bluuebunny/crossref_metadata_2025_split huggingface dataset:
Densities, refractive indices, and order parameters of a binary liquid‐crystalline system with an induced smectic A phase
Authors: Hauser A. , Ernst S. , Hamann A. , Pelzl G. 
Published: January 2007

AbstractFor the binary mixture of 4′‐Nitrophenyl 4‐n‐octyloxybenzoate and 4‐n‐Octyloxyphenyl 4′‐pentyloxybenzoate with an induced smectic A phase the refractive indices (nc and no) and the density were measured in dependence on the temperature. The orientational order parameter and the density were calculated using a mean field fitting method. In the induced SA phase the refractive indices and the calculated orientational order parameters are showing only a weak dependence on concentration. The calculated and measured densities are in the same order of magnitude.
Crystal growth and characterization of Rb0.3K0.7TiOPO4
Authors: Wang J. Y. , Wei J. Q. , Liu Y. G. , Shao Z. S. , Shi L. P. , Haussühl S. 
Published: January 2007

AbstractSingle crystal growth and characterization of Rb0.3K0.7TiOPO4 are reported. After improving the technological procedures of crystal growth, high‐quality large single crystals were obtained. The refractive indices, pyroelectric coefficient, dielectric, piezoelectric, elastic, thermoelastic and elastooptic constants, SHG efficiency and damage threshold were measured.
Study of optical and transport properties of K2CuCl4 · 2H2O single crystal
Authors: Narsimlu N. , Srinivasu D. , Sastry G. S. 
Published: January 2007

AbstractOptical absorption, transport properties and EPR of K2CuCl4 · 2H2O single crystals have been studied. The optical absorption in UV, and visible region are characterized by a charge transfer band, and in the near infrared region at 3998, 4336, and 4480 cm−1 are attributed to transitions between the stark levels of copper(II) ion in an extended octahedral crystal field. An anisotrophic ‘g’ value was observed with g∥ = 2.12 and g∥ = 2.24 by EPR method. The spin orbit coupling constant is found to be 500 cm−1. D.C. electrical conductivity measurements with temperature reveal an anisotropy characteristic of a two‐dimensional layered structure and exhibit a first order irreversible structural phase‐transition at 377 K, i.e. from tetragonal to monoclinic crystal system. X‐ray diffraction studies and density calculations from the crystal structure data in both the phases suggest that the first order irreversible transition occurs following the loss of the two water molecules of hydration.
Mass transport in the three‐thermal‐zone solute transport method
Authors: Guan Qingcai , Wang Jiyang , Wei Jingqian , Liu Yaogang , Ma Xiaoshan , Jiang Minhua 
Published: January 2007

AbstractThe mass transport process of the three‐thermal‐zone solute transport method is analyzed theoretically in this paper. The growth rate of a crystal is depending on the temperature gradient and the size of the curcible. Comparing with the normal temperature gradient solute transport method, this technique can be used to grow crystals in better quality.
Twinning of crystals as a result of differences between symmetrical and energetical most favourable structure arrangements
Authors: Krafczyk S. , Jacobi H. , Follner H. 
Published: January 2007

AbstractIt is thought that the building units of crystal structures always tend to the highest possible symmetrical arrangements. These arrangements have not to correspond in every case to the energetical most favourable structure. Structures that show this distinct misfit tend to twinning. The examination of pentaerythrite and 1,2,4,5‐tetrabromobenzene, two substances usually existing as twins, leads to the finding of structures–by lattice‐energy calculations–with a better energy balance, but are not known yet as autonomous phases. Both cases showed arrangements with lower symmetry explaining the transition between the twin individuals. Following this theory the development of crystal twins is based on a structural instability caused by the conflict between the more favourable energetical arrangement and the highest available symmetry.
Structure and growth morphology of RF‐sputtered superthin niobium films
Authors: Mikhailov I. F. , Borisova S. S. , Fomina L. P. , Babenko I. N. , Melnik N. N. , Pudonin F. A. 
Published: January 2007

AbstractSuperthin niobium films of 3 to 35 Å thickness prepared by radio‐frequency sputtering have been studied by modern X‐ray methods, such as reflectometry, fluorescence analysis and grazing beam structure analysis. It has been shown that the films were polycrystalline and consisted of several layers of niobium oxides and solid solution NbO. Two simple models were used to describe erly stages of film growth. In the stage of island growth the complete oxidation of Nb to Nb2O5 is inevitable. Beginning from effective thickness ∼ 5 Å the deposited film becomes continuous, and further, layer‐by‐layer growth takes place.
Some observations of growth hillocks and growth layers on potassium hydrogen tartrate crystals
Authors: Sangwal K. , Veintemillas‐Verdaguer S. 
Published: January 2007

AbstractSome observations of growth hillocks and growth layers on the as‐grown surfaces of potassium hydrogen tartrate (KHT) crystals obtained at 30 °C from aqueuos solutions of different supersaturations are reported and discussed. It is found that macrospirals, isolated growth hillocks, and growth layers are typical features observed on these crystals. Bunching of rectilinear growth layers originating from growth hillocks produced parallel macrosteps on the {010} faces. In certain cases, interaction of thick rounded layers of unequal height, emitted from neighbouring strong sources, gave rise to residual steps (pseudo‐interlaced steps). Isolated growth hillocks produced by microbes were also observed.
Conformation of simple aromatic molecules
Authors: Ahmed N. A. , El‐Shaabieny A. , Abbas Y. , Atia W. M. , El‐Kholy M. 
Published: January 2007

AbstractThe conformation of five aromatic molecules were calculated using the atom‐atom potentials method. The deformations of valency angles were not considered, and the conformations of some molecules were determined solely by the minimum interaction energy between non‐bounded pairs of atoms. In case of molecules having π‐bonds, the geometry of the isolated molecule was determined by the balance between the π‐electron and the non‐bonded energies. A comparison is made between the structure of molecules in the crystal form and the structure of the free molecules determined by conformational analysis. For terphenyl molecule which has different structures in the different phases, a calculation of the structure of molecule in crystal from was done theoretically using lattice energy minimization. Good agreement was found between structures obtained theoretically and experimentally.
Crystal and molecular structure of p‐methane triol(C10H20O3)
Authors: Sambyal Vinod Singh , Goswami K. N. , Singh Tej P. , Thappa R. K. 
Published: January 2007

AbstractThe compound crystallizes in the monoclinic crystal system with the space group P21, having cell parameters a = 8.533(2) Å, b = 10.388(2) Å, c = 6.195(2)°A, β = 92.17(1)°. The structure has been solved by direct methods and refined upto R = 0.076. The six membered cyclo hexane ring is in chair conformation with maximum deviation 0.2296 Å for the C(1) atom. The molecules are held together by hydrogen bonding.
Vibrational spectra and phase transition in triglycine sulpho‐phosphate
Authors: Joe I. Hubert , Aruldhas G. , Anbukumar S. , Ramasamy P. 
Published: January 2007

AbstractInfrared and single crystal Raman spectra for various polarization geometries of Triglycine Sulpho‐Phosphate (TGSP) have been recorded and analysed. The bonds of hydrogen atoms in H2SO4 and H3PO4 groups are shown to be weak and the possibility of proton transfer from H2SO4/H3PO4 group is indicated. Two different types of glycinium ions are shown to be present in the unit cell. Temperature dependent Raman spectra of TGSP have been recorded. The phase transition detected around 325 K in TGSP is explained in terms of the flipping motion of the glycinium ion and of attaining a higher crystal symmetry.
Coloured zirconia
Authors: Römer H. , Luther K.‐D. , Assmus W. 
Published: January 2007

AbstractThis paper deals with the growth of coloured zirconium oxide crystals, cubic stabilized with yttrium oxide. The host material–zirconia–is colourless. To generate colourations minor concentrations of 3d‐ and 4f‐elements are incorporated into the lattice. The resulting colours are dependent on the ions' valence and the local crystal symmetry. Both, the possibility to change the ions' valence by heat treatment, and the possibility to change the local crystal symmetry by alteration of the starting yttria concentration, are discussed in the following.
Crystal chemistry of the salts Me+Cl · Me2+Cl2 · 2 H2O
Authors: Balarew Christo , Tepavitcharova Stefka 
Published: January 2007

AbstractThe crystal chemistry of the double salts Me+Cl · Me2+Cl2 · 2 H2O (where (Me+ = K, Rb, Cs; Me2+ = Mn, Fe, Co, Ni) is considered. It is concluded that these salts crystallize in three types of structures, the Me+ ion size being decisive for the structure type.Salts containing the large Cs+ ions crystallize in an orthorhombic structure in which [Me2+ (H2O)2Cl4] octahedra form chains having common Cl− corners.Salts with the smaller K+ ions crystallize in a tricline system, the [Me2+ (H2O)2Cl4] octahedra being connected by a common Cl–Cl edge and forming dimers.When the intermediate in size Rb+ ions are present in the salts, either of the above structures is possible as well as a monoclinic structure which is intermediate in symmetry.The expected isostructure of the cesium salts was checked by studing the CsCl · NiCl2 · 2 H2O–CsCl · MnCl2 · 2H2O–H2O system. A continuous series of mixed crystals is found.
Behaviour of switching phenomena in single crystals of TlGaTe2
Authors: Nassary M. M. , Hussein S. A. , Nagat A. T. 
Published: January 2007

AbstractCurrent‐voltage characteristics measured on TlGaTe2 single crystals reveal switching effects at temperatures below 263 K. The current‐voltage characteristics are symmetric with respect to the polarity of the applied field. The threshold parameters for switching are found to depend on temperature, illumination intensity and sample thickness.
On the kinetics of GaAs chemical transport and epitaxy in the system GaAs–I2
Authors: Hitova L. , Lenchev A. , Trifonova E. P. , Apostolova M. 
Published: January 2007

AbstractKinetic analysis of experimental data on transport and epitaxial growth of GaAs with iodine in closed and in open tube systems has been carried out. The uniformly shrinking core model has been applied to study GaAs transport kinetics in the closed system. The kinetics of GaAs epitaxy in the open one is interpreted according to a model which assumes that in the initial stage of chemical reactions new phase nuclei are formed instantly at a constant number of active centers and that the nuclei grow isotropically.
Synthesis and crystal structure study of Y2O3 high‐pressure polymorph
Authors: Skrikanth V. , Sato A. , Yoshimoto J. , Kim J. H. , Ikegami T. 
Published: January 2007

AbstractSingle crystal high pressure polymorph of yttria was synthesized for the first time using a link–type cubic anvil apparatus. Crystal structure was refined from single crystal data. High pressure polymorph was confirmed as a monoclinic phase. Lattice parameters of the high pressure polymorph at room temperature and ambient pressure were determined as follows: a = 13.8714 Å, b = 3.4487 Å, c = 8.5862 Å, β = 100.12°.
Laser‐induced phase transitions in PbI2
Authors: Chaudhary S. K. 
Published: January 2007

AbstractPure crystals of PbI2 have been grown using zone‐refining system. The structural phase transition 12 R → 2 H has been observed when exposed to ruby laser light. The results have been explained on the basis of structural considerations of PbI2 and compared with the earlier existing findings in literature.
Imaging crystal growth features using scanning force microscopy (SFM)
Authors: Kipp S. , Kämmer S. , Lacmann R. , Rolfs J. , Tanneberger U. , Beckmann W. 
Published: January 2007

AbstractCrystal growth features on stearic acid, potassium nitrate, and potash alum have been determined by means of scanning force microscopy (SFM). Structures like growth spirals, etch pits, 2D‐nuclei, and growth hillocks could be observed. The analysis of the face specific surface topographies leads to structures which correspond to those expected from kinetic measurements.
Use of cadmium selenide thin films as a carbon dioxide gas sensor
Authors: Patel N. G. , Panchal C. J. , Makhija K. K. 
Published: January 2007

AbstractCadmium Selenide (CdSe) thin films were prepared in different growth conditions by thermal evaporation. The films were characterised using transmission electron microscopy and X‐ray diffraction. The electrical parameters such as resistivity, carrier mobility, and concentration were determined. The sensitivity of carbon dioxide (CO2) gas on CdSe thin films were studied. A tentative mechanism was proposed, in which the role of CO2 gas in increasing the conductivity of CdSe thin films were explained by Molecular Orbital (MO) theory. CO2 gas sensing alarm system was fabricated.
Study of growth kinetics of ammonium oxalate monohydrate crystals from aqueous solutions
Authors: Mielniczek‐Brzóska E. , Sangwal K. 
Published: January 2007

AbstractExperimental results of the dependence of linear growth rates of ammonium oxalate monohydrate [(NH4)2C2O4· H2O; AO] single crystals on solution supersaturation are presented. The AO crystals were grown by constant‐temperature, constant‐supersaturation method at 30 and 40 °C in the supersaturation range of 1–9%. It was observed that the supersaturation dependence of growth rates follows the parabolic growth law. Analysis of the supersaturation dependence of linear growth rates of AO crystals showed (1) that growth models involving surface diffusion and direct incorporation of growth units give kinetic parameters similar to those reported for other compounds grown from solutions, and (2) that the the BCF model of cooperating screw dislocations is also applicable. An inverse relationship between the estimated values of the length,L, of the line containing the dislocations and growth rate,R, and a direct relationship betweenLand interplanar distance,dhkl, of the face {hkl} were found. Both these relationships are associated with the process of generation of screw dislocations in the growing layer.
Experimental investigations of buoyancy‐driven convection in vertical (BixSb1−x)2Te3 molten zones
Authors: König F. , Röstel R. , Kuhl R. 
Published: January 2007

AbstractExperimental results for various states of buoyancy driven flow in vertical (Bi0.23Sb0.75)2Te3 molten zones with covered surface are presented. Critical thermal wall Rayleigh numbers Ra for the onset of time‐dependent convection have been determined by means of temperature measurements. The stability diagram obtained for the existing buoyancy driven convection shows the increase of Ra with increasing aspect ratio. This relation is also known from other crystal growth configurations and is due to the damping influence of container walls. At the beginning in the oscillatory region of convection extremely long periods of oscillation (maximum 850 s) were observed, which are caused by another mechanism than periods (25 … 37 s) registered at increasing melt heights. Furthermore, Bi0.5Sb1.5Te3 crystals were grown by using the vertical zone melting technique. The microscopic striations observed in the grown crystals correlate exactly with the temperature signals caused by time dependent convection. However, the fluctuations of the tellurium distribution in axial direction measured by scanning the Seebeck coefficient are presumably generated by unsteady solutal convection during growth.
Temperature variation of lattice parameter and thermal expansion of TmAl2
Authors: Rao B. Appa , Kistaiah P. , Murthy K. Satyanarayana 
Published: January 2007

AbstractThe lattice parameter of TmAl2 has been measured from room temperature to 637 K using CuKα‐radiation. The data have been used to evaluate the coefficient of thermal expansion at various temperatures. It was found that the lattice parameter increases while the coefficient of expansion remains constant throughout the range of temperature studied.
Composition variations of lattice parameters of TlIn(Se1 – x)2, TlIn(Se1 – xSx)2, and TlIn1 – xGaxSe2 mixed crystals
Authors: Gasanly N. M. , Özkan H. , Çulfaz A. 
Published: January 2007

AbstractTlInSe2 and TlInTe2 crystallize in a tetragonal cell (space group 14/mcm) (MÜLLER et al.). A primitive cell of these ternary crystals contains two formula units. All the Tl atoms in these compounds are univalent. The In atoms are trivalent being in a tetrahedral environment consisting of Se or Te atoms. InSe4 or InTe4 fragments of a unit cell form the chains extended along c‐axis coinciding with [001] directions. Such chains are bonded to each other by Tl atoms.TlGaSe2 and TlInS2 crystals belong to the monoclinic system (space group C2/c) (MÜLLER, HAHN; WONG‐NG et al.). The primitive cell of these crystals contains eight formula units. The lattice of TlGaSe2 crystals consists of strictly periodic two‐dimensional layers arranged parallel to the (001) plane. Each successive layer is turned through a right angle with respect to the previous one. The fundamental structural unit of a layer is the Ga4Se10 polyhedron representing a combination of four elementary GaSe4 tetrahedra linked together by bridging Se atoms. The Tl atoms are in trigonal prismatic voids resulting from the combination of the Ga4Se10 polyhedra into a layer. The Tl atoms form nearly planar chains along the [110] and [110] directions.
Ion channeling study of defects in CuInTe2 single crystals
Authors: Yakushev M. V. , Neumann H. , Tomlinson R. D. 
Published: January 2007

AbstractIon channeling spectra of as‐grown CuInTe2 single crystals are measured using a 2 MeV 4He+ analysing beam. It is found that the measured minimum yields cannot be explained within a model of randomly distributed non‐interacting point defects caused by deviations from ideal stoichiometry. A model with extended defects due to vacancy clustering and dislocation formation is proposed to interprete the experimental results.
X‐ray electrono‐optical and SIMS characterization of Si crystals implanted with Bi ions before and after rapid thermal annealing
Authors: Auleytner J. , Adamczewska J. , Barcz A. , Górecka J. , Regiński K. 
Published: January 2007

AbstractThe purpose of the presented paper is to find out what kinds of information on surface layer structure of implanted silicon after rapid thermal annealing can be acquired by such non‐destructive methods as X‐ray diffractometry and its complementary RHEED technique.The experiments were performed on Si crystals implanted with Bi ions.The studies showed that using the anomalous X‐ray transmission of the wavelength of 1.54 Å we are able to determine the defect concentration introduced by ion implantation with different doses as well as the effects of defect annealing.It was also shown using the REED that the surface layer of ca. 50 Å thick remains amorphous after RTA probably due to the oxidation. The measurements by using SIMS pointed also out that at the crystal surface there was a small amount of Bi atoms accumulated after RTA.
Investigation of characteristics of activation energy of α‐LiIO3 crystals by dielectric breakdown
Authors: Wang Xiu , Zhu Jianbin , Xu Xiaofei 
Published: January 2007

Abstractα‐LiIO3 crystal is an essential quasi‐one‐dimensional ionic conductor, and its ionic conductivity is typically anisotropic. The activation energy of α‐LiIO3 has been calculated by the dielectric breakdown method. The calculating result shows that the anisotropism of the activation energy is consistent with that of conductivity.
Crystal structure of an unusual four‐coordinated copper(II) complex containing 1,10‐o‐phenanthroline and salicyclic acid crystal structure containing Cu(II) o‐phen and salicyclic acid
Authors: Jianmin Li , Jianbing Zhang , Xuefei Huang , Shaowu Du , Xintao Wu 
Published: January 2007

AbstractWe have synthesized a multi‐ligand chelate copper(II) complex [Cu · (C7H5O3] · (C12H8N2) · H2O1 · (C7H6O3)· NO3, and determined its structure by X‐ray diffraction method. The space group of the title compound is P21/a. It is monoclinic, with a = 14.227(4), b = 9.627(4), c = 19.008(7) Å, β = 102.06(3)·, Z = 4. The two salicyclic acid molecules in the cell are in different environments, one inner, the other outer. The geometry around Cu(II) is a four‐coordinated distorted plane square. The two coordinating atoms are two nitrogen atoms from phenanthroline, one oxygen atom from salicyclic acid, one oxygen atom from water.
A New Structural Model for Lithium Niobate
Authors: Vyas J. C. , Kothiyal G. P. , Ghosh B. , Gupta M. K. 
Published: January 2007

AbstractA new model based on the crystal field theory is proposed for LiNbO3. According to this the central position of the Nb ions in oxygen octahedra is energetically unstable leading to the splitting of the potential energy curve into the one having two equivalent off‐centered minima. The phase transition temperature Tc is related to the average height of the barrier existing between these energy minima. The model explains satisfactorily some of the properties of LiNbO3 in the paraelectric and ferroelectric phases, which were not fully understood by earlier models.
Electric twinning in quartz by temperature gradient
Authors: Iliescu B. , Chirila R. 
Published: January 2007

AbstractThis paper presents a new method for obtaining electric twins in quartz crystal: thermal treatment in a temperature gradient at about 500 °C, that means under phase transition point. + 5X quartz crystal plates for resonators were used; a temperature gradient of 15–25 °C was applied for 4–5 hours along the Y axis (the place length). For + 5X resonators, the diminution of the resonant frequency and the increase of the inductance were plotted as a function of the level of twinning.
Raman and photoluminescence analyses of the crystalline InAlAs layer grown on InP substrate
Authors: Jiang G. C. , Juang Y. D. , Chyi J. J. , Lu S. , Chang L. B. 
Published: January 2007

AbstractPhotoluminescence and Raman measurements are used to characterize the InxAl1‐xAs (0.48 < × <0.573)epilayers grown on InP substrate by molecular beam epitaxy. It is found that as In composition, x, deviates too much from 0.52, misfit dislocations may be introduced. These dislocations will dramatically reduce the radiative efficiency of the InAlAs epilayers. Raman spectra become broader and more asymmetry due to alloy potential fluctuations as the mismatch becomes large.
Luminescence of SnO2: Eu; dependence on the oxidation state of the precursor
Authors: Kynev K. , Gutzov S. , Peneva S. K. , Apostolov A. A. 
Published: January 2007

AbstractPreparation conditions and phase composition of polycrystalline SnO2: Eu luminophores are investigated. The results show that the luminescence intensity of SnO2: Eu obtained from Sn(II)‐containing precursors, (hydroxide or oxide), is considerably higher than that from Sn(IV) oxide hydrate. It is considered that the creation of luminescence centers in SnO2: Eu is connected to the formation of intermediate Sn(II)—Sn(IV) oxides during the oxidation.
Crystal structure of R(–)–1–Tosyl–2–methylpyrrolidine
Authors: Gupta Vivek K. , Goswami K. N. , Gupta D. K. , Bhutani K. K. 
Published: January 2007

AbstractThe crystal structure of R(–)‐1‐tosyl‐2‐methylpyrrolidine has been determined by X‐ray structure analysis. The compound crystallizes in the monoclinic space group P21 with cell parameters a = 7.858(1), b = 14.929(6), c = 11.128(1) Å, β = 105.42(1)°. The structure has been solved by direct methods and refined to R = 0.046. There are two crystallographically independent molecules A and B in the asymmetric unit. The pyrrolidine ring of molecule A is disordered with atom C4 occupying two possible sites. The S atom has a distorted tetrahedral coordination in both the molecules. Two bifurcated hydrogen bonds are observed. Molecules are held together by hydrogen bonds.