on step reconstructions, on the positions of stability limits of AB compounds in terms of step nonstoichiometry, and on the possibility of roughening transitions in connection with step nonstoichiometry.

With increasing nonstoichiometry in the steps, neighbouring kink positions, and the corresponding neighbour‐kink atoms become increasingly important. In contrast to this, the concentrations of double kink positions become smaller, and they vanish in the extreme cases where the PBC‐directed steps consist merely of A, or of B neighbour‐kink atoms. These concentrations are negligible in the extended model calculations at sufficiently low temperatures, together with concentrations of triple and further multiple kink positions.
Growth of Na2EuCl4 particles studied by means of their effect upon the yield strength of NaCl:Eu2+ crystals
Authors: Nowak‐Woźny Dorota
Published: January 2007

The hardening of NaCl crystals induced by the presence of europium ions has been systematically investigated in two regions of temperatures (below 343 K and above 473 K) as function of the aggregation and/or precipitation stage of the dopant. The kinetics of Eu2+ — clustering was followed by taking the δσ0(tan) — data at various annealing temperatures Tan. The results have been discussed in frames of the available theoretical models and compared with those obtained previously from OA‐ and ITC‐data.
Structural changes of some Fe‐containing layer silicates in the presence of as and S under hydrothermal conditions
Authors: Frank‐Kamenetskii V. A. , Kotov N. V. , Ernst R. , Goilo E. A.
Published: January 2007

Structural changes of chlorite, berthierine, biotite were investigated under hydrothermal conditions at pH2O = 100 MPa (1 kbar), T = 200–600 °C, run over 3 days with additions of AsS, NaCl, dolomite. The synthesis of pyrrhotine and arsenopyrite was detected at the expense of extraction of Fe from the structures of transforming layer silicates. The degree of the removal of Fe with the formation of sulphides depends on its being blocked up by a silicate surrounding. It grows in the sequence biotite‐chlorite‐berthierine.
Contribution to the Si doping of bridgeman GaAs
Authors: Siegel W. , Boudriot H. , Koi H. , Deus K. , Oettel O. , Schneider H. A.
Published: January 2007

GaAs: Si with different doping level was grown by the gradient freeze method. The crystals were characterized by structural, electrical and optical methods concerning especially the dependence of the epd and the compensation degree on the carrier concentration.
Thermal behaviour of natural heulandite crystals
Authors: Kumar P. K. Jeethendra , Rao P. Mohan , Setty D. L. R.
Published: January 2007

Thermal behaviour of natural heulandite crystals collected from Pashan area near Poona, India, is studied by employing static weight loss method (SWL), X‐ray diffraction, infrared spectroscopy, TG and DTA. The combination of these techniques provide better understanding of the structural modifications that occur in heulandite during thermal treatment. It is observed that heulandite structure is transformed from its ‘A’ phase to heulandite ‘B’ phase between 250–400 °C, and forms another intermediate metastable phase heulandite ‘C’ before the structure starts degrading above 500 °C.
Contribution to the determination of the entropy production for steady state eutectic growth
Authors: Wolczyński Waldemar
Published: January 2007

In order to find a generalized entropy production for steady‐state eutectic growth the entropy production per unit time and volume is to be determined. A relationship which expresses the entropy production per unit time and volume as a function of KRUPKOWSKI's equations is shown. It is in a qualitative accuracy with LESOULT‐TURPIN's theory. The above quantity is to be integrated over a distinguished volume of the unidirectionally solidified eutectic structure. A correlation between this volume and entropy production is discussed.
Dislocation internal friction and temperature dependence of yield stress in high‐purity molybdenum single crystals
Authors: Lebedev A. B. , Kardashev B. K. , Hofmann U. , Kaufmann H.‐J. , Schulze D.
Published: January 2007

High purity molybdenum single crystals (residual resistivity ratio ≈ 6 · 104) were studied by means of computer‐controlled internal friction technique at frequencies of about 100 kHz in the temperature range 6 to 300 K. The amplitude dependences of decrement were measured within the vibrational strain amplitude 10−7 to 10−4. It was established that the temperature dependence of ultrasonic amplitude providing a constant level of reversible dislocation deformation coincides well in relative units with the temperature dependence of the critical resolved shear stress at 20 to 180 K.
Some observations on melt‐grown cadmium iodide crystals
Authors: Chaudhary S. K. , Mohan D. , Trigunayat G. C.
Published: January 2007

Single crystals of richly polytypic compound cadmium iodide have been grown using a zone‐refining system. The frequent appearance of cracks in the grown crystals has been attributed to the thermal stresses and the presence of impurities. Structure of all the crystals has been found to be of the type 4H.
Evaluation of experimental parameters influencing the growth of large crystals of NaX zeolite
Authors: Kornatowski J. , Finger G. , Schmitz W.
Published: January 2007

Following the Charnell's procedure, the influence of materials, methods of preparation and changes in composition of the gel on the process of NaX zeolite crystallization have been investigated in order to find conditions providing both the growth of crystals as large as possible and also good reproducibility of the result. The experimental conditions used are detailed described.
Numerical simulation of MOVPE AlxGa1−xAs: Control of composition variation
Authors: Makarov Yu. N. , Zhmakin A. I.
Published: January 2007

Step response functions are introduced to describe the nonstationary mass transfer in MOVPE AlGaAs growth. The solutions of direct problem and inverse one of the control of solid solution composition are presented.
Formation of dislocation etch grooves in potassium bichromate crystals
Authors: Szurgot M.
Published: January 2007

The formation of etch patterns on dislocations in potassium bichromate (KBC) crystals has been studied. It was found that, depending on the relative position of a dislocation line with respect to the etching plane, either a groove or a groove associated with a pit or a pit alone are formed. A dislocation lying in the etching plane or not much inclined from it gives a groove or an array of etch pits. An inclined dislocation gives a groove connected with an eccentric pit and a normal one gives a centric pit. A dislocation to be revealed as an etch groove has to lie sufficiently close (<100 μ) to the observation plane.
Crystal and molecular structure of 17α‐acetoxy‐21‐hydroxy‐1,4‐pregnadiene‐3,20‐dione
Authors: Scharfenberg‐Pfeiffer D. , Megges R. , Bohl M. , Simon K. , Stopsack H.
Published: January 2007

The title compound 17α‐acetoxy‐21‐hydroxy‐1,4‐pregnadiene‐3,20‐dione crystallizes in the orthorhombic space group P 212121 with four molecules in the unit cell and the lattice parameters a = 10.950, b = 11.857, c = 15.634 Å. The crystal structure was determined by direct methods and refined by full matrix least squares calculations up to the discrepancy factor R = 0.050.

Die Titelverbindung 17α‐Acetoxy‐21‐hydroxy‐1,4‐pregnadien‐3,20‐dion kristallisiert in der orthorhombischen Raumgruppe P 212121 mit vier Molekülen in der Elementarzelle und den Gitterkonstanten a = 10,950, b = 11,857, c = 15,634 Å. Die Kristallstruktur wurde mit direkten Methoden bestimmt und mit der Methode der kleinsten Quadrate bis zu einem R‐Wert von 0,050 verfeinert.
The crystal and molecular structure of 5α,8α‐epidioxyergosta‐6,22‐dien‐3β‐acetate
Authors: Kutschabsky L. , Lindequist U. , Kretschmer R.‐G.
Published: January 2007

From the mushroom species Tricholoma populinum LANGE which shows interesting pharmaceutical effects the steroid 5α,8α‐epidioxyergosta‐6,22‐dien‐3β‐ol has been isolated. The acetate of this compound crystallizes in the monoclinic space group P 21 with two molecules in the unit cell of dimensions a = 19.788, b = 7.241, c = 9.914 Å, β = 103,97°. The final R‐value is 0.079 for 1082 reflections.
Effect of heat treatment on the optical absorption of tin diselenide thin films
Authors: Bhatt V. P. , Gireesan K. , Desai C. F.
Published: January 2007

Optical absorption measurements were made on tin diselenide thin films grown on glass substrates by thermal evaporation of stoichiometric bulk compound. In the as‐deposited films, optical absorption was dominated by an indirect transition at lower photon energies with a band gap of 1.4 eV. The direct allowed transition with a band gap of 1.62 eV was predominant at higher energies. Annealing the film at elevated temperatures resulted in the decrease of both the direct and indirect transition band gaps.
Kinetic investigations within the transition region from polyhedral to skeletal growth mode (II). Growth kinetics of the edge of the basal face of zinc single crystals under diffusion conditions
Authors: Iwanov D.
Published: January 2007

The growth kinetics of the edge of the basal face of zinc single crystals grown from a vapour phase under diffusion controlled conditions has been investigated. The growth of the basal edge with time at constant temperature and supersaturation and argon pressures between 5 and 250 Torr or in vacuum 1 × 10−6 Torr has been plotted. It is established that the length a of the edge of the {0001} face is changed with time t according to a linear and a parabolic dependence. The kinetic critical size ak is determined by the intersection point between the two parts of a2(t) curves. It is shown that the results from the kinetic investigations of the basal face edge are in qualitative agreement with the basic relationships characterizing the growth kinetics of crystals in a kinetic and a diffusion regime Experimental facts are presented (e.g. the parallel running a2(t) curves, etc.) which confirm the diffusion character of the observed transition of the basal edge of zinc single crystals from a kinetic regime to a diffusion growth mode.
Crystal and molecular structure of 5‐diazo‐2,2‐dimethyl‐4,6‐dioxo‐1,3‐dioxane and 5‐diazo‐1,3‐dimethylpyrimidin‐2,4,6‐trione
Authors: Ramm M. , Schulz B. , Thurner J.‐U. , Ulbricht M.
Published: January 2007

C6N2O4H6:Mr= 170.12, orthorhombic space group Pbca,a= 6.751(2),b= 13.669(4),c= = 16.845(4) Å,V= 1555(1) Å3,Dx= 1.248 Mgm−3,Z= 8,F(000) = 704, λ(moKα) = 0.71069 Å, μ = 1.1 mm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factorR= 0.039.

C6N4O3H6:Mr= 182.14, monoclinic space group C2/c,a= 17.726(8),b= 6.191(12),c= 16.062(6) Å, β = 117.59 (3)°,V= 1562 (1) Å3,Dx= 1.549 Mgm−3,Z= 8,F(000) = 752, λ(MoKα) = 0.71069 Å, μ = 1.2 mm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factorR= 0.056.
Band tail conduction in Zn‐doped GaAs
Authors: Neumann H. , Jacobs B. , Hörig W.
Published: January 2007

The electrical parameters of Zn‐doped GaAs liquid phase epitaxial layers are determined in the temperature range from 77 to 300 K by Hall effect and resistivity measurements. An analysis of the experimental data yields an ionization energy of 30.4 meV for the Zn acceptor in GaAs in the dilute limit of acceptor concentration. For the Mott transition a critical hole concentration of about 6 · 1017 cm−3 is estimated. It is found that the temperature dependence of the electrical parameters is essentially influenced by band tail conduction effects at doping levels above the Mott transition.
OM‐ and SEM investigations on the laser damage of tellurium dioxide single crystals
Authors: Malicskó L.
Published: January 2007

By means of optical (OM) and scanning electron microscopy (SEM) the morphological changes involved by intensive laser pulses in tellurium dioxide single crystals, were investigated. The typical morphological characteristics of the damaged crystal regions will be described and discussed.
A Study of precipitation morphology in NaCl:Sr and NaCl:Ba crystals
Authors: Reddy Katta Narasimha , Reddy A. Laxma
Published: January 2007

Single crystals of sodium chloride grown from melt containing different concentrations of strontium and barium have been observed to contain a second phase precipitating throughout the interior in the form of thin rods and well defined polygonal platelets. Two types of rods have been observed, one type oriented along 〈100〉 and the other along 〈110〉 directions. The platelets are variously in the form of hexagons, octagons, and rhombs. The precipitates disappear on quenching the crystal and reappear on aging the crystals under suitable conditions.
Resistance and inductance studies of Bi2−xPbxCa2Sr2Cu3Oy superconducting compounds
Authors: Muralidhar M. , Rao D. Mangapathi , Somaiah T. , Babu V. Hari
Published: January 2007

Bi2−xPbxCa2Sr2Cu3Oy compounds with (x = 0, 0.1, 0.2, 0.25, 0.3 and 0.4) were prepared by solid state reaction. The resistance and inductance results showed that transition temperature increases with increase in lead concentration. The highest value of Tc(0) observed is 109 K for Bi1.70Pb0.30Ca2Sr2 · Cu3Oy. The change of inductance per unit volume at liquid nitrogen temperature as a function of composition showed maximum change in x = 0.30 Pb‐doped sample. The results showed that the inductance change is maximum in samples which also showed highest Tc.
Filled SA phases in binary systems of terminal‐nonpolar compounds (IV). Mixtures of biswallow‐tailed compounds and nematogenic twin compounds
Authors: Pelzl G. , Humke A. , Demus D. , Weissflog W.
Published: January 2007

The phase diagrams of three binary systems of liquid crystals are presented whereby one component is a biswallow‐tailed compound and the second component is a member of homologous twin compounds. The most important feature of the diagrams is the occurrence of induced SA phases and reentrant nematic phases. The existence of the induced SA phase can be interpreted by the special molecular structure of the mixing components.
On chemical kinetics of silicon deposition from silane (II). Comparing 1st‐ and 0.5th‐reaction order
Authors: Kühne H.
Published: January 2007

Theoretical expressions for silicon layer deposition from silane pyrolysis within an open isothermal reactor tube has been derived for 0.5th order of chemical reaction with restricting the discussion to homogeneous gas reaction, and compared to the analogous expressions of chemical reaction characterized by 1st order relationship. Both kinds of theoretical equations give results free from contradictions when applied to experimentally based data of silane consumption on the one hand and silicon deposition distribution on the other, at least, with respect to those data published by Puga. First order reaction is characterized by an activation energy of ΔEaSi = 34 – 39 kcal/mole, and 0.5th order reaction by ΔEaSi = 23 – 26 kcal/mole. Chemical reaction of 0.5th order is to be preferred rather than 1st order.
Effect of the relative content of Y, Ba, and Cu on the superconducting transition characteristics of the YBaCuO System
Authors: Shpeizman V. V. , Orlova T. S. , Smirnov B. I. , Markov L. K. , Engert J. , Kaufmann H.‐J. , Rudolph K. , Matz W.
Published: January 2007

By varying the content ratio of the initial products, nine compounds of the YBaCuO system have been produced. These were studied to find their Tc values, critical currents jc at 77 K and effects of compression stress on the U(j)‐curves. Mechanical loading has been found to result in a shift of the U(j)‐curve towards a larger current. A correlation between the critical current value, the slope of the U(j)‐curve, and the stress induced shift is shown to exist. Samples with equal absolute deviations from the stoichiometric composition reveal close properties, the better the smaller is the deviation.
The coprecipitation of zinc aluminium hydroxides (refractory‐, absorbent‐, and catalyst precursors) from aqueous solution with ammonium hydroxide: Precipitate compositions and coprecipitation mechanisms
Authors: Doherty W. O. S. , Onuchejo E. M. T. , Packter A.
Published: January 2007

Zinc aluminium hydroxide hydrates were coprecipitated from different mixed cation solutions at Zn/Al2 ratios from 1/2 to 4/1. The coprecipitations were monitored by potentiometric titrations and the final coprecipitate compositions were examined by chemical analysis and atomic absorption spectrophotometry, X‐ray diffraction and preliminary thermal analysis. The product from Zn/Al2 = 1/2 solution was amorphous: at Zn/Al2 = 1/1.5, the main phase (after drying at 95 °C) was a zinc hydroxoaluminate Zn[Al(OH)4]2 together with some gibbsite: at Zn/Al2 = 1, the main phase was probably a solid solution (of Zn[Al(OH)4]2 with Zn2[Al2(OH)10]) together with Zn2[Al2(OH)10]: at Zn/Al2 = 2, the main phase was a mixture of Zn2[Al2(OH)10] with (ZnOH)4 [Al2(OH)10] and some gibbsite: at Zn/Al2 = 4, the main phase was (ZnOH)4 [Al2(OH)10] with some zinc hydroxide.
Studies on the lattice match and strain in the epitaxial growth of III – V alloys on inas and GaSb substrates
Authors: Gnanasundaram D. , Mani V. N. , Dhanasekaran R. , Ramasamy P.
Published: January 2007

The compositional conditions to deposit the epitaxial films of III – V materials lattice matched to InAs and GaSb substrates have been investigated and the results are presented in the form of charts. The validity of our theoretical predictions has been tested by comparing with the available experimental results. Strain in the GaxIn1 − xAsySb1 − y quaternary alloy has been visualised as three‐dimensional perspective plots.
2‐phenyl thiazolidine — its growth and characterisation
Authors: Umarani R. , Eswaramoorthy S. , Raju K. S.
Published: January 2007

The importance of 2‐phenyl thiazolidine lies in its being a model for penicillin, as the five‐membered thiazolidine ring happens to be the moiety of penicillin. This material is synthesised and crystallised (Tsukerman). The crystals are white in colour, transparent, needle‐shaped and of dimensions (0.2 × 0.3 × 0.4 mm3). Employing X‐ray diffraction studies, it is found that the crystal belongs to the orthorhombic system with the unit cell parameters a = 8.388(1), b = 18.114(2) and c = 5.625(1) Å. The space group is P 212121 and Z = 4. The absorption peaks pertaining to NH, NCS, methylene CH2 and aromatic C6H4 have been identified from the infrared absorption spectrum of the sample. The Proton Magnetic Resonance (PMR) spectrum fully accounts for the hydrogens in the sample thereby unambigiously supporting the proposed structure.
Formation of high resolution X‐ray diffraction pictures of crystal imperfections, their distortionless detection and unique interpretation
Authors: Bezirganyan P. H. , Aboyan A. O. , Khzardzhyan A. A.
Published: January 2007

A method of step‐by‐step scanning, free from all the deficiencies inherent in the known methods of projection topography is proposed. The proposed method allows one to detect high resolution, distortionless X‐ray diffraction pictures.
High‐frequency dielectric constant of AIIB2IIIC4VI ordered‐vacancy compounds
Authors: Neumann H. , Kissinger W. , Lévy F.
Published: January 2007

The mean high‐frequency dielectric constant of ZnIn2Se4, CdIn2Se4, ZnIn2Te4 and CdIn2 Te4 was determined from unpolarized infrared reflectivity spectra measured in the wavenumber range v̄ = 600 – 4000 cm−1. A simple relation based on the quantum dielectric theory for multibond crystals is proposed to estimate the mean high‐frequency dielectric constant of the AIIB2IIIC4VI compounds from individual bond susceptibilities. The results of the calculations are compared with existing experimental data, and susceptibilities of the HgCVI bonds are estimated.
KTiOPO4(KTP) crystal growth from high‐temperature solutions containing WO3
Authors: Shumov D. P. , Nikolov V. S. , Iliev K. N. , Aleksandrovskii A. L.
Published: January 2007

The process of seed growth of KTiOPO4 crystals from three different high‐temperature solutions containing WO3, with definite compositions is reported. The low viscosity and relatively slight change of the solubility of the KTP with the variation of the temperature allow the growth of adequately large crystals, free from inclusions, in the case of two tested techniques – slow cooling and temperature gradient. Conditions to avoid defects in the seed region have been found. The relatively high growth rates allow the production of crystals in a 5‐day growth run, that can be cut into samples oriented along synchronism for the second harmonic generation(SHG) with dimensions 8 × 8 × 7 mm3. SHG measurements reveal that the quality of the samples considered is comparable with KTP crystals grown from high‐temperature nonstoichiometric solutions.
Crystal and molecular structure of 6,13‐Di(ethoxycarbonyl)‐7,12‐dimethyl‐dibenzo [b.i.]‐1,4,8,11‐tetraaza[14]annulenato(2‐) nitrosocobaltat [C26H26O5N5Co] and the neutral ligand [C26H28O4N4]
Authors: Görls H. , Reck G. , Jäger E.‐G. , Müller K. , Seidel D.
Published: January 2007

Both title compounds crystallize in the orthorhombic space group Pnma with 4 formular units in the unit cell. The lattice parameters are: [C26H26O5N5Co], a = 8.589(4), b = 19.395(3), and c = 14.850(3) Å;[C26H28O4N4], a = 8.413(7), b = 19.166(4), and c = 14.807(28) Å. The crystal structures have been determined by direct methods and refined by full‐matrix least square calculations. The ligands have a pronounced saddle‐shaped conformation in each structure because of interactions of the methyl groups with the benzene rings. The overall conformations of the neutral ligand and the cobalt complex are remarkably similar.
On crystal growth of ammonium and potassium dichromate. A study of the shubnikov effect
Authors: Breidenstein B. , Follner H.
Published: January 2007

Growth and equilibrium forms of ammonium (A2/a) and potassium dichromate (P 1) have been calculated by means of the Fourier transform method of crystal morphology. Twin laws of potassium dichromate and heteroepitaxial intergrowth of both substances can be explained by partitions of space. According to Shubnikov the (001) planes of potassium dichromate crystals grown in aqueous solutions are always smooth, the parallel opposite planes, however, roughened. Wagner observed that this effect only occurs at temperatures shortly above or below 25 °C. The present investigation has shown that roughening of (001) appears at 25 °C after addition of potassium chromate to the potassium dichromate solutions. This means that the one‐sided intergrowth can be explained by a stereospecific adsorption of polychromates. Solution additions like potassium permanganate and Chromotrope 2B generate roughenings on both {001} faces. X‐Ray diffraction investigations can be interpreted in such a way that the intergrown plates are mirror symmetric oriented to two planes being normal to the a‐ and b‐axes. This is in accordance with repeated formation of intergrown plates.
Thermodynamic analysis and technology of preparation of high‐Tc superconducting system YBa2Cu3O7−x
Authors: Huan Le Van , Tuong Vu Huu , Tuong Le Thi Cat
Published: January 2007

By modeling the equilibrium state of the phase formation reaction of High‐Tc superconducting phase 1:2:3 (YBa2Cu3O7−x) and using the results of P‐T−x correlation investigation of some authors, the variation of Gibbs free energy (ΔGm) versus temperature has been calculated. On the basis of the variation of ΔGm, the technology procedure of preparation of phase 1:2:3 with desired x has been established to meet requirement of basic investigation and application of High‐Tc superconductors YBa2Cu3O7−x.