bluuebunny/crossref_metadata_2025_split huggingface dataset:
Far Infrared and Raman Optical Study of CdInGaS4, CdIn2S4, HgInGaS4 and CdIn2S2Se2 Crystals
Authors: Syrbu N. N. , Radautsan S. I. , Cretu R. V. , Tezlevan V. E. , Moldoveanu N. A. 
Published: January 2007

AbstractRaman and infrared reflectivity spectra of CdInGaS4, CdIn2G4, HgInGaS4, and CdIn2S2Se2 crystals have been investigated. The fiindamental phonon parameters, the limiting dielectric constants ϵ0 and ϵ∞ and the reflectivity spectrum contours have been calculated using classical dispersion relations.
Elastic Behaviour of Some Substituted Nickel ferrites
Authors: Rao K. Vishnu Prasad , Purushotham Y. , Chandel J. S. 
Published: January 2007

AbstractThe longitudinal and shcar wave velocities of some substituted nickel ferrites Ni1.05Sn0.05Fe1.9‐x (Cr or Al)xO4 were determined at room temperature by the pulse transmission technique. The elastic moduli have been corrected to theoretical density. A linear relationship between Debye temperature and average sound velocity has also been observed.
High‐temperature Localization of Plastic Deformation in Lithium Fluoride Single Crystals
Authors: Skvortsova N. P. 
Published: January 2007

AbstractExperimental results on the superlocalization of plastic deformation at high strains and high temperatures in LiF single crystals are described. The physical conditions of transition to a localized plastic flow in the temperature range of 603 K to 1073 K T (0.53–0.94Tmp) using constant strain rate compression tests under strain rates from 10−3s−1 to 10−2s−1 are found. The results indicate that the deformation mechanism involves dislocation climb, controlled by diffusion. The connection of high temperature flow instability with an excessive concentration of point defects (strain vacancies) in zone of shear has been confirmed.
On the Behaviour of Thermoacoustic Parameters in Liquid Crystals
Authors: Reddy R. R. , Ahamed Y. Nazeer , Kumar M. Ravi , Rao T. V. R. 
Published: January 2007

AbstractThermoacoustical parameters of liquid crystals are evaluated in terms of the coefficient of volume expansivity. The MOELWYN‐HUGHES parameter has been utilized to estimate a number of thermoacoustical parameters namely the isothermal, isobaric, and isochoric Grüneisen parameters, the repulsive exponent of intermolecular potential; the molecular constant, the fractional available volume, the Sharma constant, and Anderson‐Grüneisen parameter for a few liquid crystals at different temperatures. At the transition temperature when the mesogen transists from a highly disordered isotropically liquid state to a more ordered and dense nematic state, α exhibits a high value and this high value in α causes a sharp fall in S0 and enables to establish the transition temperatures more precisely is mesogen. It is noticed that S0 also exhibits pretransitional temperature as α does. In all these systems the S0 parameter, which is a characteristic constant imparts, on the average a constant value of 1.11 ± 0.01 both in the isotropic and nematic phases. The general behaviour of other thermoacoustical parameters have been clearly demonstrated.
Studies on the Structure of alpha‐Quinacridone
Authors: Lincke G. , Finzel H.‐U. 
Published: January 2007

AbstractAlpha‐quinacridone crystallizes in the triclinic space group P1withZ= 2,a= 14.934 ± 0.064 Å,b= 3.622 ± 0.004 Å,c= 12.935 ± 0.040 Å; α = 91.39 ± 0.28°, β = 107.13 ± 0.02°, γ = 92.84 ± 0.24°. The molecules are connected by hydrogen bonds more far from linearity (≈145°) than gamma‐quinacridone 162°). Together with π‐π bonds, building molecular stacks along the short axisb= 3.622 Å, both types of bonds run through the whole lattice. Molecules within the hydrophobic planes exhibit orientational disorder. Transitions between gamma‐ and alpha‐quinacridone has been discussed: all inversion centers are retained, only the vectors of bravais lattice and the angles of molecules in the stacks are changed. The calculated pattern of alpha‐quinacridone is compared with the experimental one by means of overlay‐ and difference plots. – The transition character of the alpha‐quinacridone is stressed by generation of a combined pattern of 50% alpha‐ and 50% gamma‐quinacridone, calculating an experimental alpha‐quinacridone.
Speed Dependency of Abrasion during AFM‐Scanning under High Load
Authors: Wolf B. , Paufler P. 
Published: January 2007

AbstractThe paper discusses general questions of friction and wear from the point of material sensitivity in AFM studies. The depth of generated grooves after scanning under high load proved a tool of material characterization. The erosion depth was found to sensitively depend on the scanning speed. A model for quantitative discussion of this phenomenon is presented, which also explains the relation between external load and lateral friction force.
Research of the Central Core in Bi12SiO20Crystals
Authors: Gospodinov M. , Tassev V. , Dimitrov K. 
Published: January 2007

AbstractThe structure of the so‐called “central core” within Czochralski grown Bi12SiO20crystals is investigated by the laser projection. A finer structure with a number of optical inhomogeneities with irregular forms and sizes about 2–3 μm is observed within the core. The conditions for facet growth and absorption of impurities on the facets are described. Positron lifetime measurements are carried out within and outside the core. The results show a higher concentration of defects in regions within the core. The optical rotatory power in regions within and outside of the core was measured, too. An evaluation of the distribution of the different structural units and the dopants is made. Some suppositions about the kind and the role of the defective center are given.
Thermoanalytical and X‐ray Studies of Rapidly Solidified K2CO3
Authors: Vassilev G. P. 
Published: January 2007

AbstractMolten K2CO3 was rapidly solidified, and investigatcd using DSC, X‐ray analysis and infrared spectra. All thermoanalytical investigations have been carried out in the temperature interval from 20 to 450 °C. The sorption of water by the anhydrous potassium carbonate is the reason for appearance of K2CO3 · 1.5 H2O in the specimens. The desorption processes occur in two stages usually. The enthalpics of desorption were estimated to be about 23000 J/mol. The polymorphic phase transitions of K2CO3 were studied and compared with literature data.
Single Crystals of Cubic Ferrite Containing Only Fe3+ as Magnetic Ions
Authors: Rezlescu E. , Rezlescu N. , Craus M. L. , Pasnicu C. , Rezlescu L. 
Published: January 2007

AbstractSingle crystals of LiFe5O8 and Y3Fe5O12 are of considerable interest for microwave applications. These were grown by spontaneous crystallization from fluxed melts by slow cooling. The quality of the obtained crystals were analyzed by X‐ray diffraction and by measuring of the characteristic parameters (saturation magnetization σs, Curie temperature Tc, density D, hardness Hv). Although the both ferrites involve Fe3+ as the only magnetic ions which are responsible for the magnetic properties of these ferrites, several essential differences are found attributing to the particularity of their crystalline structure.Les cristaux de LiFe5O8 Y3Fe5O12 suscitent un considerable interět pour les applications dans le domain de microondes. Le developpement des cristaux est provoqué par la cristalisation spontane, pendant le procesus de mélange des flux fondus, en regime de refroidissemnet lent. La qualité de ces cristaux ainsi obtenus a été analisée à l'aide de la diffraction des rayons X et du messurement des paramètres caractéristiques (magnetisation de saturation σs, température Curie Tc, dénsité D, dureté Hv). Quique les deux ferrites impliquent les Fe3+ comme les seuls ions résponsables pour les proprietés magnétiques, beaucoup d'autres differences sont trouvées provenant de la particularité de leur structure cristalline.
Surface Smoothing of Copper Single Crystals Using POM (Potential Oscillating Method)
Authors: Kipp S. , Lacmann R. 
Published: January 2007

AbstractThe deposition of metals is a process to get metallic coatings on metals. The potential oscillating method (POM) allows dissolution and deposition processes in parallel. Using this method the crystal's habit becomes more perfect, and the equilibrium form can be obtained. It is mostly dominated by the {111}‐ and the {100}‐face, as usual for cubic face centered crystals. The crystallographic faces develop more clearly and become smoother. This paper deals with the determination of the ideal conditions for the electrochemical experiment using copper single crystals, and the analysis of the surface topography using light microscopy, and scanning force microscopy.
Dependence of the Electric Properties and the Positron Lifetimes on the Dopant Content in La‐doped SrTiO3
Authors: Tang C. Q. , Xia Zhengcai , Yao Shude , Chen Shouyuan 
Published: January 2007

AbstractThe resistivity, the dielectric constant, and the positron lifetimes in La‐doped SrTiO3 have been measured for La content x of 0—10 at.%. It was found that with increasing x, the variations of the resistivity and the dielectric constant and the positron lifetime parameters are nonmonotonic. The positron experiments have shown that the La‐doping induces mainly formation of Sr vacancies and variation of Sr vacancy configuration; the most probable configuration is the isolated Sr vacancies (V) as x < 0.5 at.%, the associated defects (La V) for 0.5 < x < 1 at.%, and the associated defects (2 La V) above x = 1 at.%. The results suggest that the variation of the resistivity can be regarded as variation of electron density, and the variation of the dielectric constant results mainly from variations of the space‐charge polarizaion and Sr‐vacancy concentration and configuration.
Growth and Characterization of Urea‐(DL) Tartaric Acid Single Crystals
Authors: Lü M. K. , Meng F. Q. , Yang Z. H. , Yu W. T. , Zeng H. 
Published: January 2007

AbstractA new organic UV nonlinear optical crystal urea‐(DL)tartaric acid [CO(NH2)2−(DL) C4H6O6] (abbreviated as U(DL)T) is reported. Large single crystals have been grown from aqueous solution by the cooling method. They belong to the monoclinic space group P21 and the lattice parameters are: a = 7.6973 Å, b = 23.3310 Å, c = 4.8727 Å, and β = 100.82°. The structure and some of its physical properties have been determined. The crystal is transparent from 0.24 to 1.95 μm. The efficiency of powder SHG is larger by one order of magnitude than that of KDP. Thus the crystal will be a useful NLO material.
Silicon Tubes for Microelectronic Applications Grown Directly from the Melt
Authors: Vanca V. , Dinu M. , Enache V. , Schlett Z. 
Published: January 2007

AbstractA die‐free technique for growing large diameter silicon tubes (5–15cm) directly from the melt has been developed. The attained result was a constant tube wall thickness for a range of 7 to 0.2 mm at 1500 mm length limited by the equipment pulling stroke. It is shown that the inner pressure of the tube is function of the meniscus height at the growth interface. A speed is also presented. By means of experiments the thermal gradient at the solid‐liquid interfaces is determined.
Microstructures on Zirconium Trisulphide Single Crystals
Authors: Patel S. G. , Agarwal M. K. , Arora S. K. 
Published: January 2007

AbstractPhysical vapour transport grown single crystals of zirconium trisulphide have been examined by optical microscope, and the study of growth patterns on their finished surfaces reveal the screw dislocation mechanism by which the crystals have grown.
The Crystal and Molecular Structure of 4‐Hydroxy‐4′‐nitro‐ biphenyl and its Potassium Salt
Authors: Pfeil A. , Zugenmaier P. 
Published: January 2007

AbstractThe crystal and molecular structures of the title compounds have been solved by single crystal X‐ray analysis. 4‐Hydroxy‐4′‐nitro‐biphenyl (NBO) crystallizes in the centrosymmetric, monoclinic space group P21/n witha= 6.036(4) Å,b= 12.392(3) Å,c= 13.346(8) Å, β = 96.46(3)° and 4 molecules in the unit cell. Its potassium salt (NBOK) similarly belongs to P21/a witha= 11.277(2) Å,b= 7.3606(6) Å,c= 14.383(3) Å, β = 107.804(7)° and also 4 molecules in the unit cell. The structure of NBO was refined by full matrix least‐squares calculation toR= 0.043 for 1105 observed reflections, the structure of NBOK toR= 0.041 for 2288 observed reflections, respectively.NBO and NBOK crystallize in layer‐like structures. The biphenyl molecules of NBO are arranged as corrugated ribbons in layers. The ionic and polar moiety of NBOK (potassium, oxygen, and crystal water) are separated by biphenyl units to form layers. The almost planar biphenyl units of NBOK are arranged in pairs and exhibit a short molecular distance of 3.08 Å within one pair.
Effect of Cu Ions on the Dipole Moments and Polarization of Strontium Barium Niobate Single Crystals
Authors: Xia H. R. , Wang C. J. , Yu H. , Chen H. C. , Song Y. Y. 
Published: January 2007

AbstractThe crystal growth, the ferroelectric hysteresis loops, and the infrared reflectivity spectra of coppermodified strontium barium niobate (SBN) single crystals are reported. Compared with the undoped SBN crystals, the copper‐modified crystals have stable hysteresis loops, the spontaneous polarization of which is about 0.30 C/m2, but that of the undoped SBN crystals is only about 0.12 C/m2. Their coercive field strength is all about 340 V/mm. The experimental results of the infrared spectra show that the infrared reflectivities vary as the orientations of the dipole moments owing to the copper‐doping. The c‐axis becomes the most stable orientation of the dipole moments, and the polarization will be locked and won't recede if the copper‐modified crystals are polarized into monodomains.
Oblique Phonons in Raman Scattering and IR Reflection of TeO2 Crystal
Authors: Syrbu N. N. , Cretu R. V. , Cebotari V. Z. , Mushinskii V. P. 
Published: January 2007

AbstractThe Raman scattering and IR reflectivity have been investigated for different crystal configurations. The contours of reflectivity spectra have been calculated. The angle dependence of polar vibrational modes in both reflectivity and Raman spectra have been investigated. The peculliarities of the transition from longitudinal mode to transverse one and vice versa both with and without changing of symmetry have been obtained. The phonon parameters and effective ionic charges of the anions and cations have been determined. It has been shown that there exists an effective ionic charge anisotropy of the oxygen and tellurium ions.
Mechanosynthesis and Mechanolysis of Solid Solutions of La2O3 with Some Rare Earth Oxides
Authors: Todorowsky D. , Terziev A. , Minkova N. 
Published: January 2007

AbstractThe effect of the mechanoactivation on Y2O3, Nd2O3 and CeO2, on mixtures of La2O3 with each of these oxides as well as on the solid solutions La2O3–CeO2 is studied. The activation causes a decrease of the individual oxides' unit cell parameters. The formation of solid solutions of La2O3 with the oxides studied is found. Under the conditions of activation in air no decomposition of La2O3–CeO2 solid solution is detected. The solution is, however, destroyed when the activation is carried out in the presence of acids.
Voronoi Polyhedra: A Useful Tool to Determine the Symmetry and Bravais Class of Crystal Lattices
Authors: Bohm J. , Heimann R. B. , Bohm M. 
Published: January 2007

AbstractA handy PC‐supported method will be described to deduce the Bravais lattice (Bravais class) of a crystal lattice from an arbitrary set of lattice parameters. The method involves the construction of the related Voronoi polyhedron (Dirichlet domain, Wirkugsbereich, Fedorov parallelohedron, Wigner‐Seitz cell) whose metric relations between its edge lengths can be used to unequivocally identify the Bravais lattice. This is particularly useful if an unconventional setting of the unit cell, or inaccurately determined lattice parameters may result in misleading conclusions as to identify the correct Bravais lattice.
Anchoring Energy of Some Nematic Liquid Crystals at Aligment Layers of Different Topography
Authors: Frunza S. , Roques Y. , Farenc J. , Stoenescu D. N. , Traverse J. P. 
Published: January 2007

AbstractUsing a high electric field method, the anchoring energy was measured for tilted homogeneous cells filled with nematic liquid crystals (5CB, ZLI 1132). These cells contain aligment layers of five different types obtained either by SiO depositions at various incidence angles or by special polyvinylic alcohol (PVA) coatings. The observed differences in the anchoring energy values are due to the differences in the layer topography.
MOVPE growth of spontaneously ordered (GaIn) and (AlIn)P layers lattice matched to GaAs substrates
Authors: Gottschalch V. , Franzheld R. , Pietzonka I. , Schwabe R. , Benndorf G. , Wagner G. 
Published: January 2007

AbstractA systematic study of the metal‐organic vapour‐phase epitaxial growth of (GaIn)P and (AlIn)P layers deposited on GaAs substrates with (001) and (110) orientation is presented. Special attention has been paid to the growth on (001)‐oriented wafers with different misorientations to the growth direction. The influence of the growth conditions on the properties of the epitaxial layers such as lattice mismatch, alloy composition, photoluminescence (PL) wavelength, FWHMs of PL peaks and atomic ordering is discussed. Layers with mirrorlike surfaces and various degrees of order could be deposited at growth temperatures Tg ranging from 595 °C to 750 °C for (GaIn)P and 720 °C to 800 °C for (AlIn)P. In addition to the influence of Tg on the Ga incorporation during the (GaIn)P growth we found the Ga distribution coefficient kGa to be affected by the misorientation of the substrates. kGa correlates presumably with the number of kinks and steps on the substrate surface.Transmission electron diffraction (TED) and PL investigations show that the degree of order — often described by the ordering paramter η — depends strongly on Tg the ordering is more pronounced when the layers are deposited on substrates misoriented towards the (111) lattice plane. Strong ordering has been observed for (GaIn)P samples grown at 680 °C on substrates 2° misoriented towards the [110] direction and at 650 °C on substrates 6° misoriented towards the same direction. For the (AlIn)P samples striking ordering has been found when they were grown at 720 °C.
Graphical Representation of Various Models for Crystal Size Distribution in Continuous Flow Crystallizers
Authors: Nývlt Jaroslav , Hostomský Jiří 
Published: January 2007

AbstractPlots of crystal size distribution of the following crystallizer models are compared: an ideal continuous‐flow MSMPR (mixed suspension, mixed product removal) crystallizer with a zero as well as non‐zero initial crystal size, an MSMPR crystallizer with size dependent growth of crystals, an MSMPR crystallizer with missing fines, an MSMPR crystallizer with agglomerative growth, and a series of MSMPR crystallizers simulating a crystallizer with nonideal agitation. The shape of the individual size distribution curves can serve as a diagnostic criterion in determination of the most probable model of crystallization.
Study of Imperfect Iron Doped NiAl Crystals with Laue Method
Authors: Zhang Hui , Zahn Gernot , Paufler Peter 
Published: January 2007

AbstractBy using an imaging plate, point defects and lattice distortion prior to and after plastic deformation has been studied with back reflection Laue method. This includes structure refinement with the intensity data extracted from back reflections only. Preliminary results show promising prospect. The intrinsic difficulties of Laue method have been addressed. Improvement possibilities will also be discussed.
Formation and Structure of TiZn‐Oxides
Authors: Steinike U. , Wallis Bettina 
Published: January 2007

AbstractIn powder mixtures of ZnO and TiO2 the compounds Zn2TiO4, ZnTiO3 and Zn2Ti3O8 can be formed as a result of solid state reactions. The mechanism of the double oxide formation is essentially determined by the microstructure of the powder mixture. Furthermore, the kind of the double oxide depends on the TiO2‐modification. There exist structural similarities between Zn2TiO4 (spinel) and TiO2 (anatase) on the one hand and ZnTiO3 and TiO2 (rutile) on the other hand. The compound Zn2Ti3O8 is formed only on the basis of the Zn2TiO4‐phase. The crystal structure of Zn2Ti3O8 was derived as a defect spinel. The unoccupied sites of cations are not arranged statistically, but they are ordered in the structure. This order leads to the decrease of the space group symmetry from Fd‐3m to P4332.
Vapour‐liquid‐solid Growth and Characterisation of N‐methylurea Crystals
Authors: Zha M. , Zanotti L. , Zuccalli G. , Ardoino M. , Capelletti R. , Paorici C. 
Published: January 2007

AbstractA new growth method, based on a vapour‐liquid‐solid (VLS) mechanism, is reported for preparing single crystals of N‐methylurea (NMU), a material which appears to be a good alternative to urea for non‐linear optical applications in the “near UV‐visible” region of the spectrum. Details of the growth procedure are given and it is shown that large single crystals, with volumes up to 7 ÷ 10 cm3, can be obtained with satisfactory reproducibility and very fast growth rate. Structural and optical characterisation, still preliminary, are reported, which evidence a crystalline quality comparable to that of urea and N‐methylurea as previously grown with other growth techniques. Cryst. Res. Technol., Vol. 32, No. 1.
Characterisation of Bi2Se3 Crystals Highly Doped with Pb
Authors: Karamazov S. , Horák J. , Navrátil J. , Lošták P. 
Published: January 2007

AbstractPb‐doped Bi2Se3 crystals were prepared from starting elements Bi, Se and Pb of 5N purity in the concentration interval cpb = 0 – 4 × 1025 Pb atoms m−3 by a modified Bridgman method. The measured values of the transmittance and reflectance were used to determine the dependence of the absorption coefficient K on the photon energy for crystals with various values of cpb and to prove the shift of the short‐wavelength absorption edge with cpb. On the basis of the assumption of the validity of the “single valley” model, which can describe the lowest conductivity band of Bi2Se3, and using the values of the freecarrier effective mass in the directions perpendicular and parallel to the trigonal axis c we determined the value of the reduced Fermi energy η 300 K for crystals with various values of cpb. Using the value of η, we calculated the dependence of the Seebeck coefficient on cpb and compared it with the experimentally determined values. The comparison has shown that the increasing content of Pb atoms in the Bi2Se3 lattice leads to a suppression of the role of the mechanism of scattering by ionised impurities; at higher concentrations of Pb in the crystal the mechanism of scattering of free carriers by acoustic phonons becomes dominant. Further, the ideas on the nature of the point defects in the Bi2Se3(Pb) crystals are presented and the “anomalous” dependence of the free‐electron concentration on cpb is qualitatively accounted for.
Growth of the New Infrared Nonlinear Optical Crystal DCNP
Authors: Fang L. , Fang C. S. , Zhuo H. S. , Sherwood J. N. 
Published: January 2007

AbstractThis paper reports on the growth of 3‐(1,1‐dicyanothenyl)‐1‐phenyl‐4,5‐dihydro‐1 H‐pyrazole (DCNP) crystals in dimethylformamide. The effect of different solvents on the growth of DCNP has been investigated. Dimethylformamide was found to be a good solvent, Transparent DCNP single crystals were grown from this solvent. They are a promising infrared nonlinear material.