bluuebunny/crossref_metadata_2025_split huggingface dataset:
The crystal and molecular structure of hydrazine‐N, N′‐dicarbonic‐acid‐di‐(4‐chlorophenyl)‐ester Dihydrate, C14H10Cl2N2O4 · 2 H2O
Authors: Reck G. , Just M. , Koch R. 
Published: January 2007

AbstractThe crystal and molecular structure of the title compound has been determined by X‐ray diffraction techniques. It crystallizes in the monoclinic space group C2/c with cell parameters a = 30.719(8), b = 5.016(3), c = 10.946(8) Å, and β = 106.08(3)°. The structure was solved by direct methods and refined to R = 0.038. The drug molecule consists of two chemically identical parts, symmetry related by a two‐fold axis coinciding with that of the space group. Hydrogen bonds connect water and drug molecules forming infinite layers parallel to the y, z‐plane.
The precipitation of alkaline‐earth metal‐nickel, aluminium (chromium (III) and iron (III)), silicyl(titanyl and zirconyl) hydroxide, carbonate and oxalate precipitate precursors for alkaline‐earth metal oxyanion salt ceramics and allied materials – a review of small scale laboratory studies and industrial patents
Authors: Packter A. 
Published: January 2007

AbstractThe alkaline‐earth metal – nickel, aluminium, chromium III, iron III, silicyl, titanyl and zirconyl hydroxide, carbonate and oxalate coprecipitates are the precursors for the preparation of the corresponding alkaline‐earth metal oxyanion salt refractories, magnetics, dielectric and optical ceramics, cements and allied materials. The small‐scale laboratory studies on the coprecipitations of these precursor materials, their compositions and the coprecipitation mechanisms are reviewed and the relevant industrial patents are described (140 references).
Formation of inclusions in CaF2 single crystals
Authors: Dressler L. , Reimann R. 
Published: January 2007

AbstractIt is reported on formation of inclusions during the Stockbarger growth of CaF2. It the centre of this paper, hollows (gaseous or vacuum inclusions) are considered. Two different kinds of formation processes being possible under special growth conditions are discussed (segregation of gaseous impurity, entrapment of impurity‐rich liquid at cell boundaries of growth cells).
The current understanding of epitaxial CVD silicon doping in the light of modelling and theory development (I) empirical foundations and process controlling equations
Authors: Kühne H. 
Published: January 2007

AbstractThe paper sequently published in five parts deals with the logical interdependence between the technological process of silicon layer doping and the situation of its being empirically governed on the one hand, and its being theoretically explained on the other. The present first part of the paper concerns a brief description of epitaxial CVD silicon layer deposition and layer doping, the main controlling parameters of the latter, and how doping is governed by these parameters. The empirical basis knowledge linking the measuring control values of the process to specific layer properties in the form of control graphs, are transformed to more general empirical control equations of layer doping. Finally, representing the doping process analogous to cybernetic systems, an empirically based and nearly complete model equation is presented.
Twin laws explained by partitions of space
Authors: Follner H. 
Published: January 2007

AbstractTwin laws of monoclinic potassium feldspars, potassium sulphate, cerussite and hexabromobenzene can be explained by partitions of space. The face indices of the crystals denote points of a lattice in the reciprocal space. A Fourier transform leads to the morphological lattice. The reciprocal crystal is the Dirichlet domain of the morphological lattice and the structural content consisting of groups of atoms or molecules is the morphological unit. The bond strength between neighbouring morphological units is proportional to the area of the common face of the reciprocal crystals. The reciprocal crystal represents the energetical structure of a crystal. Twins can be explained by continuation of the energetical structures across the twin boundaries. The symmetry operations result from pseudosymmetries of the reciprocal crystals. It is possible to predict planes favoured for the formation of twins or parallel grown individuals.
Heat capacity and lattice anharmonicity in CdBIVC chalcopyrite compounds
Authors: Möller W. , Kühn G. , Neumann H. 
Published: January 2007

AbstractThe heat capacity at constant pressure of CdSiP2, CdGeP2, CdSnP2 and CdGeAs2 is measured in the temperature range from 300 to 500 K. The anharmonic contribution to the heat capacity is evaluated and it is shown that the degree of lattice anharmonicity decreases with increasing atomic weight of the constituent atoms of the compounds. Comparing the temperature variation of the heat capacity and of the thermal expansion coefficient some conclusions are made regarding the interatomic potential in the AIIBIVC compounds.
Thermal expansion anisotropy and individual bond expansion coefficients in ternary chalcopyrite compounds
Authors: Neumann H. 
Published: January 2007

AbstractThe individual bond expansion coefficients of the AIIBIVC and AIBIIIC2VI chalcopyrite compounds are calculated from the principal linear thermal expansion coefficients of the lattice parameters using the regular BC tetrahedron model and a model with a temperature independent free parameter of the lattice. It is shown that the bond expansion coefficients derived from the latter model are in better agreement with the trends found for the interatomic forces in the chalcopyrite compounds and observed for the thermal expansion coefficients in the binary AC, AIIC and BC compounds.
Dielectric studies of lead nitrate phosphate single crystals
Authors: Desai C. C. , Ramana M. S. V. 
Published: January 2007

AbstractFerroelectric Lead Nitrogen Phosphate (LNP) single crystals have been synthesized using the controlled reaction between lead nitrate and orthophosphoric acid solutions by slow diffusion process in silicagel medium. The colourless transparent LNP crystals upto 6 × 4 × 3 mm3 in size have been grown at room temperature. The dielectric measurements have been carried out in the temperature range between 300 to 690 K. The effect of applied frequency on the dielectric constants and dielectric losses has been investigated. It has been observed that the mechanism of the dielectric behaviour is different in the lower and higher frequency and temperature ranges. The activation energy of the oscillators has been calculated and found to be 1.125 eV. Attempt has been made to draw some qualitative conclusions, taking in view, the existing theories of various kinds of polarizations and implications.
Natural convection during directional solidification of an AlZn eutectic
Authors: Tuček V. , Holeček S. , Kubíček L. 
Published: January 2007

AbstractA study was made of the buoyancy convection of melt provoked by temperature gradient of an orientation identical to that of the gravity vector. The convection was assessed on the basis of temperature fluctuations in the melt. The critical Rayleigh numbers for periodic and turbulent flow were determined. Both periodic and turbulent flow gives rise to transverse “bands” in the structure of the eutection obtained by directional solidification. The intensity of unstable flow affects the number of eutectic crystallites in the sample.
Structure determination of polytypes (II)
Authors: Sedlacek P. , Kuban R.‐J. , Backhaus K.‐O. 
Published: January 2007

AbstractIn this part different methods for structure determination of polytypes with diffraction methods are described. These methods are applied to periodic polytypes consisting of one or more sorts of layers and to disordered polytypes consisting of one sort of layers. Furthermore an example for the determination of the structural principle is given.
X‐ray investigation of the mechanism of phase transformation in single crystals of ZnS, ZnxCd1−xS and ZnxMn1−xS (I). Calculation of diffraction effects by a three parameter model
Authors: Sebastian M. T. , Krishna P. 
Published: January 2007

AbstractHexagonal close‐packed (2H) single crystals of ZnS, ZnxCd1−xS and ZnxMn1−xS are known to undergo solid state transformation to the cubic close‐packed (3C) and 6H‐structures on annealing at elevated temperatures. The transformations occur by the non‐random nucleation of stacking faults on individual close‐packed layers parallel to (0001). The nature of the faults involved and their probability distribution during transformation determine the diffraction effects produced along the 10. L reciprocal lattice row by a crystal quenched in an intermediate state of transformation. We have investigated the mechanism of the transformation by comparing the diffraction effects recorded from such crystals on a single crystal diffractometer, with those calculated for an assumed model of the transformation.It is known that in these materials the faults involved in the transformation are deformation faults. To explain the observed diffraction effects we develop a three parameter theoretical model employing a fult probability α for the radom insertion of a deformation fault in the 2H structure, a fault probability β for the deformation faults to occur at three layer separations and a fault probability γ of their occcurrence at 2‐layer separations. The probability α corresponds to the development of a fresh nucleus, the probability β to the growth of the 6H nucleus and the probability γ to the growth of a 3C nucleus. This paper develops the necessary theory of X‐ray scattering for such a model of the transformation and predicts the diffraction effects for different values of α, β, and γ. The next paper compares these results with experimental observations.
Simulation of contrasts in X‐ray plane wave topographs of quartz crystals with induced growth striations
Authors: Härtwig J. , Jäckel K.‐H. , Lerche V. 
Published: January 2007

AbstractUsing system theoretical methods and fast discrete Fourier transforms, contrasts in plane wave topographs of crystals with impurity distributions of any form can be simulated with high accuracy and in a short time.
The current understanding of epitaxial CVD silicon layer doping in the light of modelling and theory development (V). Special features of doping with arsenic in the range of small layer growth rates
Authors: Kühne H. , Morgenstern Th. 
Published: January 2007

AbstractIn the SiH4‐HCl‐AsH3‐H2 system of depositing epitaxial silicon doped with arsenic an equilibrium‐like doping process has been obtained by way of experiments not only as a limiting case at high deposition temperatures, as had been shown formerly, but also in the range of lower temperatures when the layer growth rate falls below a critical value. By means of introducing the term of a critical rate the theory of dopant incorporation, published in the Parts I–IV of the present report, has been extended to full completeness.
Incorporation of nitrogen into galliumarsenide grown by chloride VPE
Authors: Schwetlick S. , Seifert W. , Butter E. , Hörig W. , Pickenhain R. , Schwabe R. 
Published: January 2007

AbstractThe incorporation of nitrogen into GaAs in the halide‐VPE system using NH3 as the doping source is investigated. The concentration of incorporated N depends on the NH3 flow rate and increases with decreasing deposition temperature. Concentrations up to 6 × 1017 cm−3 could be detected far above the calculated equilibrium value.By a comparison of SIMS‐data with those obtained from IR it is found that most of the N‐atoms are situated substitutionally on As lattice sites.Normal‐pressure 2 K photoluminescence measurements show N‐related luminescence peaks at 1.508 and 1.496 eV. Most probably this luminescence arises from complexes of N with undeliberately introduced impurities. For the 1.508 eV center a complex SiGa‐NAs is discussed. — A new N‐related metastable deep center with the energy levels Ec‐0.33, Ec‐0.41, and Ec‐0.68 eV could be found by DLTS.
X‐ray determination of the polarity of zincblende‐structure crystals
Authors: Berger H. 
Published: January 2007

AbstractAn X‐ray diffraction procedure for the determination of the polarity of noncentrosymmetric crystals by measuring the integrated reflections of opposite polarity on one surface of the crystal is described. The observed intensities must be corrected for the different asymmetries of the two reflections. To estimate the influence of crystal perfection on the correction factor, the ratios of the integrated reflections were calculated numerically for dynamic diffraction. The method has been applied for determining the polarity of CdTe.
Crystal growth in an improved bridgman variable shape graphite furnace
Authors: Nicoarǎ Irina , Nicoarǎ D. , Aczel Otto 
Published: January 2007

AbstractAn improved Bridgman‐type crystal growth system is presented. By using a new type of heaters, fluoride single crystals with a diameter up to 50 mm and 150 mm length have been obtained. The dislocation density distribution has been examined in different growth conditions.
Photoconductivity of (ZnS, CdSe): Dy
Authors: Bhushan S. , Giriya L. C. 
Published: January 2007

AbstractPhotoconductivity rise and decay curves have been investigated for (ZnS, CdSe): Dy as a function of flux concentration, concentration of Dy, applied voltage, atmosphere during preparation and different excitation intensities. Substitution of Dy increases the photocurrent by five times. Maximum photocurrent is also observed at a particular concentration of flux. The decay is of hyperbolic nature and the trap depths are found at depths 0.49 eV and 0.54 eV which depend upon the concentration of Dy.
Influence of mixing on batch precipitation
Authors: Söhnel O. , Mullin J. W. 
Published: January 2007

AbstractThe influence of mixing on the induction period of batch precipitation of Ag2WO4, CaWO4 and SrWO4, in the supersaturation ranges 3.7–7.8, 32–134 and 121–210 respectively, has been studied at 25 °C. Increasing the intensity of mixing invariably decreases the induction period in all three systems. This effect in absolute terms is more pronounced at the lower supersaturations than at the higher.
Polymorphous transformation of quartz induced by mechanical treatment
Authors: Steinike U. , Uecker D.‐Chr. , Sigrist K. , Plötner W. , Köhler Th. 
Published: January 2007

AbstractBecause of its strongly damaged structure (partially crystalline) mechanically activated α‐quartz is not transformed to β‐quartz. Rather, mechanically activated α‐quartz is rapidly transformed to the cristobalite modification even at temperatures as low as 1200 °C. The acceleration and temperature shift of the quartz‐cristobalite transformation is caused by mechanically induced defects. The activation energy of the transformation is thus reduced by about 50%.
Gross dissolution of natural rhombohedral calcite crystal in nitric acid
Authors: Mehta B. J. , Sidpara G. R. 
Published: January 2007

AbstractGross dissolution of natural calcite crystal in concentrated nitric acid give interesting results. The gross dissolution is maximum at 6 M concentration of HNO3. The activation energy increases as the concentration of HNO3 increases. Similarly pre‐exponential factor is also increases as concentration increases. The combined effect of activation energy and pre‐exponentail factor gives the peak at 6 M concentration of nitric acid.
On the surface mechanism of crystal melting
Authors: Vlasov A. D. 
Published: January 2007

AbstractA crystal melting mechanism is proposed. The melting is caused by enhanced thermal expansion of the lattice on the surface and around structure defects. For the microcrystallites formed this way an approximate calculation of parameters is made. The microcrystallites surface area per mole is shown to be thousands of m2, the radius within 1.5 to 10 nm, the gaps between microcrystallites — by 30 percent more than the lattice interatomic distance. The mean thermal linear expansion coefficients determined on the crystal surface are roughly ten times as much as the bulk values.
Helical structure and threshold voltage of cholesteric‐nematic phase change at different anchoring conditions
Authors: Hauck G. , Koswig H. D. 
Published: January 2007

AbstractThe helical structure of cholesteric mixed systems and their electro‐optical behaviour are studied at planar and pretilted surface orientation. The results indicate that the influence of the forces of wall orientation is decreased by the helical structure. To prove this model strong and weak anchoring conditions of the molecules in the cholesteric mixture at the substrate surface are realized. Also the behaviour of the electro‐optical threshold voltage at different surface conditions supports the assumptions concerning the helical structure.
Surface morphology and quality of potassium bichromate crystals obtained from aqueous solutions in relation to growth conditions
Authors: Szurgot M. , Sangwal K. 
Published: January 2007

AbstractThe characteristics of macrospiral layers on growth surfaces of potassium bichromate crystals and their quality are examined in relation to growth conditions. It was observed that the layers become thick and rounded, more inclusions are trapped and the crystal quality deteriorates with an increase in supersaturation, while an opposite effect is noted with an increase in growth temperature. The observations are discussed from the standpoint of crystal growth theories.
Specific heats of FCC solid solutions of the Bi2O3‐Y2O3 system
Authors: Berezovskaya Yu. , Budurov S. , Spasov T. 
Published: January 2007

AbstractFor the first time specific heats of the face centered cubic solid solutions (Bi2O3)1−x(Y2O3)x in the temperature range 350–1000 K were measured by means of Differential Scanning Calorimetry. Samples were also investigated with thermal expansion. The results showed the phase transitions for (Bi2O3)0.75 (Y2O3)0.25, which is acsribed to δ → δ* change in lattice mentioned in literature and for (Bi2O3)0.58(Y2O3)0.42, which is connected with a metastable behaviour of this sample.
Precision measurement of lattice parameters in LiF monocrystals
Authors: Dressler L. , Griebner U. , Kittner R. 
Published: January 2007

AbstractThe methodic possibilities of measurements by the Bond‐method for a highly precise determination of the lattice parameters in block structures with small block desorientation angles in the region of angular seconds or angular minutes (LiF crystals) have been examined. The lattice distorsion in two planes perpendicular to the (001) surface of crystalis described. The same planes have also been examined by elastooptic methods. In both planes we got for the lattice parameters: a1 & a2 > a3 (a1 and a2 parallel to the surface of crystal, a3 perpendicular to the surface of crystal); i.e. we could observe a dilatation of the unit cell parallel to the surface of the crystal. Special results concerning the distribution of local lattice parameters along the surface of sample are discussed in connection with the results of elastooptic observations.
Growth of crystals of calcium sulphate in silica gel in presence of additive and their characterisation
Authors: Kumareson P. , Devanarayanan S. 
Published: January 2007

AbstractProcedure for the growth of calcium sulphate dihydrate crystals in silica gel, in the presence of barium chloride as additive, is described. Optimum conditions for the growth of good quality crystals are worked out. The crystals are characterised by laser Raman spectroscopy, infrared spectroscopy, thermogravimetric analysis and Atomic absorption spectroscopy. It is shown that crystals in the presence of the additive have a greater degree of perfection than those without additive. Amount of water in the crystals is estimated as 20.97%. Presence of calcium and absence of barium in the crystals are indicated.
Depth profile of the microhardness in helium implanted GaP
Authors: Ascheron C. , Neumann H. 
Published: January 2007

AbstractDepth profiles of the damage density and the microhardness are measured in GaP single crystals implanted with 1 MeV helium ions. From an analysis of the experimental data it follows that the microhardness increases up to a damage density of about 16% due to point defect hardening. At higher damage densities the microhardness decreases rapidly, probably due to the formation of extended defects.
Slip band formation during bending of gap wafers
Authors: Jurkschat K. , Wagner G. , Paufler P. 
Published: January 2007

Abstract{001} LEC‐GaP:S wafers were deformed between 470 °C and 640 °C. {111} slip planes of maximum resolved shear stress were activated. Heights and densities of slip steps have been measured by optical and electron microscopy. At lower temperatures deformation proceeds mainly by growth of step heights whereas at higher temperatures bending is accomplished by the increase of slip band density rather than of height.
Revealing of lattice defects on (111) faces of gallium phosphide and indium phosphide by chemical etching
Authors: Wagner G. , Gottschalch V. 
Published: January 2007

AbstractA solution is presented suitable for revealing lattice defects on (111) phosphorous faces of GaP and InP. It is possible to distinguish between pits originated by grown‐in dislocations and microdefects such as perfect loops, faulted loops and precipitates and/or inclusions. Moreover it is also possible to reveal large stacking faults of Shockley type and microtwin lamellae. One to one correlations have been given by means of transmission electron microscopy.
Lattice constants and site preference in the system Ni2SiO4—Co2SiO4
Authors: Zahn A. , Schreiter P. 
Published: January 2007

AbstractMost important supposition for a possible site preference in a olivine solid‐solutions are besides the different crystal chemical properties of M cations (size, electronegativity, crystal field stabilization energy) the differences between the both octahedral coordinated sites M1 and M2 of the olivine structure. Using this regularities the site preference in the system NiCo olivines is predicted. If site preferences are existing, it is possible to deduce deviations of the Vegard's rule in the system Ni2SiO4—Co2SiO4 using geometrically‐structurally considerations. The plot of experimentally determined lattice parameters in this solid solutions system shows the existing of the proposed deviations of the Vegard's rule and evidences the site preferences of Ni2+ in the M1‐ and Co2+ in the M2 octahedra only by determination of lattice parameters.
Calculation of one‐dimensional temperatures profiles in a crystal growth furnace with special respect to germanium
Authors: Buhrig E. , Hein K. , Walter G. , Geidel B. 
Published: January 2007

AbstractIn the paper a one‐dimensional method of calculation for temperature profiles in crystal growth furnaces is described. It is characterized by high flexibility. The model applied to our own calculations is based on heat balances in segments of a multi‐zone furnace and presupposes the availability of experimental data which allow the coefficients to be derived which are necessary to carry out the calculations. — The results of numerical calculations demonstrate the applicability of an existing furnace unit to directional crystallization of germanium.
Liquid crystalline swallow‐tailed compounds (II) dielectric relaxation
Authors: Kresse H. , Rabenstein P. , Stettin H. , Diele S. , Demus D. , Weissflog W. 
Published: January 2007

AbstractDielectric investigations in the kHz‐range on swallow‐tailed liquid crystals show a strong decrease of the dielectric constant as well as of the dielectric loss parallel to the nematic director with decreasing temperature. In the perpendicular direction no strong anomaly has been observed. By consideration of X‐ray data of the SA phase the dielectric results can be interpreted by the dipole‐dipole interaction which is forced by the anisotropy of repulsive forces of the respective molecules.