bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth of 2‐methyl‐4‐nitroaniline (MNA) crystals by the bridgman method
Authors: Fukuda T. , Sano T. , Hosoya S. , Yoon D. H.
Published: January 2007

Organic single crystals of 2‐methyl‐4‐nitroaniline (MNA) up to 3 mm in diameter and 20 mm in length have been successfully grown by the Bridgman method using the purified reagent by sublimation. The crystals are transparent and yellow in colour by controlling the growth conditions. In the spectra of yellow coloured crystals no absorption peak is observed until about 450 nm. Also, the crystals of MNA have the two cleavage planes (311) and (010).
Frequency resolved photoconductivity of bulk CdS single crystals
Authors: Belal A. E. , El‐Mongy A. Abd , El Dosoky N.
Published: January 2007

Photoconductivity measurements in CdS single crystal showed that a.c. photoconductivity decays as ω−s, with s value ‐ {1 + α} for ω > 1/τ and ‐ {1–α} for ω < 1/τ. At low frequency values, recombination might be controlled by monomolecular behaviour. As the frequency increases bimolecular behaviour, in shallow states, dominates. Direct recombination is found to be weak dependent on both the intensity and applied voltage. However when band tail recombination is dominant (at higher frequencies), strong dependence is observed.
Enhanced diffusion of phosphorus at grain boundaries in multicrystalline silicon
Authors: Schimpf K. , Palm J. , Alexander H.
Published: January 2007

Two different methods were applied to examine the diffusion of phosphorus at grain boundaries in silicon. Five solar‐cells processed on multicrystalline silicon were investigated. These cells are distinguished by different materials, diffusion‐temperature, and further preparation. Enhanced diffusion at grain boundaries was observed in two of these cells with both methods. One solar cell also showed enhanced diffusion at dislocations. A correlation of the phosphorus diffusion and an enhanced recombination activity of the grain boundaries of these cells is found.
Structure and optical properties of multilayer X‐ray mirrors for long wave part (3.1–4.4 nm) of “water window”
Authors: Fedorenko A. I. , Kondratenko V. V. , Pershin Yu. P. , Poltseva O. V. , Zubarev E. N. , Balakireva L. L. , Didyk V. V. , Burtsev V. V.
Published: January 2007

Structure and optical properties (at λ ‐ 0.154 nm and λ ‐ 3.16 nm) of WTi, WTiN, WSc, and CrSc multilayer X‐ray mirrors for long wave part of “water window”' wavelength range (3.1–4.4 nm) were studied by methods of X‐ray diffractometry and cross‐sectional electron microscopy. The reflectivities at λ ‐ 0.154 nm are increased going from WTiN, CrSc, WTi to WSc multilayers. CrSc mirrors have highest reflectivity and resolution at λ ‐ 3.16 nm. Influence of the ambient atmosphere on optical properties of multilayer mirrors is shown.
EINSTEIN model and modern methods in the statistical theory of crystals
Authors: Zubov V. I.
Published: January 2007

A connection between various methods of the atomic theory of crystals and the EINSTEIN model is analyzed. It is pointed out that despite the oversimplified choice of a unique mode of vibrations for all atoms, in many cases it provides better results than the DEBYE model does. What is more, a number of methods of the theory of strongly anharmonic crystals can be considered as extensions of the EINSTEIN model which in its turn, is their limiting case when the anharmonic terms and interatomic correlations are neglected. A comparison between some peculiarities and results of such methods is drawn.
Growth of the organic nonlinear optical material mnba‐Et (4′‐nitrobenzylidene‐3‐ethylcarbonylamino‐4‐methoxyaniline) crystals by the czochralski method
Authors: Yoon D. H. , Hashimoto M. , Fukuda T.
Published: January 2007

For the first time melt growth of the nonlinear optical organic material 4′‐nitrobenzylidene‐3‐ethylcarbonylamino‐4‐methoxyaniline (MNBA‐Et) by the Czochralski (CZ) method has been carried out to achieve single crystals with large diameter. [100] oriented boules having a diameter of 15 mm and maximum height of 15 mm have been prepared. The structural quality of the CZ crystals is comparable to those from solution growth. The colour of the melt and the grown crystal changes from transparent to opaque as a result of using the same melt for multiple growing cycles deteriorating considerably the optical transmittance.
Growth and characterization of photorefractive Bi12TiO20 single crystals
Authors: Prokofiev V. V. , Carvalho J. F. , Andreeta J. P. , Gallo N. J. H. , Hernandes A. C. , Frejlich J. , Freschi A. A. , Garcia P. M. , Maracaiba J. , Kamshilin A. A. , Jaaskelainen T.
Published: January 2007

Photorefractive Bi12TiO20 single crystals of high optical quality were grown in a resistive heating furnace from high temperature nonstoichiometric (10:1) solutions of Bi2O3 and TiO2 at pulling rates 0.3–0.8 mm/h at rotation 20–30 rpm along the <001> and <011> axis. Powder X‐ray analysis, Laue method, and electron‐probe microanalysis were used for characterization. BTO crystals have the bcc structure of sillenite type with a0 = 10.178(8) Å. The chemical composition of the crystals can be written down as Bi12.1 ± 0.2Tio0.96 ± 0.09O20.1. Natural optical activity ρ of BTO crystals is 6.3 ± 0.2 deg/mm at λ = 0.633 μm and 11.9 ± 0.2 deg/mm at λ = 0.5145 μm, optical absorption coefficient α = 0.42 ± 0.04 cm−1 at λ = 0.633 μm and linear electro‐optic coefficient r41 = r52 = r63 = 5.3 pm/V. Fanning effect in the “fiber‐like” BTO sample was studied and double phase conjugation with conversion efficiency up to 8% was observed in a wide range of incidence angles of the pump at λ = 0.633 μm for 2 × 3 mW input light power.
Crystallization of copper sulphate
Authors: Giulietti M. , Derenzo S. , Nývlt J. , Ishida L. K.
Published: January 2007

Results of the studies of copper sulphate pentahydrate batch crystallization in the temperature range from 70 down to 30 °C are presented. In some of the experiments, free sulphuric acid has been added. The metastable zone width, nucleation and growth kinetic parameters, as well as the system kinetic constant were determined and compared with the data published in the literature.
Growth of bubble‐free Ti‐doped Al2O3 single crystal by the czochralski method
Authors: Fukuda T. , Okano Y. , Kodama N. , Yamada F. , Hara S. , Yoon D. H.
Published: January 2007

The behaviour of bubble entrapment in Ti‐doped Al2O3 single crystals grown by the Czochralski method was studied from the view point of crystal growth conditions such as the crystal rotation rate and kinds of growth atmosphere. The entrapment of bubbles was not correlated with the shape of solid‐liquid interface dependent on crystal rotation rate. We found that the use fo He atmosphere, instead of the conventional atmosphere such as Ar, suppresses the formation of bubbles.
Analysis of the diameteral response of a czochralski crystal II. The melt temperature — furnace temperature relation
Authors: Sveshtarov P. , Gospodinov M.
Published: January 2007

The paper is the second in a series which presentes results on the small‐signal diametral response of a Czochralski crystal grown in a resistively heated furnace to variations in heater temperature and pull rate. Here it is shown that the small‐signal bulk melt temperature variation is related to the small‐signal furnace temperature variation via a first order linear differential equation.
Anisotropic properties of two nematogenic compounds
Authors: Murthy Dr.T. V. S. Arun , Murthy Prof. Dr. V. R.
Published: January 2007

The diamagnetic susceptibilities and optical polarizabilities of two materials that exhibit nematic liquid crystralline phases in the vicinity of room temperature are reported using a molecular vibration approach and a modified Lippincott δ function potential model. The diamagnetic susceptibilities calculated from polarizabilities are also reported.
Effect of Boron Doping in Bi‐based 2223 Superconductors
Authors: Chandra Sekhar M. , Gopalakrishna B. , Kumar M. M. , Suryanarayana S. V.
Published: January 2007

Samples with the stoichiometric composition Bi2−xPbxSr2Ca2Cu3−yByOz (x = 0.3, y = 0.2, 0.25, 0.3, 0.4) ceramics were prepared by a solid state reaction method. The samples were annealed at 850 °C for 100 hours (treatment A), and the other at 850 °C for 200 hours (treatment B). From the X‐ray diffraction data of a ceramic sample it is revealed that all the samples were mixed phases of 2212 and 2223. The variation of the lattice parameters with the dopant level are represented. From the D.C. four‐probe electrical resistivity data it was found that for the samples subjected to treatment B the Tc(0) values were higher than those with treatment A. The A.C. susceptibility data were collected by change in the inductance method. The effect of boron doping on the phase formation and Tc(0) is presented and the volume fraction of the phases estimated from the X‐ray data. The presence of boron in the samples was confirmed by the inductive coupled plasma method. The microstructure of the samples was studied by scanning electron microscopy.
Designing Crystal Morphology by a Simple Approach
Authors: Niehörster S. , Ulrich J.
Published: January 2007

In separation processes containing solids, mostly crystals, the interest in shape modifications of the solids has increased. The idea in it is the necessity to save energy, to achieve specific product requirements, e.g. purities, or to provide downstream processes with better feed material. For an organic crystal a simple way to select a growth inhibitor is presented here, in contrast to the concept of “tailor‐made additives”. The additive selected is structurally different from the host molecule and modifies the habit in a desired manner. The procedure of additive selection involves the analysis of the molecular structure of the crystal to be modified and the orientation of the molecules at the surfaces of the morphological most important faces. Furthermore the problem is discussed if the chosen additive is incorporated into the crystal or not. Results are shown for the system caprolactam/ethanol.
Photoacoustic Spectroscopy of Defect States in Etched and Air‐annealed CuInSe2Single Crystals
Authors: Zegadi A. , Yakushev M. V. , Neumann H. , Slifkin M. A. , Tomlinson R. D.
Published: January 2007

Photoacoustic spectra of cleaved, polished and etched, and air‐annealed n‐type CuInSe2single crystals are measured at different frequencies between 30 and 312 Hz. The spectra related to the bulk of the crystals exhibit five structures due to defects that are also present in p‐type crystals. Polishing and etching as well as subsequent air annealing at 100, 200 and 300 °C reveal rather complex changes of the defect equilibrium in the near‐surface region of the crystals which include both relative concentration changes of existing defects and creation of new defects. The results for polished and etched crystals correspond to trends expected from etching induced local modifications of the composition and structure as revealed by electron spectroscopies and ion channeling. Air annealing is found to affect all existing defects and to create up to five new defects which cannot be explained in terms of the related point defect model proposed by CAHEN and NOUFI.
X‐ray Diffraction Study on MgSeO4. 6 H2O at Elevated Temperatures
Authors: Stoilova D. , Koleva V.
Published: January 2007

The dehydration of MgSeO4. 6 H2O has been studied using an X‐ray powder diffraction method at elevated temperatures. Five different solid phases have been identified in the temperature interval of 20–450 °C: MgSeO4. 6 H2O; MgSeO4. 5 H2O (with a small amount of MgSeO4. 4 H2O), MgSeO4. 2 H2O, amorphous MgSeO4 and crystalline MgSeO4. MgSeO4. 5 H2O crystallizes in the triclinic system with the lattice parameters: a = 6.403(2) Å, b = 10.576(5) Å, c = 6.196(3) Å, α = 98.63(2)°, β = 110.36(2)°, γ = 75.25(3)°, SG P1. MgSeO4. 2 H2O forms orthorhombic crystals with lattice parameters: a = 10.304(1) Å, b = 10.351(9) Å, c = 9.138(9) Å. The crystalline anhydrous magnesium selenate crystallizes in the orthorhombic system with the lattice parameters: a = 4.925(2) Å, b = 9.026(5) Å, c = 6.816(6) Å. Additionally MgSeO4. 4 H2O has been prepared and studied roentgenographically: monoclinic system with the lattice constants: a = 6.064(4) Å, b = 13.773(7) Å, c = 8.062(6) Å, β = 91.82(7)°, SG P21/n. According to expectation the magnesium selenate hydrates are isomorphous with the corresponding magnesium sulphate hydrates.
Thermal Oxidation of ZnS Modifications Sphalerite and Wurtzite
Authors: Schultze D. , Steinike U. , Kussin J. , Kretzschmar U.
Published: January 2007

The oxidation of phase pure ZnS in the wurtzite and sphalerite modification upon heating in an air flow has been studied by simultaneous thermogravimetry‐differential thermal analysis and in‐situ X‐ray diffraction at high temperature (high temperature camera and electron synchrotron).

The oxidation of wurtzite starts at higher temperature, ZnO is formed without any detectable side or intermediate products. Sphalerite oxidation starts at lower temperature, ZnSO4 and Zn3O(SO4)2 are formed intermediately in side reactions yielding finally ZnO.
Infrared Spectroscopic, Thermal and Electromagnetic Studies of Zinc Tartrate Single Crystals Grown by the Silica‐Gel Technique
Authors: Lopez T. , Stockel J. , Peraza J. , Torres M. E. , Yanes A. C.
Published: January 2007

The paper reports on the growth of single crystals of zinc tartrate, by reaction of aqueous solutions of tartaric acid (L +) and zinc chloride in silica gels. The grown crystals have been characterized by X‐ray, infrared spectroscopy, qualitative elemental analysis, thermoanalytical techniques, and electromagnetic studies.
Growth and Characterization of LiNbO3: Mg + Ti Monocrystalline Fibers
Authors: Li Heping , Feng Ziliang , Wang Xiu , Wang Liangshen , Jiao Zhifeng , Xu Xiaofei
Published: January 2007

LiNbO3 : Mg + Ti monocrystalline fibers with a diameter of 200 – 1000 μm have been successfully grown by the laser‐heated pedestal growth method. The lattice parameters, the dopant Mg‐ and Ti concentrations, and the ferroelectric domain structure of the fibers were determined. The results are compared with those in the large crystals grown by the Czochralski method.
Directional Solidification of AlZn Eutectic in Microgravity Conditions
Authors: Pražák M. , Holeček S.
Published: January 2007

The directional solidification of an AlZn eutectic based on the Bridgman method has been carried out on the Earth and in orbit on the Russian orbital station in microgravity conditions on a ČSK‐1 apparatus developed at the Institute of Physics, Czech Academy of Sciences in Prague.

From the conditions of growth — furnace rate 0.1 mm/min, axial temperature gradient in the melt approx. 5 K/cm — the study of the microstructure and the measurements of interlamellar spacing, lamellae thickness α1, hardness HK and the anisotropy of linear thermal expansion it follows, that the microstructure of the specimens prepared in outer space shows an overall lower degree of directionality compared with specimens prepared in analogous terrestrial conditions.
Solid Solutions in the FeNbO4TiO2 System
Authors: Balzer B. , Langbein H.
Published: January 2007

Thermal decomposition of freeze‐dried complex oxalate precursors allows the synthesis of crystalline phases in the FeNbO4TiO2 system at relatively low temperature. This system shows not only a rutiletype, but also a wolframite‐type solid solution (ss), which exists at lower temperatures. The temperature of the reversible transformation wolframite‐rutile decreases with increasing TiO2 content.
The Crystal and Molecular Structure of an Antidepressant Drug (Isocarboxazid)
Authors: İde S. , Topaçli A. , Bayari S.
Published: January 2007

The crystal arid molecular structure of 5‐methyl‐3‐isoxazole carboxylic acid 2‐benzylhydrazine (isocarboxazid, C12H13N3O2), an antidepressant drug, has been determined by X‐ray diffraction method and IR analysis. The compound crystallizes in the monoclinic space group P21/c, with a = 6.376(1), b = 14.131(1), c = 13.256(1) Å, β = 99.75(1)°. The structure has been solved by using SIR program and refined to R = 0.048. The benzene and isoxazoles rings are not coplanar and have a dihedral angle of 167.7(5)° between their respective planes. Some of the bond lengths and angles found in the molecule are distorted due to π‐electron delocalization and strain. The infrared spectrum of isocarboxazid has been also reported and assignments have been suggested for some characteristic bands. These assignments were confirmed by X‐ray analysis.
Crystallization and Thermoelectric Power of Tl2Te3 Single Crystals
Authors: Gamal G. A. , Nassary M. M.
Published: January 2007

Thermoelectric power (TEP) of Tl2Te3 was measured in the temperature range from 150 to 480 K. The crystal was found to have a p‐type conductivity throughout the whole range of temperature. The effective masses of holes and electrons were determined at room temperature and found to be m = 1.1 × 10−34 kg and m = 1.72 × 10−35 kg, respectively. Also at the same temperature the mobility μp was found to be 1737.8 cm2/V.s and μn was 3962.2 cm2/V.s. The hole and electron diffusion coefficients were obtained as 44.84 cm2/s, and 102.23 cm2/s. The relaxation times for holes and electrons were calculated and yielded the values τp = 1.19 × 1012 s and τn = 4.25 × 1013 s, respectively.
Effects of Rare‐Earth Ions on the Quality of a Li–Zn Ferrite
Authors: Rezlescu E. , Rezlescu N. , Pasnicu C. , Craus M. L. , Popa P. D.
Published: January 2007

Effects of the rare‐earth ions on some properties of a lithium‐zinc ferrite used in high frequency are described. A set of seven compounds with formula Li0.3Zn0.4Fe1.96R0.04O4 where R  Yb, Er, Dy, Tb, Gd, Sm and Ce, were prepared by the classical method. The obtained results reveal that, by introducing a relatively small amount of R2O3 instead of Fe2O3, an important modification of both the structure and the properties can be obtained. Curie point, magnetization, electrical resistivity, density, hardness are affected by these substitutions. The effects of rare‐earth ions were explained both by their partial diffusion in the spinel lattice and by the formation of the crystalline secondary phases on the grain boundaries. Densification of the ceramic is attributable predominantly to the relative shrinkage during sintering.

Le travail montre les effets des ions de terre rare sur quelques paramètres d'nne ferrite de LiZn utilisé dans la haute fréquence. Une série des sept compositions avec la formule chimique Li0.3Zn0.4Fe1.96R0.04O4 (R  Yb, Er, Dy, Tb, Gd, Sm et Ce) a été preparée par la méthode classique. Les résultants obtenus montrent que par l'introduction des petites quantités de R2O3 dans le lieu de Fe2O3 une important modification tant de la structure que des propriétés on peut obtenir. La temperature de Curie, l'aimantation, la résistance électrique et densité sont affectés. L'influence des ions de terre rare este expliqué tant par leur partiel diffusion dans la réseau spinel que par leur ségrégation à la surface des cristaux comme phases secondaires. La densification du ferrite est atribué en principal à une relative contraction pendant le frittage.
Spectroscopic and Transport Properties of (NH4)2CuCl4 · 2 H2O Single Crystal
Authors: Narsimlu N. , Sivakumar K. , Sastry G. S.
Published: January 2007

Electron paramagnetic resonance (EPR), Optical absorption and Transport properties of (NH4)2CuCl4 2 H2O single crystals have been studied. An anisotropic g tensor was observed with gl = 2.241 and g∥ = 2.081 by EPR method. The spin orbit coupling constant is found to be 540 cm−1. The optical absorption in UV region are characterized by charge transfer band, in the visible and near infrared region at 13,333, 4,480, 4,336, and 3,998 cm−1 attributed to the transitions between the (d‐d) stark energy levels of the copper (II) ion in an extended octahedral crystal field. Dc electrical conductivity measurements with temperature reveal an anisotropic characteristic of a two‐dimensional layered structure, and exhibits two first order structural phase transitions at about 383 K and 413 K. These transitions are attributed to loss of the two water inolecules of hydration and free rotation of NH+4 ion from a state of torsional oscillation.
Lithium Intercalation into the Tetradymite‐type Selenides Sulfides Bi2Se3‐xSx
Authors: Bludská J. , Jakubec I. , Bezdićka P. , Karamazov S. , Lošťák P.
Published: January 2007

The reaction rate of Li intercalation into Bi2Se3−xSx single crystals (x = 0, 0.025 and 0.05) increases with an increasing sulfur content in the crystals. This effect has been explained qualitatively by a change in the bond polarity in the Bi2Se3 due to the substitution of selenium atoms by sulfur atoms. This substitution results in a change in the electron density distribution and thus also in the width of the van der Waals gap between the structural layers, responsible for the course of intercalation. This explanation is supported by a quantum‐chemical calculation of the charges on the atoms of the Bi2Se3−xSx lattice manifesting and increase in the negative charge on Se atoms with an increasing value of x.
A Novel Coordination Structure of Dichromates Bonding to Copper (II): [Cu(bipy)2(Cr2O7)] · 2 H2O
Authors: Jianmin Li , Yanxiong Ke , Quanming Wang , Xintao Wu
Published: January 2007

Dark‐green multimetal compound crystal [Cu(bipy)2(Cr2O7)]· 2 H2O was obtained from aqueous solution of Cu(NO3)2, K2Cr2O7 and bipyridine. The crystal structure was determined by X‐ray crystallography: triclinic P1, a = 7.716(3) Å, b = 9.656(3) Å, c = 15.517(5)Å, α = 77.41(3)°, β = 81.04(3)°, γ = 82.33(3)°, Z = 2. In this compound, two chromium atoms and a copper atom are linked by two oxo bridges (Cu(II)OCr(VI)OCr(VI)). The copper coordination polyhedron corresponds to a five‐coordinated distorted trigonal bipyramid.
A Structural Study of Aluminate Sodalite Ca8[Al12O24](CrO4)2(CACr)
Authors: Melzer R. , Depmeier W.
Published: January 2007

The structure of the cubic high temperature phase of Ca8[Al12O24] (CrO4)2, CACr, has been determined at 700 K by Rietveld analysis of neutron powder diffraction data. The structure is discussed with respect of those of its homologues. The phase transitions of the title compound have been investigated by means of synchrotron x‐ray powder diffraction and differential thermo analysis. High precision lattice parameters have been determined in the temperature range between 350 and 750 K. Three phase transitions occurring at 610 K, 453 K, and 432 K could be verified. Observed anomalies in the lattice parameters versus temperature might indicate a yet unknown phase transition at about 555 K. This is supported by results of differential thermo analysis.
3D Damage Analysis of Laser‐irradiated Materials inside a Scanning Electron Microscope Using Ion Beam Slope Cutting Technique
Authors: Menzel S. , Hauffe W. , Kadner J. , Wetzig K.
Published: January 2007

In practical use of high temperature materials extreme thermal loads at materials surfaces often occur which can effect a non‐reversible material damage or material failure consequently. These generated damages can be studied using an SEM which is coupled with a pulsed Nd:YAG high power laser. The ion beam slope cutting technique is a very suitable method to produce a highly localized cross section in laser irradiated material. By this the three‐dimensional electron microscopic analysis of the damaged bulk material was possible. For the experiments a combination of ion beam slope cutting and conventional ion etching was used. It enables the high quality of microstructure characterization.
Microhardness‐Plasmon Energy‐Bulk Modulus Relationship in Ternary Chalcopyrite Semiconductors
Authors: Kumar V. , Prasad G. M. , Chandra D.
Published: January 2007

In 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

The 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

Five 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

InxGa1‐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

Single 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

The 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

The 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

The 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

The 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

Thermal 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

The 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

Results 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

The 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

(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

Results 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

The 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

Spontaneous 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

Single 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

A 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

For 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

The 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

The 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

Transparente 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

Tetragonal 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

The 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

The 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

The 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.
Elastic, Piezoelectric and Dielectric Constants of Pentaerythritol
Authors: Ramamoorthy P. , Krishnamurthy N.
Published: January 2007

The elastic, piezoelectric and dielectric constants of pentaerythritol, C(CH2OH)4, have been computed employing the method of long waves and the unscreened rigid ion potential model developed by RAMAMOORTHY and KRISHNAMURTHY. Piezoelectric contribution is taken into account in the computation of elastic constants. This is the first report on the piezoelectric and dielectric constants of pentaerythritol. In the notations followed by LANDOLT‐BORNSTEIN the computed piezoelectric constants are: g14 = 4.82, g15 = 4.37, g31 = 16.21 and g36 = 5.89 (in unit of 10−1Vm/N) and the static dielectric constants are: K1 = 2.38 and K3 = 2.47. The hydrogen bonding in pentaerythritol has no effect on its dielectric behaviour. Calculation of acoustic velocities in piezoelectric crystals and as a special case to the crystals of class 4 is explained in detail. Sound velocities calculated from the elastic, piezoelectric and dielectric constants computed in the present investigation agree with the experimental values determined by the ultrasonic method.
Crystal Structure of Fibrillar Sodium Trimolybdate Hydrate by Powder Diffraction Method
Authors: Łasocha W. , Rafalska‐Łasocha A. , Schenk H.
Published: January 2007

The crystal structure of polycrystalline fibrillar sodium trimolybdate Na2Mo3O10. 3 H2O, has been solved ab initio by Powder Diffraction – Direct Methods package POWSIM. The structure was refined by the Rietveld method with final discrepancy factors RF = 6.9 and Rwp = 17.1%. The structure consists of polymeric chains of Mo‐O polyhedra parallel to the b axis. The space group is C2/m (12), a = 17.179(1), b = 3.7757(3), c = 10.8571(8) Å, β = 115.417(6)°, V = 636.06(6) Å3, Z = 2.