bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microhardness‐Plasmon Energy‐Bulk Modulus Relationship in Ternary Chalcopyrite Semiconductors
Authors: Kumar V. , Prasad G. M. , Chandra D. 
Published: January 2007

AbstractIn this paper simple relations have been proposed for the calculation of microhardness and bulk modulus of I–III–VI2, and II–IV–V2, chalcopyrite semiconductors. The present calculations do not require any experimental data except the plasmon energy of the semiconductors. A linear relation between bulk modulus and microhardness has also been obtained. Our calculated values are in fair agreement with the experimental values and the values reported by different workers.
Optical Absorption Edge of Mg + Zn: LiNbO3
Authors: Yang Xiaolong , Xu Guanfeng , Li Heping , Zhu Jianguo , Wang Xiu 
Published: January 2007

AbstractThe optical transmittance of LiNbO3 single crystal double doped with MgO and ZnO was measured from the ultraviolet to the visible range. The wavelength dependence of the absorption coefficient α and its root α1/2 (α versus hv and α1/2 versus hv, respectively) were calculated and the characteristics of the absorption edge were discussed. The energy gaps Eg and Eg of the crystals which correspond to the direct transition and the indirect transition, respectively, and the energy of phonons taking part in the indirect transition were calculated. The effects of dopants Mg and Zn on the optical absorption properties are discussed. It was found that the energy Eg of our sample which was double doped with MgO and ZnO was smaller than that of congruent LN, causing the indirect transition absorption edge to move towards the infrared.
A Comparison of Different Multiple‐Crystal Diffractometer Arrangements to Measure the Reflection Curve of SiGe Layers on Si Substrates
Authors: Zaumseil P. 
Published: January 2007

AbstractFive different double‐ and triple‐crystal diffractometer (DCD, TCD) arrangements are used to measure the reflection curve of a heteroepitaxial structure consisting of a 41 nm thick Si1‐xGex layer (x = 0.327) on an Si‐100 substrate. The advantages and disadvantages of these arrangements including different monochromator/collimator and analyzer set‐ups are discussed. It is shown that even for this perfect heteroepitaxial layer TCD measurements provide the best results especially in the reproduction of deep minima of the intensity oscillations in the reflection curve.
Effect of Ampoule Rotation on Growth of InGaAs Ternary Bulk Crystals from Solution
Authors: Hayakawa Yasuhiro , Ando Masahiko , Koyama Tadanobu , Kumagawa Masashi , Ozawa Tetsuo , Masaki Miyuki , Takahashi Katsumi 
Published: January 2007

AbstractInxGa1‐xAs (x = 0.045) ternary bulk crystals were grown on GaAs seeds from an In–Ga–As solution by the temperature‐difference method modified to rotate a growth ampoule. The effect of ampoule rotation on the profiles of the composition and the growth rate were investigated. The In compositional profiles were uniform irrespective of the ampoule rotation. On the other hand, the growth rate at the center of the crystal increased from 40 μm/h at 0 rpm to 55 μm/h at 100 rpm. The profile of growth rate changed from concave to convex toward the seed due to the ampoule rotation. Flow patterns and compositional profiles in the solution were simulated by solving four equations: Navier‐Stokes, continuity, energy, and solute diffusion. The ampoule rotation enhanced the transportation of As component from the GaAs feed toward the seed at the central region in the solution. This led to the increase of the growth rate.
Growth and Optical Absorption of Photorefractive Bi12SiO20 Crystals Doped with Zn and Cd and Co‐doped with P
Authors: Petrova Dimitrina , Gospodinov Marin , Sveshtarov Peter 
Published: January 2007

AbstractSingle crystals of Bi12SiO20 (BSO) Zn‐ and Cd‐doped and co‐doped with P have been grown by Czochralski technique and optimum conditions for producing optically homogeneous crystals were established. The transmission and reflection spectra have been measured in the range 0.38–0.85 μm and absorption coefficients have been determined. The Zn dopants have been found to bleach the crystals and decrease the transmission shoulder, whereas Cd dopant increases the absorption and makes the shoulder well pronounced. P‐doping strongly decreases the transmission shoulder and shifts absorption to shorter wavelengths. The absorption Coefficient of BSO doped with P has been found to decrease with dopant concentration increase up to 3 mol% P and above it increases with P concentration in the whole studied range. Zn + P‐ and Cd + P‐co‐doping (P concentration in the crystal less than 3 mol%) decreases strongly the absorption coefficient and shifts the spectra to short wavelengths.
A Novel Structure of Bipyridine Coordinated with Copper (II): [Cu(bipy) (H2O)3] · (NO3)2
Authors: Jianmin Li , Jianbin Zhang , Yanxiong Ke , Xintao Wu 
Published: January 2007

AbstractThe crystal structure of the mononuclear copper (II) complex containing a 2,2′‐bipyridine and three water molecules, [Cu(bipy) (H2O)3]. (NO3)2, is reported. The copper coordination polyhedron is a five‐coordinated distorted pyramid.
2′‐Methyl‐3′‐nitroflavone
Authors: Kendi E. , Özbey S. , Tunçbilek M. , Ertan R. 
Published: January 2007

AbstractThe crystal and molecular structure of the title compound has been determined by direct methods and refined to a final R of 0.044. The compound crystallizes in space group P21/n with cell dimensions a = 16.681(2), b = 3.838(1), c = 20.550(4) Å, and β = 104.21(2)°. The phenyl and benzene rings of the title molecule are quite planar. The γ‐pyrone ring exhibits maximum deviation 0.032(4) Å from planarity and makes a dihedral angle of 139.8(2)° with the 2‐phenyl substituent.
The Crystal and Molecular Structure of Two Drug Compounds: Tazettine and Corydaldine
Authors: Ide S. , Şener B. , Temizer H. , Könükol S. 
Published: January 2007

AbstractThe title compounds Tazettine (C18H21NO5) and Corydaldine (3,4‐dihydro‐6,7‐dimethoxy‐1(2H)‐isoquinolinone, C11H13NO3) have been isolated from the bulbs of Pancratium maritimum L. (Amaryllidaceae) and Corydalis solida subspecies brachyloba, respectively. The X‐ray structures were solvcd for Tazettine (I) and Corydaldine (II) (λ MoKα, R = 0.0499 and 0.0418, respectively). Crystals of (I) are orthorhombic, a = 7.115(1), b =13.377(1), c = 16.878(1) Å, Z = 4, Dcale = 1.370 g. cm−3, space group P212121. Crystals of (II) are monoclinic, a =10.641(1), b = 6.636(1), c = 14.938(1) Å, β = 90.31(1)°, Z = 4, Dcalc = 1.305 g. cm−3, space group P21/a.
Thermal Analysis of LiGaO2 and NaGaO2
Authors: Weise S. , Neumann H. 
Published: January 2007

AbstractThe high‐temperature thermal properties of the ternary oxides LiGaO2 and NaGaO2 are studied by simultaneous differential thermal analysis and thermogravimetry between room temperature and about 1700 °C. For the melting temperature of LiGaO2 a value of 1595 ± 10 °C is determined. NaGaO2 undergoes a solid state phase transition at 1280 ± 10 °C and melts at 1395 ± 10 °C.
Growth of Smectic B (Crystal) and Phase Transitions in Liquid‐Crystalline PBnA (n = 4, 5, and 6) Compounds
Authors: Potukuchi D. M. , Lakshminarayana S. , Prabhu C. R. , Pisipati V. G. K. M. 
Published: January 2007

AbstractThermal microscopy, calorimetric (DSC) and dilatometric investigations are reported in three liquid‐crystalline compounds of n(4‐n‐phenylylbenzylidene) 4‐n‐alkylaniline series viz., PBnA for n = 4, 5, and 6. They exhibit nematic, smectic B (cryst) and smectic E (monotropic) polymorphism. Effective role of terminal phenyl end chain is discusscd for the occurrence of 3D‐ordered smectic B and smectic E phases. Density jumps and associated volume expansion coefficient anomaly infer first order nature of isotropic to nematic (IN) and nematic to smectic B (NB) transitions. Exponental growth of three‐dimensional hexagonal positional correlations estimated in the vicinity of nematic to smectic B transition through the β exponent infers the Van der Waals type of molecular interactions. Pressure dependence of transition temperatures are estimated, IN and NB transitions and thermal stablity are discussed.
Control of the Growth Optimum in Producing High‐Quality CaF2Crystals by an Improved Bridgman‐Stockbarger Technique
Authors: Mouchovski J. T. , Penev V. Tz. , Kuneva R. B. 
Published: January 2007

AbstractThe axial temperature distribution in an empty crucible and the determination of quenched interface within fixed crucible were investigated to find the relationships governing the growing process of CaF2by Bridgman‐Stockbarger methods. A system of additional molybdenum reflective sheaths was placed into the furnace unit and its effect on the temperature field was estimated in order to achieve the growth optimum. A long liner into the diaphragm bore of the furnace and a number of thin rings slipped on the crucible stem were found capable to provide a reproducible optimum on each stage of growing in single and multicamera crucibles at a relatively low level of power supply. Single and in‐group growth experiments were carried out using high density quenched ingots purified from oxygen contaminants through high temperature treatment of fluorspar. The properties of the grown crystals were found to depend on the degree of the fluorspar purification and on the improvement of the thermal conditions yielding either competitor or laser‐grade CaF2. In multicamera crucibles the crystals grown in the central compartment are of better characteristics than those in the peripheral ones.
X‐ray Topographic Assessment of Defects in Pure and Substituted Hexaferrite Crystals
Authors: Raina Urvashi , Bhat Sushma , Kotru P. N. , Franzosi P. , Licci F. 
Published: January 2007

AbstractResults of X‐ray diffraction topography, in reflection and transmission scanning geometry, of flux grown single crystals of substituted and unsubstituted hexaferrites bearing composition SrGaxInyFe12‐(x+y)O19 (where x = 0, 5, 7, 9; y = 0, 0.8, 1.3, 1.0) are presented. Diffraction topographs reveal defects like misoriented grains, dislocations, cavities, inclusions, and the strain patterns in these crystals. The unsubstituted hexaferrites exhibit better perfection when compared to the substituted ones. The study is reported to support the results obtained by chemical etching and fractography, besides yielding additional information covering defects.
Enhanced Automatic Diameter Control System of Czochralski‐grown Crystals
Authors: Kochurikhin V. V. , Shimamura K. , Fukuda T. 
Published: January 2007

AbstractThe automatic diameter control system with two ways of the crystal diameter determination is described. The correction of temperature oscillations during the growth process is applied in the describing system. Also, it allows to estimate the crystal quality already during the growth process. The control system is intended for the growth of crystals with different physical properties.
Transport Coefficients of (Bi1‐xSbx)2Se3 Single Crystals
Authors: Drašar Č. , Klichová I. , Koudelka L. , Lošťák P. 
Published: January 2007

Abstract(Bi1‐xSbx)2Se3(x = 0.0 to 0.2) single crystals were prepared using a modified Bridgman method. Measurements of the Hall coefficient RH, electrical conductivity σ and Seebeck coefficient α showed that incorporation of the antimony atoms into the Bi2Se3 crystal lattice results in an increase in the free electron concentration for a low antimony content, whereas the free electron concentration is suppressed in the range of a high antimony content. This effect is explained qualitatively by changes in the concentrations of point defects in the (Bi1‐xSbx)2Se3 crystals. We asume that the substitution of Bi atoms by Sb atoms results in a decrease in the concentration of Se vacancies V and antisite defects BíSe. The course of the dependences of In (RHσ) vs In T manifests that in the temperature region of 100–400 K transport properties of the studied crystals are characterized by a mixed transport mechanism of free carriers, mainly on acoustical phonons and ionized impurities.
Hardness Studies and Fracture Behaviour on Flux‐grown YFeO3 Single Crystals
Authors: Bamzai Krishen , Kotru P. N. , Wanklyn B. M. 
Published: January 2007

AbstractResults of Vickers' microhardness (Hv), fracture toughness (Kc), brittleness index (Bi) of (110) and (001) faces of flux‐grown yttrium orthoferrite crystals, in the load range of 10–100 g, are given. The cracks are classified into Palmqvist and median types. The transition from Palmqvist to median type of cracks is shown to take place when the applied load exceeds 50 g. Application of the formula of NIHARA et al. for only median cracks leads to calculation of more precise values for fracture toughness and brittleness index than what was reported earlier (BAMZAI et al.) as an average value.
Oxidation Kinetics of Amorphous, Polycrystalline, and Nanocrystalline Co33Zr67 Alloys
Authors: Spassov Tony , Tzolova Genka 
Published: January 2007

AbstractThe oxidation kinetics of amorphous, polycrystalline, and nanocrystalline CoZr2 alloys have been studied under isothermal conditions in air atmosphere with a microbalance. DSC and X‐ray diffraction were used to study the influence of oxidation on crystallization. The three alloys under investigation which have the same composition but differ in the microstructure showed noticeable differences in their oxidation behaviour: the oxidation of the amorphous alloy is characterized by a very fast initial oxygen absorption step, completed in less than 1–2 min, followed by a slow oxide growth obeying a logarithmic time law at 400 °C. The polycrystalline thermodynamically stable tetragonal alloy absorbs small amounts of oxygen and obeys a parabolic rate law in the temperature range 500–800 °C. The activation energy of oxygen diffusion in tetragonal CoZr2 was determined from the temperature dependence of the parabolic rate constant. The intermediate nano‐crystalline phase with a local structure more closely packed and ordered than that of the precursor amorphous phase, shows an oxidation behaviour similar to that of the tetragonal phase, but with a different time exponent.
Low‐temperature Magnetic Properties of Terbium Orthoferrite Single Crystals
Authors: Guretskii S. A. , Ges A. P. , Luginets A. M. , Milovanov A. S. , Fil' V. D. , Zherlitsyn S. V. 
Published: January 2007

AbstractSpontaneous and by an external magnetic field induced magnetic phase transitions in TbFeO3 have been experimentally studied. Precision investigations of velocities of transmission and attenuation of sound wave were made, the processes of formation and rearrangement of magnetic structure examined and its change under the influence of external magnetic field explored. This has been made possible by the development of methods of controlled growth of rare‐earth orthoferrites resulting in the formation of high‐quality single crystals of required size with reproducible physical properties. The measurements were taken in the temperature range from 0.45 to 8.0 K. From the threshold Geld values a Ha  T phase diagram for TbFeO3 has been plotted.
Transport Properties of TlInSe2 Single Crystals
Authors: Elshaikh H. A. 
Published: January 2007

AbstractSingle crystals of TlInSe2 were prepared by a special modified Bridgman technique. The influence of temperature on the electrical conductivity, Hall effect, Hall mobility, and the carrier concentration was investigated in the temperature range 190–625 K. The energy gap of conduction was calculated. The scattering mechanism of the charge carrier was discussed in the same temperature range. Beside this, the thermoelectric power was measured in a temperature range extending from 190 up to 485 K.
On the Determination of Birefringence of Liquid Crystals by the Interference Method
Authors: Moldovan R. , Tintaru M. , Frunza S. , Beica T. , Polosan S. 
Published: January 2007

AbstractA new method of processing the experimental data in the interference method for the determination of birefringence of liquid crystals which allows obtaining results in good agreement with those from prism or wedge methods, is presented.
The Influence of the Shape and the Incompatibility of Molecular Moieties on the Structure of Smectic Mesophases
Authors: Pelzl G. , Diele S. , Lose D. , Ostrovski B. I. , Weissflog W. 
Published: January 2007

AbstractFor selected compounds with perfluorinated chains the structure of smectic phases was investigated by X‐ray diffraction measurements. For rod‐like compounds with only one terminal perfluorinated chain the incompatibility of the hydrocarbon and the fluorocarbon moieties leads to a segregation of both parts which can be considered as microphase separation.For swallow‐tailed compounds the structure of smectic phases depends on the position and the length of the perfluorinated chains. If the steric interaction dominates an antiparallel packing of the molecules within the smectic layers is favoured. If the incompatibility of the hydrocarbon and fluorocarbon moieties is of importance the smectic layers are distorted and at lower temperatures the layer structure is transformed into a columnar structure.
Application of X‐rays to the Study of the Surface Roughness
Authors: Żymierska D. , Auleytner J. 
Published: January 2007

AbstractThe paper presents problems of an application of grazing incidence X‐ray reflectivity as a tool for investigations of the surface roughness. The theoretical calculations are based on Fresnel theory. The surface roughness reduces the reflected amplitude therefore a damping factor describing an influence of that is introduced into equations. The results of computer simulations have been used for estimation of the measured surface roughness of thin epitaxial Si film and GaAs single crystal.
Atomization Energy of the Cu, Ag, Au Crystals in Terms of the Statistical Model
Authors: Sirota N. N. , Sirota I. M. 
Published: January 2007

AbstractThe statistical atom model is used for ab initio calculations of the atom binding energy in crystals. The original calculations by the above method of atomization energy at T = 0 K of the A1 modification crystals of IB elements group of the Periodic System are consistent with the experimental data. The atomization energy estimates of the A2, A3 modifications are made.
Growth and Characterization of CdAl2S4 and CdAl2Se4 Single Crystals
Authors: Krauss G. , Krämer V. , Eifler A. , Riede V. , Wenger S. 
Published: January 2007

AbstractTransparente CdAl2S4‐ und CdAl2Se4‐Einkristalle wurden durch chemischen Transport über die Gasphase in Größn bis zu 15 × 4 × 1 mm3 (CdAl2S4) bzw. 10 mm Kantenlänge (CdAl2Se4) gezüchtet. Die Stöchiometrie der Kristalle wurde mittels Elektronenstrahl‐Mikrosonde überprüft. Strukturelle Untersuchungen nach der Rietveld‐Methode lieferten eine gute Übereinstimmung der gefundenen mit bekannten Strukturdaten. Aus Transmissions‐ und Reflektionsmessungen wurde der Bandabstand unter Annahme einea direkten Halbleiters bestimmt zu: Eg=3.82eV (RT), Eg = 3.94 eV (85 K) für CdAl2S4 und Eg = 2.95 eV (RT), Eg = 3.07 eV (85 K) fü CdAl2Se4.
Growth and Properties of Tetragonal Tungsten Bronze Type Potassium Lithium Niobate Single Crystals
Authors: Xia H. R. , Hu L. J. , Wei J. Q. , Wang J. Y. , Liu Y. G. 
Published: January 2007

AbstractTetragonal tungsten bronze type potassium lithium niobate single crystals with the Nb/Li ratio larger than 3 are grown by the flux pulling method in our laboratory, and it dose not crack when cooling through the paraelectric/ferroelectric phase transition. Crystal growth is studied in two orientations with growth along [100] and [001], and the latter's quality is superior to that of the former. The lattice constants are a = 1.2575 nm and c = 0.3997 nm at 298 K. A Curie temperature is about 480 ± 3°C.
The Crystal and Molecular Structure of Mesogenic Malonates (II)
Authors: Körner H. , Zugenmaier P. 
Published: January 2007

AbstractThe crystal and molecular structures of three diethyl‐2‐{n‐[4‐(4‐nitrophenylazo)‐phenoxy]alkyl}malonate with n = 5 (5 PhNO2), 7 (7PhNO2), 9 (9 PhNO2) and an analogous diethyl‐2‐[4(4‐cyanophenylazo)phenoxy]pentylmalonate (5 PhCN) have been determined with CuKa or MoKa: 5 PhNO2: a = 8.007(6) Å, b = 11.960(8) Å, c = 13.516(9) Å, α = 77.10(6)°, β = 81.80(5)°, γ = 83.15(5)°; R = 0.053; 7PhNO2: a = 8.074(4) Å, b = 11.592(5) Å, c = 14.422(7) Å, α = 87.43(3)°, β = 82.46(3)°, γ = 85.43(3)°; R = 0.072; 9 PhNO2: a = 5.520(5) Å, b = 13.628(9) Å, c = 20.220(11) Å, α = 100.02(4)°, β = 95.49(4)°, γ = 101.02(4)°; R = 0.042; 5 PhCN: a = 8.018(6) Å, b = 11.960(8) Å, c = 13.566(7) Å, α = 77.82(5)°, β = 81.89(5)°, γ = 82.69(5)°; R = 0.067 (isotropically refined). All these structures belong to the triclinic space groups P1.The arrangements of the molecules in the crystal of the homologous series of nPhNO2 suggest two different types of packing independent of n even, odd or large, small. 5 PhCN represents an isomorphous structure to 5 PhNO2. Isomophism between 7 PhNO2 and 7 PhCN was confirmed by cocrystallization of these two compounds whose crystal structure was also determined.
Effect of Fluoride and Sodium Ions on Structural and Thermal Properties of γ‐Al2O3
Authors: Sarbak Z. 
Published: January 2007

AbstractThe structural properties of alumina as well as its fluoride and sodium modifications were characterized by X‐ray diffraction, infrared spectroscopy and differential thermal analysis. We have shown, that fluoride ions interact with hydroxyls type Ia of γ‐Al2O3 forming Al–F species, which then react at 400 °C forming β‐Al2O3. Morever, F/Al2O3 sample heated up to 400 °C contain two acidic hydroxyls type IIa and III, which are also represented on a differential thermal curve as endoeffect with minima at 470 and 500 °C. For Na/Al2O3 sample the same types of hydroxyls interact with Na+ ions leading to substitution of their protons. After heating at 400 °C this sample contains also hydroxyls type IIa and III, which are represented by two endothermal effects with minima at 450 and 520 °C. Differential thermal analysis shown to be a powerful and simple technique to characterize surface hydroxyl types of Na and F samples supported on γ‐alumina.
The effect of boron addition on texture and structure of NiMo/Al2O3 catalysts
Authors: Lewandowski Marek , Sarbak Zenon 
Published: January 2007

AbstractThe effect of support (Al2O3) modification with borate ions and the effect of their concentration on the texture and structure of nickel‐molybdena catalysts were studied. The surface area and pore volume of the samples were determined using the BET method, whereas pores distribution – besides the BET method also by mercury porosimetry. FT‐IR, derivatographic, and diffractometric studies were also performed. Modification with borate ions does not bring about any change in the type of the support pores, nor does it change its crystallic structure. However, a considerable decrease in the surface area of the support was observed. It was shown that modification with borate ions leads to a decrease in thermal stability of catalysts, yet increase in concentration of borate ions raises the thermal stability of the samples. It was found that on the catalyst surface borate ions form a well‐dispersed monolayer structure.