bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal chemistry of the salts Me+Cl · Me2+Cl2 · 2 H2O
Authors: Balarew Christo , Tepavitcharova Stefka
Published: January 2007

The 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

Current‐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

Kinetic 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

Single 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

Pure 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

Crystal 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

Cadmium 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

Experimental 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

Experimental 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

The 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

TlInSe2 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

Ion 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

The 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

α‐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

We 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

A 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

This 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

Photoluminescence 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

Preparation 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

The 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.
The Crystal Structure of Na‐Sulfadimidine
Authors: Patel Dr. Urmila H.
Published: January 2007

The X‐ray crystal structure analysis of Na‐sulfadimidine is reported. Crystals are triclinic. Space group P1 with a = 5.785(2), b = 11.568(1), c = 12.722(2) Å, α = 70.02(1), β = 78.71(2), γ = 77.73(2)° and Z = 2. Crystal structure was solved by direct method to an R‐value of 0.061 for 2441 unique reflections. It is a type of five‐fold coordination complex of Na where Na atom is surrounded by four oxygen atoms and one nitrogen atom: three oxygen atoms and the nitrogen atom belongs to the sulfonyl moiety from three different sulfadimidine molecules and the fourth oxygen atom belongs to solvent water molecule. The crystal structure is stabilized by hydrogen bonds and van der Waals forces.
Effect of Lithium Doping in the Bi‐2212 Superconducting System
Authors: Gopalakrishna B. , Chandra Sekhar M. , Suryanarayana S. V.
Published: January 2007

Samples with the nominal composition Bi2Sr2Ca1–xLixCu2Oy (x = 0.2,0.4, and 0.6) and Bi2Sr2CaCu2−x L1xOz (x = 0.4, 0.6, and 1.0) were prepared by the solid state reaction method. The role of L1 at both Ca and Cu sites in the Bi‐2212 composition were studied. From the X‐ray diffraction data it was found that the L1‐doped at the Ca site increases the c‐axis and that doped at the Cu site decreases the c‐axis. From the D.C. four‐probe resistivity data it was found that Li‐doped at the Ca site reduces the Tc and the L1‐doped at the Cu site gives Tc(0) above the liquid nitrogen temperature. It was observed that the L1 doping reduces the melting point of Bi‐2212 composition. The presence of Lithium was confirmed by inductive the coupled plasma method.
Orthorhombic Polymorph of ErP5O14, Crystal Structure and Characterization
Authors: Katrusiak Andrzej , Kaczmarek Franciszek
Published: January 2007

Erbium pentaphosphate crystals have been characterized and the structure of the orthorhombic polymorph (type III) determined by X‐rays. It has been found that the orthorhombic samples of ErP5O14, space group Pnma, crystallize mainly at higher temperatures and usually are much larger than monoclinic crystals, space group C2/c, obtained from lower‐temperature crystallizations. Differences in fluorescence and upconversion properties between orthorhombic and monoclinic polymorphs have been detected.
Crystal and Molecular Structure of Tosyl Pyrrolidine‐2‐Methanol (C12H17SO3N)
Authors: Sambyal Vinod Singh , Padha Naresh , Goswami K. N. , Bhutani K. K. , Gupta D. K.
Published: January 2007

C12H17SO3N, Mr = 255.33, Orthorhombic, P212121, a = 11.703(1) Å, b = 14.797(3) Å, c = 14.971(2) Å, V = 2592.52 Å3, Z = 8, Dm = 1.309 Mgm−3, Dc = 1.308 Mgm−3, mμ = 21.57 cm−1, F(000) = 1088, T = 290 K, final R = 0.080 for 2416 unique reflections. There are two crystallographically independent molecules in the unit cell of the title compound.
On the Reasons Leading to an Appearance of Correlated and Anticorrelated Dependences of the Minority Carrier Lifetime on the Dislocation Density in Undoped Semi‐Insulating “Stoichiometric” GaAs Crystals
Authors: Glinchuk K. D. , Prokhorovich A. V.
Published: January 2007

It is shown that in undoped semi‐insulating GaAs crystals grown under the stoichiometric conditions both correlated and anticorrelated dependences of the minority carrier lifetime τ on the dislocation density Nd could be observed. The above‐pointed effect is connected with a slight excess of Ga atoms (then the correlated dependence τ vs Nd appears) or of As atoms (then the anticorrelated dependence τ vs Nd appears) which inevitably exists even in “stoichiometric” GaAs crystals (i.e. in GaAs crystals of “stoichiometric” composition).
The Crystal and Molecular Structure of Mesomorphic 1,4‐Dipentadecanoyloxy‐biphenyl (SYM‐14)
Authors: Thyen W. , Kaiser V. , Zugenmaier P.
Published: January 2007

The compound with the general formula CnH2n+1 –COO–C6H4–C6H4–OOC–CnH2n+1, n = 14 (SYM‐ 14) crystallizes in the triclinic space group P 1, with a = 5.431(5), b = 9.346(8), c = 39.172(51) Å, α = 92.60(15), β = 90.65(15), γ = 100.364(8)°.

The crystal structure was solved by direct methods. Least‐squares refinement leads to a final R value of 0.092 for 1575 observed reflections, with I > 2σs(I). The packing arrangement follows the same building principles found recently for the first three members of the well known homologous series of liquid crystalline terephthalylidine‐anilines (TBAA‐n).
Synthesis and Characterisation of Bulk Textured Phases in the Bi(Pb)—Sr—Ca—Cu—O System
Authors: Murugakoothan P. , Jayavel R. , Subramanian C.
Published: January 2007

Growth of lead‐doped textured Bi‐cuprate, using an immersed heater floating zone (TSFZ) apparatus, from a narrow supercooled melt created an essentially dense structure consisting of locally aligned long platelet crystal grains. The extended grains have their long axes parallel to the growth axis with a low angle misorientation. The effect of gas bubbles and the pulling rates on the microstructure and superconducting transition temperature of the textured boules have been studied. The decomposing nature of the 2223 phase on melting leads to form the energetically favourable low Tc 2212 phase.
High Quality InAs1–ySby/InAs Multilayers for mid‐IR Detectors
Authors: Gong X. Y. , Kan H. , Makino T. , Yamaguchi T. , Nakatskasa T. , Kumagawa M. , Rowell N. L. , Wang A. , Rinfret R.
Published: January 2007

The high quality InAsSb multi‐layers have been grown on InAs substrate by Gd‐doped liquid phase epitaxy between 530 and 460°C. Compositional dependence of energy band gap and of lattice constant for epilayers were studied. The material is characterized by surface morphology observation, FTIR transmittance, photoluminescence (PL), spectro‐ellipsometry, and electrical measurements. Surface‐illuminated room temperature p‐n junction photodetectors in 3–5 μm wavelength range have been obtained.
Refined Crystal and Molecular Structure of Andrographolide — Diterpene
Authors: Sambyal Vinod Singh , Goswami K. N.
Published: January 2007

A refined crystal structure of andrographolide has been obtained by X‐ray anaysis using CuKα radiation. It crystallizes in the monoclinic crystal system with unique b‐axis in space group P21. The unit cell parameters are a = 6.552(2) Å, b = 8.009(1) Å, c = 17.989(1) Å and interaxial angle β = 97.32(1)°. The structure has been solved by direct methods and was refined up to R = 0.041, ωR = 0.0464. Both the cyclohexane rings are in chair conformation with the furan ring in twist conformation. The crystal structure is stabilized by hydrogen bonding.
X‐ray Monitoring System for in situ Investigation of Thin Film Growth
Authors: Mikhailov I. F. , Pinegin V. I. , Sleptzov V. V. , Baranov A. M.
Published: January 2007

The X‐ray optical system of in situ monitoring of reflectivity measured in the short‐wave range 0.5–3 Å is proposed. Thickness, density, and microroughness of the growing film are determined for every half‐wave of reflectivity oscillations that corresponds to the averaging by the layer of 10 Å thickness. By the example of diamond‐like film growing, the possibility of an analysis of transition processes and technology failure during film growth have been shown.
Thermodynamic Analysis of Urea Physical Vapour Transport
Authors: Paorici C. , Zha M. , Zanotti L. , Attolini G. , Traldi P. , Catinella S.
Published: January 2007

The vaporisation‐condensation scheme of urea has been investigated in the temperature region below the melting point, in order to establish the thermodynamic reactions on which the physical vapour transport (PVT) of urea is based. By making use of both reported data and experimental results of MS, DTA, DTG, and HPLC analysis, it was shown that PVT relevant reactions are basically molecular sublimation and partial decomposition in solid biuret and ammonia. MS analysis of urea crystals and source residues have also shown that no decomposition can be observed in the growing crystals, unless reheated during growth.

The temperature dependence of the decomposition pressure has been found to be: log10PNH3 [torr] = 38 – 13840/T [K].

The use of this relation in diffusive mass transport calculations brought to linear growth rate values not in disagreement with the experimental values found in closed tube PVT grown crystals.
Electrical Conductivity and Thermoelectric Power of Silver Iododichromate Fast Ion Conducting Electrolytes
Authors: Durga Rani A. N. , Hariharan Dr. K.
Published: January 2007

Fast ion conducting solid electrolytes are becoming increasingly important owing to their application in solid state ionic devices. The present work deals with the silver ion conducting x AgI – (1–x)Ag2Cr2O7 electrolyte system. These electrolytes have been characterised by X‐ray diffraction, electrical conductivity, electronic conductivity and thermoelectric power techniques. A high ionic conductivity of the order of 10−3 S/cm has been observed for the composition mol% 80 AgI–20 Ag2Cr2O7, at room temperature. The electronic conductivity of this electrolyte is three orders of magnitude lower than the ionic conductivity.
Electrical Conductivity and Thermal Dehydration Studies of Mixed Single Crystals of BaCu(C2O4)2 · 6 H2O, Ba1–xCuxC2O4 · 4 H2O and Ba1–2x(NH4)2xC2O4 · 4 H2O
Authors: Kasthuri V. B. , Mohan Rao P.
Published: January 2007

The measurement of electrical conductivity for the investigation of the number of water molecules present in the mixed crystals of barium copper oxalate and barium ammonium oxalate lattice have been carried out in the temperature range 30 to 450 °C. The dehydration temperature and the number of water molecules removed out of the structure at a particular temperature is estimated from the sharp increase in conductivity at these points. The almost steep increase of conductivity is attributed to the increase in the number of mobile charge carriers H+ and OH– ions generated from the escaping water molecules.

The study of electrical conductivity in association with the thermal behaviour has been used to understand the mechanism of conduction.
Phase Analysis of AgI—CuI Solid Solutions
Authors: Popov A. , Iordanova I. , Machkova M.
Published: January 2007

The formation of AgI—CuI solid solution is shown. Several phase transitions are observed in the intermediate compositions which in addition to the high resistivity of the materials present a new ionic conductor.
Precipitation of Catalyst Precursors Theoretical Fundamentals
Authors: Nvlt J.
Published: January 2007

Very high supersaturations, low stability of highly supersaturated solutions, marked secondary changes in the solid phase formed, chemical changes during the ageing of precipitates — this are reasons why our contemporary knowledge on precipitation is far more limited and is also inconsistent compared with mass crystallization of readily soluble substances. In view of this situation, it seems to be highly desirable to show the general fundamentals which could lead us to systematic understanding of the various cases apparently unrelated with each other.
An Exponential‐Hyperbolic Crystal Growth Rate Model
Authors: Mydlarz Jerzy
Published: January 2007

A new exponential‐hyperbolic size‐dependent crystal growth rate function G (L) = Gm (eaL–b)/(eaL – c) is proposed. The model has been examined in detail for the direct determination of size‐dependent crystal growth rates from the cumulative number oversize distribution of continuous Mixed‐Suspension Mixed‐Product Removal (MSMPR) crystallizers using both simulated and realistic data, both for systems that hold and that violate McCabe's Δ law, respectively. It is show that direct fitting of cumulative number oversize distribution data using the proposed model gives an improved estimation of effective crystal growth rates over the whole size range during MSMPR crystallization compared with previous models tested.
Neutron and Synchrotron Radiation High Pressure Experiments on Aluminate Sodalite Sr8[Al12O24](CrO4)2
Authors: Melzer R. , Depmeier W. , Vogt T. , Gering E.
Published: January 2007

High pressure powder diffraction experiments were carried out on the aluminate sodalite Sr8[Al12O24] · (CrO4)2 using a miniature clamped cell with neutron radiation at the ILL and a diamond anvil cell with synchrotron radiation at Hasylab/Desy. The results of both experiments agree well. Lattice parameters were determined up to a pressure of 7.2 GPa. The average linear compressibility amounts to 4.3 · 10−3 GPa−1, which corresponds to a linear bulk modulus of 233 GPa. The observation of superstructure reflections could be related to two new phase transitions. The first one occurs between 0.37 and 0.5 GPa, the second one at about 2.0 GPa. A final measurement at ambient pressure revealed the reversible character of the pressure induced phase transitions.
A New Modified TGS Crystal
Authors: Fang C. S. , Liu H. , Zhuo H. S. , Wang M. , Xu D.
Published: January 2007

Triglycine sulfate (TGS) crystals doped with Cr6+ have been grown from a growth solution with various Cr6+ concentrations. The structure, transmission spectrum, pyroelectric properties, and the photorefractive effect of the crystals have been measured. It has a high internal bias field and photorefractive effect.
SEM Observation of Nucleation and Growth of Ag Crystallites on Graphite Substrate
Authors: Gotoh Yoshihiko , Horii Akira , Ishii Toshio , Kawanowa Hitoshi , Yumoto Hisami , Gonda Takehiko
Published: January 2007

“In‐Situ” observation of nucleation and growth of Ag crystallites on graphite substrate by vapour deposition was carried out by scanning electron microscope (SEM). Irradiation of the SEM electron beam onto the substrate surface before and during deposition enhanced Ag nucleation. The density of the Ag crystallites was 1010/cm2 in room temperature condensation, but decreased to 109/cm2 in high temperature condensation at 140 °C. When the substrate was heated after room temperature condensation, the density of the Ag crystallites decreased prominently. This means that coalescence of the Ag crystallites takes place as a result of their migration on the substrate.
Crystal Structure of a Complex of Sarcosine with Barium Chloride
Authors: Krishnakumar R. V. , Natarajan S.
Published: January 2007

Single crystals of sarcosine barium chloride tetrahydrate were crystallised from a saturated aqueous solution containing stoichiometric amounts of sarcosine and barium chloride, in 2: 1 proportion. The intensity data were collected using a CAD‐4 diffractometer with graphite monochromated MoKα radiation. The crystal data are as follows: a = 7.235(1) Å, b = 10.668(4) Å, c = 15.686(3) Å, V = 1210.7 Å3, F.W. = 369.33, dexpt, = 2.02 g · cm−3, dcalc = 2.026 g · cm−3, Z = 4 and the space group is P212121. The structure has been solved to an R value of 0.02 for all the 1239 reflections with I > 2σ(I). The sarcosine molecule exists as zwitterion in the structure. The barium ion is found to have 10‐fold coordination with nine oxygens and a chlorine taking part in coordination. All the water oxygens and chlorines take part in hydrogen bonds except carboxyl oxygens.
Pressure Dependence of C–V Curve for Ferroelectric PbTiO3 Thin Films Prepared by RF Multi‐target Magnetron Sputtering
Authors: Cho C. R. , Jang M. S. , Jeong S. Y.
Published: January 2007

Lead titanate thin films were prepared in‐situ by RF magnetron sputtering method in the substrate temperature region of 550 °C ˜ 650 °C using Ti and Pb metal targets and oxygen gas. The films deposited at 650 °C for 60 min – when the applied power to the Ti and Pb target and deposition pressure were 200 W, 40 W, and 1.8 × 10−2 Torr, respectively — had stoichiometric composition ratio and shown X‐ray diffraction patterns of tetragonal structure like that of the powder.

For the application to the piezoelectric field effect transistor (PI‐FET), the substrate of SiO2 (50 nm)/p‐Si(100) was used. Leakage current density of the thin film was 7 × 10−8 A/cm2 at 100 kV/cm, dielectric breakdown voltage was 1.8 MV/cm, and so it showed high insulator characteristics. Capacitance‐voltage curve was measured as a function of pressure. The variation width of the capacitance was 6.5 pF at bias voltage of –4 volts, and the value increased linearly according to the pressure up to about 6 kgf/cm2, and was saturated at the pressure of 8 kgf/cm2.
Crystallization Kinetics of Sodium Perborate
Authors: Livk Ing.I. , Smodiš Ing.M. , Golob Prof. Dr. Ing.J. , Pohar Prof. Dr. Ing. sc.C.
Published: January 2007

Some basic physicochemical properties of aqueous sodium perborate solutions, essential in designing an effective control, were measured. The kinetics of primary nucleation was determined by the measurement of the metastable zone width. The differential method was applied for the determination of the crystal growth rate equation. It was found that the solubility and the nucleation rate constants are in very good agreement with the literature data whereas the parameters of the growth rate equation show an influence of the experimental conditions.
Temperature Oscillations in Eutectic Alloy Melt for the Bridgman‐Stockbarger Configuration
Authors: Pražák M. , Holeček S.
Published: January 2007

The characteristics of the temperature field in AlZn, AlGe, PbSn, and Sb—InSb low‐melting alloy eutectics were determined by means of the Bridgman‐Stockbarger method of directional solidification with a specimen fixed in a graphite ampoule and a moving furnace. The device could be rotated in such a way, that an arbitrary angle α between the axial temperature gradient in the melt and the gravity field vector could be set.

Periodic and/or nonperiodic temperature fluctuations indicating periodic and/or nonperiodic turbulent convection up to an angle α = 80° were studied in the individual systems. At larger angles laminar convection can be expected. The frequency of the temperature oscillations is the same along the entire length of the specimen, whilst the amplitudes of the temperature oscillations depend on the situation of the measurement in the specimen.

It has been found that the zone of unstable periodic convection is reduced with an increase of the axial temperature gradient and a decrease of the H/d ratio for a cylindrical ampoule. The convection instability threshold in the ampoule increases with the deviation of the ampoule axis from the axis of the vertical unstable arrangement, i.e. from the direction of the gravity vector. The threshold of the laminar flow instability and the onset of turbulent flow increases with the H/d ratio, i.e. an ampoule with a higher H/d ratio stabilizes laminar flow.
Structural Studies of Some Zinc‐ and Calcium Sulfide Phosphors
Authors: Sen D. K. , Bhushan S.
Published: January 2007

The XRD studies of CaS : Cu,Cl; ZnS · Cu,Cl; (Zn + Ca) S : Cu,Cl, and (Zn + Ca) S · Cu, La,Cl showed the presence of materials like CaSO4 and ZnO. However, the explanations given earlier (SEN, BHUSHAN) on the origin of different bands observed in the electroluminescence spectra of these materials remain valid.
Chiral Symmetry Breaking in Sodium Chlorate Crystallization from Unstirred Solution
Authors: Szurgot Marian , Szurgot Jadwiga
Published: January 2007

Statistics of nucleation of chiral forms of sodium chlorate from unstirred, achiral solutions was studied. The trimodal distribution of enantiomers was obtained in which apart from the peak for the same probability of the creation of L and D crystals, two other maxima for the large enantiomeric excesses of L and D forms were present. The first nucleated crystals govern the handedness of the secondary crystals and the formation of pure enantiomers and high enantiomeric excesses in crystallization from unstirred, unseeded solutions are caused by the process of chiral symmetry breaking rather than statistical fluctuations.
On the Diffusion Anisotropy of Polycrystals
Authors: Divinski S. V. , Larikov L. N.
Published: January 2007

A model of diffusion anisotropy appearance in a textured polycrystalline aggregate under the grain boundary diffusion preponderance (the C type of kinetic) has been suggested. Although in the textured polycrystal there exists a distribution over 5 degrees of freedom describing the grain boundaries macroscopically, it is the misorientation distribution that has been shown to may give rise to the diffusion anisotropy. Presence of small‐angle boundaries and a certain, sufficiently sharp texture is the key moment at this.
Forced Electrostrictive Vibrations of Cubic Crystals
Authors: Kloos G.
Published: January 2007

A problem of experimental research in quadratic electrostriction is the question how the observed strain signal, induced by a high electric field, is influenced by sample mounting. An analytical treatment of the case of a cubic crystal is demonstrated that allows one to find a relationship with material constants and strains that may occur at the bottom of the sample. To find functions that fulfill the given boundary conditions an approach similar to that used to solve the problem of the elastic cube with Somigliana boundary conditions has been employed.
Formation of Three‐dimensional Microelectronic Structures by Molecular Beam Eitaxy Combined with Ion Beam Procedures
Authors: Thomas A. , Ramirez A. , Zehe A. , Brückner V.
Published: January 2007

The progress in microelectronics is characterized by an increasing density of functional elements on the wafer. This is first of all a result of a reduction of lateral dimensions in patterned geometries. Nevertheless, further progress on this way is limited by a number of reasons, e.g. residual impurities in the ingot materials, physical phenomena, as diffusion processes between adjacent layers as well as electron migration inside electronical structures. Finally, the lithographic means of structuring implies disadvantages which limit the minimization progress.

One way to overcome these problems consists in three dimensional structuring of microelectronical objects. Thereby, the third dimension is introduced by growing of thin layers which are again structured in their lateral dimension. This can be done by molecular beam epitaxy (MBE) in combination with Ion Beam (IB) procedures.

The present paper gives an overview on materials which exhibit epitaxial growth on Si. The utility of CaF2 for three dimensional structuring by use of ion bombardment will be described. As another example, the conversion of materials will be discussed. For instance, insulating CaF2 can be converted into conductive CaSi2 by help of Si+‐ion implantation.
X‐ray Structure Analysis of 4–[(3,3–Dimethyloxiranyl)–methoxy]‐7H‐furo[3,2‐g][1]benzopyran‐7‐one
Authors: Singh Attar , Gupta Vivek K. , Rajnikant  , Goswami K. N.
Published: January 2007

The title compound, C16H14O5, a furanocoumarin crystallizes in the triclinic space group P1. The unit cell parameters are a = 7.852(2), b = 8.485(1), c = 11.095(1) Å; α = 105.90(1), β = 103.18(2), γ = 95.07(1)°. The structure has been solved by direct methods. Final R = 0.048 for 1943 observed reflections. The furanocoumarin system is almost planar. The epoxide ring makes a dihedral angle with the fused ring system of 98.21(11)°. Molecules are held together by C—H… O hydrogen bonds.
DTA, DSC, and X‐ray Powder Diffraction Studies on Some Zinc Selenate Hydrates
Authors: Koleva V. , Stoilova D.
Published: January 2007

The thermal dehydration of ZnSeO4 · 6 H2O, ZnSeO4 · 5 H2O, and ZnSeO4 · 3 H2O has been studied by TG, DTA, and DSC‐analyses. It has been established that the dehydration of ZnSeO4 · 6 H2O occurs stepwise and as intermidiate hydrates ZnSeO4 · 5 H2O, ZnSeO4 · 3 H2O and ZnSeO4 · H2O are produced. The enthalpy of dehydration of the observed phase transitions has been determined. The enthalpy of formation of ZnSeO4 · 6 H2O, ZnSeO4 · 5 H2O, ZnSeO4 · 3 H2O, and ZnSeO4 · H2O has been calculated on the basis of the DSC‐data. ZnSeO4 · 5 H2O and ZnSeO4 · 3 H2O have been studied rentgenographically: ZnSeO4 · 5 H2O crystallizes in triclinic system with lattice parameters: a = 6.387(2) Å; b = 10.706(3) Å; c = 6.167(3) Å; α = 98.66(2)°; β = 109.32(3)° γ = 75.52(3)° V = 384.3(2) Å3; SG P1. ZnSeO4 · 3 H2O forms orthorhombic crystals with lattice constants: a = 8.165(4)Å; b = 11.314(5) Å; c = 12.465(7) Å; V = 1151.5(7) Å3; SG Pbca.
Reactivity at Line Defects in Antimony in Etchants with Dextro‐ and Levo Tartaric Acid
Authors: Raval Amit H. , Joshi Mihir J. , Shah B. S.
Published: January 2007

The (111) cleavage faces of antimony single crystals were etched in aqueous mixtures of fuming nitric acid plus dextro tartaric acid and fuming nitric acid plus levo tartaric acid. Triangular, crystallographically oriented etch pits were observed at sites of dislocations. The activation energies for lateral motion of ledges and the frequency factors were calculated for both types of etchants which were found to be higher in levo tartaric acid containing etchants than in dextro tartaric acid containing etchants. The results are explained in terms of antimony complexes and the difference in the shape of dextro tartaric acid and levo tartaric acid molecular structures.
Dependence of Transient and Steady State Creep on Grain Size in Aged Al‐10 wt% Zn Alloy
Authors: Youssef S. B. , Beshai M. H. N. , Fawzy A. , Sobhy M. , Saad G.
Published: January 2007

The effect of grain size as well as ageing temperature on the creep characteristics of Al‐10 wt% Zn alloy have been studied. It has been found that the steady state creep rate ε decreases by increasing grain size, whereas it increases by increasing ageing temperature. It is suggested that the decrease of ε may be due to the change in the density of mobile dislocations in addition to the change in concentration of point defects and impurity atmospheres. An empirical formula ε = ml−2 + c has been proposed to correlate the creep rate and grain size. The values of the activation energies controlling the creep processes corresponded to that required for dislocation glide.
Effect of Ultrasonics on Agglomeration
Authors: Nývlt J. , Žáček S.
Published: January 2007

Crystal size distribution of potassium aluminium sulphate dodekahydrate prepared under various conditions has been used for characterization of the degree of agglomeration of crystals. Six series of batch precipitation experiments with batch times from 2 to 80 minutes have been represented by a) dried crystals, b) the same crystals partially de‐agglomerated before the measurement, c) wet crystals taken directly from the batch, d) the same crystals partially de‐agglomerated before the measurement, e) wet crystals taken directly from the batch occurring under ultrasonic action, and f) these crystals partially de‐agglomerated just before the measurement. Degree of agglomeration decreases in this sequence.
Size Effect and Processes of Interdiffusion in Multilayer Films
Authors: Protsenko I. , Odnodvoretz L. , Petrenko S. , Chornous A.
Published: January 2007

The electrophysical properties of multilayer structures consisting of the alternate Co and Ni layers or Co and Cr layers obtained in high vacuum (˜ 10−3 Pa) were investigated.

The size dependences of the temperature coefficient of the resistance (TCR) of the films were obtained experimentally and then compared with the R. Dimmich theoretical model. The analysis shows that the main reason of the difference between theoretical and experimental data of TCR is the interdiffusion of atoms from one layer to another.
Transition from Isometric to Skeletal Crystal Shapes
Authors: Tonchev V. , Nanev Chr. N.
Published: January 2007

The transition from isometric to skeletal shapes during crystal growth under diffusion hindrances in matter supply has been considered as an orientational phase separation, bringing to energetically more stable surfaces. The critical deviation from the close packed crystallographic orientation and the transition time have been estimated on the basis of a simple model.
Self‐destruction of Hills of Growth on the (001) Face of TGS Single Crystal
Authors: Bikov A. Z.
Published: January 2007

The phenomenon of self‐destruction of the hills of growth on the (001) face of a TGS single crystal is registered experimentally. A mechanism of this phenomenon is proposed.
Characterisation of the Six‐coordinated Octahedral Site in Cd(C4H2O4) · 2H2O Crystals
Authors: Ravikumar R. V. S. S. N. , Reddy S. N. , Rao S. N. , Reddy B. J. , Reddy Y. P.
Published: January 2007

Optical absorption spectra of Co(II) and Ni(II) doped cadmium maleate dihydrate (CMDH) are recorded at room temperature and liquid nitrogen temperature. The UV–VIS–NIR spectra are characteristic of the transition metal ions in solids. The results and analyses of the spectra indicate near octahedral site symmetry for cobalt ion and trigonally distorted octahedral site symmetry for nickel ion. The following crystal field parameters are derived.

The IR spectra are characteristic of the host lattice CMDH.
Stacking Fault Energy of Silicon Carbide (SiC) Polytypes
Authors: Momeen  , Khan M. Y.
Published: January 2007

A polytypic material grown under similar thermodynamic conditions occurs in several phases which are included as ordered and disordered ones. These phases occur with a minimum free energy difference ≅ kT. This relative free energy (stacking fault energy) has been evaluated here using different methods.
Dilatometric Analysis and HK Hardness Measurement of Directionally Solidified AlZn Eutectic Specimens
Authors: Pražák M. , Holeček S.
Published: January 2007

Two simple and relatively fast methods have been verified of an objective inference of the quality of the directionality of the volume structure of a specimen. The above methods can thus be conveniently added to classical metallography and image analysis.

AlZn eutectic appears to be an appropriate model system due to a linear thermal expansion anisotropy of the directionally solidified specimens, which is given by the expansion anisotropy of a directionally positioned β‐Zn phase with a hexagonal lattice. The thermal expansion is lowest in the growth direction of the lamellae.

The hardness is anisotropical on the surface. The HK hardness is anisotropical with respect to the position of the indentor in the structure. The hardness shows an overall increase with the growth rate of the specimen (i.e. with the fineness of the structure) and its value its always lowest, when the longer diagonal of the HK indentor is parallel with the lamellae on the cross sections of the specimens.
Long‐term Crystal Growth under Microgravity during the EURECA‐1 Mission (I) THM Growth of AlxGa1−xSb
Authors: Danilewsky A. N. , Lauer S. , Bischopink G. , Benz K. W.
Published: January 2007

Long‐term crystal growth experiments were successfully performed under microgravity conditions during the first flight of the unmanned mission EURECA‐1 in the automatic mirror furnace (AMF). Two crystals of AlxGa1−xSb with [001] and [111] orientation respectively were grown from gallium solution by the travelling heater method. The grown length of the single crystals is 4.0 mm and 4.2 mm respectively. The space‐grown samples show a high microscopic homogeneity which indicates the absence of time dependent convection. From pulse markers a constant growth rate of 0.6 ± 0.1 μm/min is measured which is lower than 0.8 ± 0.1 μm/min obtained in earth grown reference samples. Details about the experiment performance and the growth results are given.
The Effect of Different Inorganic Salts on the Growth Rate of NaCl Crystallized from Sea Water
Authors: Zhang S.‐B. , Yuan J.‐J. , Mohameed H. A. , Ulrich J.
Published: January 2007

A comprehensive experimental study on the effect of fourteen different inorganic salts on the growth rate of NaCl single crystals is presented. The fourteen different inorganic salts are chosen as they are present in Chinese sea water. The impurity content of each salt has been varied according to its presence in the natural sea water. The impurities are differentiated in groups related to their effect on the growth rate of NaCl. The examined impurities are: MgCl2 · 6 H2O, KCl, SrCl2, NaBr, Nal, NaF, Na2SO4, NaBO2 · 4 H2O, Na2CO3, Na2SiO3 · 9 H2O, ZnSO4, CuSO4 · 5 H2O, PbCl2, and K4Fe(CN)6.
Crystal Structure of 6,6′‐dimethoxy‐2,2′‐diphenyl‐19‐crown‐5 Hg(SCN)2
Authors: Ochando L. E. , Amigo J. M. , Costero A. M. , Pitarch M. , Debaerdemaeker T.
Published: January 2007

The crystal structure of 6,6′‐dimethoxy‐2,2′‐diphenyl‐19‐crown‐5 Hg(SCN)2 has been determined from three‐dimensional X‐ray diffraction data. The compound crystallizes in the triclinic space group P1 (no 2) with unit cell parameters α = 9.712(6) Å, β = 11.137(7) Å, c = 14.768(12) Å, α = 86.04(5), β = 80.36(4), γ = 65.70(4), Z = 2, V= 1435(2) Å3. The structure was determined by direct methods which on refinement yielded a final value of R(F) index as 0.068.