bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth Kinetics of High‐Tc and Low‐Tc Phases in Bi2‐xPbxCa2Sr2Cu3Oy Superconducting Compounds
Authors: Rao D. Mangapathi , Somaiah T. , Haribabu V. , Venudhar Y. C.
Published: January 2007

Superconducting samples of the composition Bi2‐xPbxCa2Sr2Cu3Oy (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) are prepared by co‐decomposition of metal nitrates. DTA, TGA, density, and porosity studies have been performed on these samples. Characterisation techniques like XRD, SEM, EDXA, d.c. resistance, and a.c. magnetic susceptibility have been employed to study the growth of High‐Tc (HTP) and Low‐Tc (LTP) phases upon lead substitution for bismuth. Results have revealed the growth of HTP with increase in Pb conc. up to x = 0.3. Further increase in Pb appears to results in the deterioration of HTP resulting in the formation of LTP and Ca2PbO4 impurity phase. Transport critical current density (Jc) measurements performed on the samples indicate that Pb doping followed by densification remarkably improves the current carrying capacity of the materials.
Preferred Crystallization of Epitaxially Grown Silicon on Boron‐doped Silicon Substrates
Authors: Stergioudis Georgios
Published: January 2007

The recrystallization of silicon layers on a silicon substrate using X‐ray analysis and X‐ray topography was examined. A preferred crystallization was observed. The crystallites resulting from this process seem to grow along the dislocations consuming part of the elastic energy of the dislocations.
Effect of Melt Convection on the Growth of Nd: YAG Crystal by the Czochralski Method
Authors: Hou Y. , Bai F. , Wang S.
Published: January 2007

The effect of melt convection on the formation of constitutional supercooling defects was studied simply by changing the shape and size of the Ir crucible. The experimental results show that there is a favourable ratio of crucible diameter d to depth h, i.e. d/h is about 1, and a moderate range of the crystal rotating rate must be avoided to grow a quality Nd: YAG crystal.
Surface Coarsening on High‐Tc Superconducting Single Crystals
Authors: Wang Y. S. , Van Der Eerden J. P. , Bennema P. , Schreurs L. W. M. , Wnuk J. , Van Der Linden P.
Published: January 2007

Surface coarsening on high Tc superconducting single crystals is proposed to be due to the effect of impurity adsorption on the collective motion of growth steps. Differential interference contrast microscopy (DICM), scanning tunneling microscopy (STM), and polarized optical microscopy (POM) were used for the surface phenomena observations.
Lattice Vibrations and Interatomic Forces in AIIB2IIIC4VI Defect‐Chalcopyrite Compounds (II). Analysis of Nonpolar Optical Modes
Authors: Neumann H.
Published: January 2007

A simplified version of the Keating model originally derived for defect‐chalcopyrite compounds is extended to include all AIIB2IIIC4VI compounds with ordered arrays of vacancies. It is shown that the trends and frequencies of the nonpolar optical modes of these compounds can be described within this model. Simple scaling laws for the interatomic force constants are proposed and compared with corresponding relations for other binary and ternary compounds with tetrahedral coordination.
Impedance Measurements on Sintered Discs of Sodium Metavanadate
Authors: Saradhi B. V. Bahuguna , Prasad G. , Bhimasankaram T.
Published: January 2007

Impedance measurements of sintered discs of sodium metavanadate (NaVO3) are investigated in the frequency range 10 KHz to 1 MHz and in the temperature region from room temperature (≈ 30 °C) to 450 °C. A.C. conductivity is calculated from the data. D.C. Conductivity in measured in the temperature range 150 to 450 °C. Debye type of relaxation effects are observed in the loss measurements. The activation energy of the dipoles involved in the relaxation is estimated to be 0.76 eV. The activation energy for A.C. conduction in the temperature range 380 to 450 °C is about 0.78 eV. The relaxation phenomenon observed is explained in terms of space charge polarisation due to defects.
Crystal Growth and Elastic Properties of Hopeite, Zn3(PO4) · 4 H2O
Authors: Haussühl S. , Friedrich M.
Published: January 2007

Single crystals of orthorhombic Zn3(PO4)3 · 4 H2O of optical quality with dimensions up to 12 × 10 × 8 mm were grown from aqueous solutions of ZnSO4 and NaH2PO4 by controlled diffusion of NH3 into the solution. The elastic constants cij and the thermoelastic constants Tij = dcij/dT, T temperature, were determined from ultrasonic resonance frequencies of thick plates in the range between 5 and 40 MHz and between 250 and 320 K. In respect to the longitudinal elastic stiffness hopeite behaves quasi isotropically, however, the elastic shear stiffness shows a large anisotropy of about a factor 2.5. Above 260 K the shear stiffness c66 possesses a quite anomalous temperature dependence (T66 > 0). Further, the linear thermal expansion reveals a strong anisotropy (α11 = −3.3, α22 = 3.4, α33 = 33 · 10−6/K).
A Solvent for Liquid‐Phase Layer Growth on BaF2 Substrates
Authors: Trifonova E. P. , Kushev D. B. , Duharska K.
Published: January 2007

Lead diiodide has been proposed as a solvent for liquid‐phase growth of PbTe layers on BaF2 substrates. The contact with pre‐eutectic (PbI2‐PbTe) solutions has resulted in deposition of PbI2 islands of spherical cupola shape. The relatively small contact angle (16–25) indicates heterogeneous nucleation. At certain experimental conditions dense layers of PbI2 have also been prepared. This crystallization is an indirect evidence for good wettability of the BaF2 substrate.
Study of the Concentration Distribution of SiC Vapour in the Crystal Growth Zone
Authors: Lilov S. K. , Yanchev I. Y.
Published: January 2007

In the present work the gas dynamics in the growth zone of SiC crystals is investigated. It is shown that the propagation of SiC vapour from the growth cavity walls towards the lids is effected by diffusion. On this basis the calculation of the concentration distribution of SiC vapour (n), the equilibrium vapour concentration (ns), and the supersaturation \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\alpha {\rm = }\frac{{n - n_{\rm s} }}{{n_{\rm s} }} \cdot {\rm 100\%}} \right) $\end{document} in the crystal growth zone at different radial and axial temperature gradients is carried out by solving the Laplace equation in cylindrical coordinates for a stationary case corresponding to the conditions of crystal growth. The received results are compared with the available experimental data which gives a possibility for explaining some of the observed peculiarities during SiC crystal growth from the vapour phase by the sublimation method.
Mechanical Properties of Copper Films
Authors: Chourasia N. C. , Kalkundri S. B. , Gadgeel V. L.
Published: January 2007

Mechanical properties of vacuum‐deposited copper films have been studied on various well cleaned and polished substrates. The density reaches the bulk value for a film thickness of 4 μm and above. The strain developed during the growth of film was found to be tensile and is dependent on nature of the substrate. The adhesion of film was observed to be thickness — and time of ageing dependent. The results are discussed.
Compressibility in the Orthorhombic Phase of AgInS2 from the X‐ray diffraction data under high pressure
Authors: Orlova N. S. , Turtsevich G. A. , Bodnar I. V.
Published: January 2007

The compressibilities for different crystallographic directions in the orthorhombic modification of the ternary AgInS2 compound were studied as a function of pressure up to 4.5 GPa by the X‐ray poweder diffraction method under high pressure. The anisotropy of compressibility was found to exist and between the principal components of compressibility tensor the relation χc > χa > χb was observed. For the orthorhombic modification the bulk modulus is smaller than that for tetragonal one.
X‐ray Topographic Defects' Contrast on Synthetic Quartz
Authors: Chirilă R. , Csiki Z.
Published: January 2007

In the present study the linear defects in several synthetic quartz have been surveyed by X‐ray topography using Lang method. The grown‐in dislocations produced by layers displacement around holes, precipitates or inclusions are discussed. Each growth zone is described with their own defects pattern and some correlations with the external morphology of the crystal are stated. There are also pointed out the asymmetry of the defects for every growth zone and the specific role in the growth mechanism of the s‐growth zone. In the final part of the work there are outlined the general and the specific conclusions.
Microtopographical Characterization of Vapour‐grown SnS2Single Crystals
Authors: Arora S. K. , Patel D. H. , Agarwal M. K.
Published: January 2007

Thin flakes of tin disulphide single crystals grown using direct vapour transport have been subjected to characterization to unfold their growth mechanism. Two types of spirals. viz. those having opposite orientation present on the same face and those present on the opposite finished faces are significantly discussed.
Ultraviolet Reflectivity of TlSbS2
Authors: Merkel M. , Kleint Ch. , Neumann H. , Horak J.
Published: January 2007

Reflectivity spectra of TlSbS2 single crystals are measured in the photon energy range from 1 to 12 eV. The spectra exhibit 19 structures which are compared with previous measurements and discussed in terms of theoretical band structure calculations. The optical functions are calculated for the photon energy range covered in the experiment.
FT‐IR and Raman Spectra of Ammonium Hydrogen Tartrate and Potassium Hydrogen Tartrate Crystals
Authors: Kolandaivel P. , Selvasekarapandian S.
Published: January 2007

FT‐IR and Raman spectra of ammonium hydrogen tartrate [NH4HC4H4O6] and potassium hydrogen tartrate [KHC4H4O6] have been measured. Vibrational assignments have been made for both the internal and external vibrations. Because of the free rotation of the NH4+ ion, it forms only weak hydrogen bonds with the oxygen atom.
Phase Resolution Method of PA Spectra in Copper(II)‐EDTA Complexes
Authors: Yugeng Zhang , Guiwen Zhao
Published: January 2007

The complexes crystals of Cu(H2EDTA) · H2O and CaCu(EDTA) · 4 H2O were synthesized and their photoacoustic spectra were determined in the region of 300–800 nm at room temperature. A method used to directly monitor both position and strength of the absorption bands of respective electronic states were proposed. With the amplifier and phase spectra all absorption peaks of different electronic states could be distinguished. The PA spectra were also explained by the 3d orbit radial scaling theory. All the d‐d transition absorption peaks calculated are in good agreement with the experimental values. In addition, the non‐radiative relaxation process and the relaxation time of excitation electron were discussed with the PA spectra.
The Phase Relations in the Quasi‐Binary System LiBaF3AlF3. A Search for New Fluoride Laser Hosts
Authors: Al‐Mansour M. , Wallrafen F.
Published: January 2007

In a search for new fluoride laser host materials (esp. with an Al site for Cr3+ doping) the phase relations in the join LiBaF3AlF3 of the ternary concentration diagram LiFBaF2AlF3 were investigated by difference thermal analysis method from 15 samples with different compositions. A new congruently melting compound LiBaAlF6 (Tm = 785 °C) was found. The α‐β‐phase transformation at 671 °C prevents the growth of β‐LiBaAlF6 single crystals from the own melt and the application to laser technology.
Double‐Heterostructure Indium‐Tin Oxide/InGaAsP/AlGaAs Lasers
Authors: Takahashi N. S. , Hunyu Y. , Shibano E. , Mochizuki N. , Kurita S.
Published: January 2007

The fabrication and characterization of double‐heterostructure (DH) laser that utilizes an indium‐tin oxide (Ito) transparent cladding and top contact layer. The first room‐temperature lasing operation has been obtained form ITO/InGaAsP/AlGaAs DH laser diode at threshold current density of 12.1 kA/cm2. The interfacial recombination velocity of ITO/InGaAsP Interface was estimated to be 4.9 × 104 cm/s from a simple model to account for high threshold current, and optical measurements of spontaneous emission and lasing spectra from top stripe window and facet were done.
Thermo‐acoustical Parameters of Some Semiconductors
Authors: Reddy R. R. , Kumar M. Ravi , Rao T. V. R. , Sharma B. K.
Published: January 2007

The thermo‐acoustical parameters of some compound semiconductors are evaluated in terms of the coefficient of thermal expansion, on the assumption that the Moelwyn‐Hughes parameter is the dominant factor. The Moelwyn‐Hughes parameter has been utilised to establish some simple relations between the lattice Grüneisen parameter, Beyer's, non‐linearity parameter, Rao's acoustical parameter, Sharma's thermo‐acoustical parameter, the fractional available volume, the repulsive exponent of intermolecular potential, the Anderson‐Grüneisen parameter and the molecular constant. A relationship between the isothermal, isochoric, and isobaric Grüneisen parameters has also been studied. An estimated parameter Y is found to have values close to 0.11 form which one may infer that the normal modes of vibrations contributing to heat capacities are very small. Sharma's parameter has been found to be approximately constant in the case of semiconductors studied.
Simulation and Experiment in X‐ray Topography and Diffractometry
Authors: Köhler Rolf
Published: January 2007

X‐ray double crystal topography and high resolution diffractometry reveal very small deformations of the crystal lattice. However, this information can be directly obtained from the topographs or diffractometer curves only if certain conditions are fulfilled. Generally a deformation model has to be used, that is compared to the measurements by simulation calculations based on the dynamical diffraction theory. Trial and error allow to adapt the parameters of the model. An example illustrates that with a few parameters an automatic fit is possible.
Crystal Structure of 1‐Phenyl‐3‐Methyl‐5‐Pyrazolone Perchlorate (ES‐1)
Authors: El‐Shora A. I. , Abdeen A. M. , Gaballa G. A.
Published: January 2007

The crystal of ES‐1 belongs to the orthorhombic system, space group Pbca. Unit cell parameters were determined by least squares method and found to be: a = 16.256(8), b = 15.359(8), and c = 9.918(5) Å. The structure was solved by direct methods using the program SHELX86. The refinement was carried out using isotropic thermal parameters then followed by several cycles of anisotropic least squares to a final value of R0 = 0.073 for 1226 observed reflections. The hydrogen atoms were located from a difference Fourier map. Torsion angles calculation showed that rings A and B are planar as expected. All the calculations were carried out on a PC‐Computer at physics department, Tanta University.
Electrical Conductivity of Tetrathiafulvalene‐9‐Dicyanomethylene‐2,4,5,7‐tetranitrofluorene(TTF‐DT4‐NF)
Authors: Salmerón‐Valverde A. , Robles‐Martínez J. G. , Juárez‐Posadas J. , Galindo‐Guzmán A. , Zehe A.
Published: January 2007

We deal with optical properties of TTF‐DT4NF together with electrical conductivity measurements made with rod‐like samples carrying a silver paint contact at both ends. Schottky barrier formation was observed in each case, although strongly modified by tunneling carries across the only thin barriers formed due to a high impurity content of the samples. In the higher voltage range non‐ohmic bulk conductivity behaviour is manifest.
Low‐temperature LPE Overgrowth of InGaAs/InP Mesa Heterostructure
Authors: Follner Procházková , Novotný J.
Published: January 2007

Preparation of planar buried mesa ridge (PBMR) epitaxial wafers suitable for integrated optoelectronic circuits is presented. For this purpose the LPE growth of InP and InGaAsP (λg = 1.3 μm) below 600 °C on nonplanar ridge pattern was realized. Etching of the InGaAsP/InP ridge structure with ridge of 2–2.5 μm was found to be reproducible when HBr:H2O2:H2O etchant was used. The best PBMR epitaxial wafers were obtained via regrowth in multiple‐bin sliding boat by two thin layers of InP using a combination of one‐ and two‐phase growth processes between 600 and 594 °C.
Preparation and Characterization of MBE‐grown Si/CaF2 Heterostructures
Authors: Rossek U. , Mäder M. , Tempel A.
Published: January 2007

Growth and fabrication of silicon‐on‐insulator structures, based on heteroepitaxial growth of insulating films on Si, is an area of research that has rapidly developed in recent years. Thin CaF2 films and Si/CaF2 multilayers were prepared on {111}‐oriented Si substrates by molecular beam epitaxy (MBE) and were investigated by RHEED and RBS. For epitaxial growth the Si substrates were cleaned using the ultraviolet/ozone surface cleaning method which is an effective tool to remove contaminants from the surface by low‐temperature in‐vacuo preheating. The growth of CaF2 on such Si{111} substrates provides epitaxial layers with a high structural perfection. When this layer system, however, is used as a substrate for epitaxial Si growth the Si layers show always twin formation. Si layers without twins could be obtained only after deposition of thin amorphous Si buffer layers at room temperature, immediately followed by Si growth at 700 °C.
Hard Heteroepitaxy on 2° Off‐oriented GaAs (100) Substrates (I). The Occurrence of (100) and (111) Surface Orientations in MBE‐grown PbTe Films
Authors: Sadowski J. , Dynowska E. , Regiński K. , Herman M. A.
Published: January 2007

The MBE growth of PbTe layers on GaAs (100) 2° off‐oriented substrates belongs to hard heteroepitaxy, because the two materials differ strongly in their lattice constants and, in addition, they also exhibit different crystal structures. Consequently, phases with different surface orientations may occur in MBE‐grown PbTe epilayers. Two crystallographic orientations, i.e. (100) and (111), have been found in the PbTe epilayers grown by MBE on these off‐oriented substrates. X‐ray diffraction and reflection high energy electron diffraction (RHEED) measurements applied as post growth characterization techniques allow to identify which orientation is prevailing in films grown at different MBE conditions. It has been shown that the occurrence of the (100) and (111) orientations in MBE‐grown PbTe epilayers depends mainly on the GaAs substrate in situ preheating procedure. At higher preheating temperature and longer preheating time the (111) orientation prevails. This finding is in accordance with the theoretical model of hard heteroepitaxy of CdTe on GaAs (100) substrates by Griesche et al.
On Formation of Corrosion Products in Sanitary Pipes
Authors: Wollmann M. , Jacobi H. , Follner H.
Published: January 2007

In copper pipework, at work for about four years, blue coloured striations or areas, mainly composed of posnjakite (Cu4(OH)6SO4 · H2O), were found (water chemistry (room temperature): pH = 8.1; SO4 = 24 mg/l; Cl = 16 mg/l; O2 = 10 mg/l). Moreover cuprite, tenorite and malachite were detected on the internal surfaces of copper pipeworks. After the pipework had been in operation for five years, an NaHCO3‐dosing apparatus was installed to treat water in all but one branch of the system. In the section with treated water, sulphate formation decreased while malachite formation (Cu2CO3(OH)2) increased. Layer formation can be simulated in electroysis experiments. Normal tap water alone or mixed with bicarbonate is used as an electrolyte.
DSC Transformation Behaviour of a bcc Mg11Sm Phase Prepared by Rapid Solidification
Authors: Budurov Stojan , Zolova Genka
Published: January 2007

The transformation behaviour of the bcc Mg11Sm phase prepared by rapid solidification from the melt has been studied by DSC. The Kissinger and Ozawa equations led to the following activation energies of the first and the second phase transition: E ≈ 130 kJ/mol and E ≈ 194 kJ/mol, respectively. Isothermal Avrami kinetics of the first phase transition starts with an Avrami exponent n ≈ 2,5, dropping down at higher degrees of transformation to n ≈ 1.5. The data obtained have been compared with the parameters of the isothermal Avrami kinetics of decomposition of a rapidly quenched supersaturated MgYb4.87 alloy.
Influence of pH on the Crystal Size Distribution of Mg(OH)2 Prepared by the Hydration of MgO
Authors: Láska M. , Valtýni J. , Fellner P.
Published: January 2007

The effect of pH and temperature of aqueous solution on hydration of MgO in a batch laboratory reactor was investigated. The experiments were carried out at the temperatures of 120 and 140 °C, pH of cool solution was changed from 10 to 13. It was found that even a small amount of added base substance influences remarkably the size of Mg(OH)2 crystals. Increasing of pH of aqueous environment of causes the decrease of the size of crystals. The increase of the temperature increase dimensions (L50) of crystals. This effect is more important at higher alkalinity of the solution.
The Real Structure of Ge Ions‐implanted Si Crystals Subjected to Thermal Annealing
Authors: Auleytner J. , Adamczewska J. , Reginński K.
Published: January 2007

In the experiment an (111) oriented silicon plate was subjected to implantation by 80 keV Ge ions. Then, the thermal annealing of this sample was carried out in a vacuum of 5 · 10−8 Tr. The effectiveness of the annealing has been analyzed by means of X‐ray topography, double crystal X‐ray spectrometry and reflection high energy electron diffraction. The rocking curves in reflection and transmission as well as changes in anomalous absorption coefficient were measured. The results have been compared with effects of pulsed‐laser annealing investigated by AULEYTNER et al. an thermal annealing (PRUSSIN).
Influence of the Substrate Hardness on the Validity of Bückle's Rule
Authors: Berg Gunnar , Grau Peter
Published: January 2007

Generally the substrate hardness of a coated sample influences the measured compound hardness also for small penetration depths. But there exists the empirical rule (Bückle) that for small penetration depths this influence can be neglected. This should be right for values smaller than 1/10 of the film thickness with the limits 1/7 and 1/14. Bückle accentuates the equivalence of the rule for soft films on hard substrates and hard films on soft substrates, respectively.

The possibility is shown that the compound hardness can be estimated from film and substrate hardness by an interpolation formula without any suggestions with respect of the depth dependence of the hardness of the two materials. By means of this formula one can show that the mentioned Bückle rule is not generally valid. Only for soft films on hard substrates one can estimate a noticeably Bückle region useful to measure the film hardness directly for penetration depths up to about 1/10 of the film thickness.
A Mechanism of High‐Tc Superconductivity Relating to Perovskite Crystal Structure
Authors: Wang Y. S. , Bennema P. , Zheng M. N. , Fu C. M. , van der Linden P.
Published: January 2007

A mechanism of high‐Tc superconductivity related to the perovskite crystal structure is proposed by a “phonon attenuation model”, which means that in the perovskite‐like crystal structure, a number of “ordering” vacancies or holes occur due to the non‐stoichiometric structure features. Such a reticular “spongly‐like” structure facilitates lattice thermovibration attenuation perovskite (phonon attenuation) during temperature reduction. This leads to an abrupt drop of the resistivity, owing to the conduction electrons transmitted through the media without collision with irregularities in the lattice due to the lattice thermovibration. This probably is the main reason for high‐Tc superconductivity of the perovskite cuprates.
Electric Field‐Induced Phase Transitions in Electro‐Optic Cell with Dielectrically Negative Chiral Nematic Liquid Crystal
Authors: Pirkl S.
Published: January 2007

Behaviour of a chiral nematic mixture with a negative dielectric anisotropy was studied between two electrodes with homeotropic anchoring in the presence of an a.c. electric field. By changing the sample thicknessdand field strengthEat constant cholesteric pitchp, the phase diagram in the parameter plane (d/p, E) was determined. Usefullness of this diagram for realization of positive contrast dichroic LC displays with nematic‐cholesteric phase change is discussed.
Control of Nucleation in Gel by GNGT — II
Authors: Sivanesan G. , Pandian S. Selvasekara , Gnanam F. D.
Published: January 2007

The Graded Neutral Gel Technique (GNGT) of controlling the nucleation was extended to the gel growth of crystals by a solubility reduction process. Successful and interesting results were obtained in five systems, of the six tried. Attainment of morphological stability, growth around the axial region, and elimination of the growth of pseudo‐structures and salting out effect were the salient features observed.
On Mechanism of Oxide Formation in Electrodeposited Co‐based Films with Columnar Structure
Authors: Tochitskii T. A. , Shadrov V. G. , Boltushkin A. V.
Published: January 2007

An investigation of the Co oxides formation and distribution dependent on preparation conditions during electrodeposition of hcp Co‐based films with perpendicular magnetic anisotropy has been made. It has been shown that the [100] oriented columnar crystallites promote some regularity in impurity distribution and orientation in the film plane, whereas the [001] oriented ones‐ non‐regular distribution. Such a behaviour is associated with the difference in the impurity incorporation for these two cases: preferably crystalline and intergranular, respectively, and atomic bonds saturation, and influence on the mechanical and magnetic properties of the investigated films.
Ferroelectric PbTiO3 Powders and Thin Films Derived from Sol‐Gel Processing
Authors: Cho C. R. , Jang M. S. , Jeong S. Y. , Kim Y. B.
Published: January 2007

Lead titanate powders and thin films were prepared by the sol‐gel process of metal alkoxide solutions and solvents. From DSC measurements, phase transition temperature of crystallized PbTiO3 powders was obtained at about 484 °C. From XRD investigation, it was confirmed that the tetragonal phase of polycrystalline PbTiO3 thin films is formed by coating of concentrated solution on all of the substrates we used after heat treatment above 500 °C.

It was found by SEM and ellipsometric analysis that the thin film coated with 0.25 M concentrated solutions once had an average thickness of about 720 Å. Surfaces of thin films were crack‐free, uniform, and its average grain size investigated by SEM was 0.6–0.8 μm. Band gap energy of PbTiO3 thin film coated on the Al2O3 (2243) substrate was 3.45 eV, which is assumed to be due to the direct band to band transition. Dielectric constant (ϵ) and dielectric loss (tan δ) of PbTiO3 thin film amounted to 60–70 and 0.01–0.02 in the region of 10 kHz ∼ 1 MHz at room temperature, respectively, and transition temperature was 486 °C at 1 MHz. From the hysteresis loop of PbTiO3 thin film, spontaneous polarization of 12 μC/cm2 and coercive filed of 45 kV/cm were obtained.
On Texture Formation at Cold Rolling of Mn‐Cu Alloys
Authors: Demin S. A.
Published: January 2007

The texture formation in quenched γ‐phase Mn‐Cu alloys at cold rolling have been studied. It was found that the final texture in martensitic Mn‐10% Cu alloy consists of nearly equal volume of {001}〈100〉 and {112}〈111〉 texture components. A sharper {101}〈121〉 component in small amounts can be present too. In austenitic Mn‐22% Cu alloy the {112}〈111〉 component is more scattered and weakened, and the strong {101}〈121〉 component has formed. In the Mn‐30% Cu alloy the {001}〈100〉 component is almost absent, {112}〈111〉 is very weak and the {101}〈121〉 texture is dominated.
X‐Ray Studies of Some Europium Compounds at Elevated Temperatures
Authors: Hussain K. A. , Sirdeshmukh D. B.
Published: January 2007

The temperature variation of the lattice constants of europium iron garnet (Eu3Fe5O12), europium sulphide (EuS) and europium fluoride (EuF2) has been studied using an X‐ray powder diffractometer. The lattice constant of Eu3Fe5O12 increases linearly upto 800 °C with an expansion coefficient of 10.4 × 10−6 °C−1. In the case of EuS, the lattice constant increases non‐linearly with temperature. At room temperature the expansion coefficient has a value of 14.3 × 10−6 °C−1. In EuF2 the lattice constant increases non‐linearly upto 140 °C. At higher temperatures, the lattice constant decreases with increasing temperature with a negative expansion coefficient of −29 × 10−6 °C−1 over the range 170–235 °C. The cause of the anomalous behaviour observed in EuF2 is yet to be understood.
Effect of Thermal Treatment and Sweeping on the Electrical Conductivity of Quartz Crystals
Authors: Iliescu B. , Topa V. , Tanase A. T.
Published: January 2007

The effect of thermal treatment and sweeping at different temperatures on the current peaks occurring during the heating‐up phase of the electrodiffusion runs are studied. Arrhenius plots of swept synthetic quartz are discussed.
Doping of GaSb single crystals with volatile elements
Authors: Štěpánek B. , Šestáková V. , Krištofik J.
Published: January 2007

The Czochralski technique without encapsulant in a flowing atmosphere of hydrogen was used for the growth of GaSb single crystals doped with either sulphur or nitrogen. It has been shown that this method is not suitable for the prepartion of GaSb doped with volatile elements because they evaporate during the growth procedure and impair the single crystalline growth. The highest concentration of sulphur in the single crystals has been found to be < 1.2 × 1017 atoms · cm−3. At higher concentrations, GaSb became either polycrystalline or twinned. The growth of N‐doped single crystals was similar to that of S‐doped GaSb.
Highly homogeneous polycrystalline HgTe synthesis under pressure
Authors: Lazarescu M. F. , Manea A. S.
Published: January 2007

A high pressure technique for the direct synthesis of polycrystalline HgTe in quartz ampoules is presented. An excess of mercury as well as a quasi‐static regime of the inert gas pressure at melt temperatures up to 750°C have been used. X‐ray diffraction and SEM confirmed the structural homogeneity of the synthesized material.
Simulation of dopant zone‐leveling in a solid ingot
Authors: Cywiński R. , Damm J. Z. , Poźniak J.
Published: January 2007

Simple simulation procedure permitting to perform accurate calculations of the dopant distribution in an ingot after desired number of passes of the molten zone is presented. The results obtained for various distribution coefficients and various widths of the molten zone are discussed. It is shown that the number of passes indispensable for the dopant concentration leveling drastically decreases with the width of the molten zone even for the most disadvantageous range of the distribution coefficients.
Detection of side‐products on heavy metal cations loaded zeolites by XRD measurements
Authors: Steinike U. , Lutz W. , Wark M. , Jancke K.
Published: January 2007

During the high loading of A, X, and Y zeolites with heavy metal cations by ion‐exchange undesired hydroxides are formed at the crystal surface. The precipitation is caused by the alkaline reaction of the parent sodium modification of zeolites in aqueous solutions and the low solubility product of heavy metal hydroxides. During the calcination of the samples the hydroxides are transformed into oxides. Exemplified by zeolite ZnNaA, a stepwise exchange in strongly diluted salt solutions may hinder the formation of hydroxides/oxides. XRD measurements enable a direct monitoring also of smallest amounts of zinc hydroxide/zinc oxide. The framework adopted ZnO causes a change of the symmetry of the zeolite lattice. The side product does not influence the formation of the new crystalline phases during the calcination of ZnNaA.
Dislocations in synthetic quartz
Authors: Chirilǎ R. , Iliescu B.
Published: January 2007

The present paper is a review of the data about the dislocations in the as‐grown quartz crystal. The work presents some general considerations about dislocations, their origins and causes, methods of their observation and techniques to reduce the dislocations density. It is also shown a method to obtain a new shape crystal used in the positive X‐seeds preparation.
Vertical Bridgman growth and optical properties of doped Bi12SiO20 crystals
Authors: Xuewu Xu , Jingying Liao , Bingfu Shen , Peifa Shao , Chongfan He
Published: January 2007

The core‐free BSO crystals with high optical quality, doped with NiO, Sb2O3, V2O5, Nb2O5, Ta2O5, and P2O5, have been grown by the vertical Bridgman (VB) method for the first time. The “interface” segregation coefficients of the above‐mentioned dopants in BSO with values of 0.014, 0.162, 0.704, 0.039, 0.077, and 0.976, respectively, have been approximately evaluated according to the diffusive solute transport regime with the assumption of negligible natural convection in the melt. The transmission spectra of various doped BSO crystals have been measured in the range from 300 to 700 nm. A blue shift of the transmission edge in Ni‐, Sb‐, and P‐doped BSO and a red shift in Nb‐ and V‐doped BSO have been found as compared to undoped BSO. The modification in the absorption amplitude implies that the photorefractive performances of BSO crystals may be improved through doping.
The emission and structure of a new laser crystal Nd3+: NaY(WO4)2
Authors: Yizong He , Guofu Wang , Xiaoying Huang , Zundu Luo
Published: January 2007

A new laser Nd3+ : NaY(WO4)2 crystal rod of Φ 2.5 × 5 mm was pumped by a xenon flash lamp, and a 1.06 μm laser output was for the first time obtained in our laboratory, which has a threshold lower than 1 J. The crystal structure of NaY(WO4)2 was determined. The crystal is tetragonal, with the space group 141/a, a = 5.205(2) Å, c = 11.251(3) Å, V = 304.8(2) Å3, Z = 2, Dcalc = 6.62 g/cm3, Dobs = 6.51 g/cm3.
EPR study of divalent manganese in northupite single crystal
Authors: Eftaxias K. , Vassilikou‐Dova A. B.
Published: January 2007

EPR spectra of Mn2+ in northupite single crystals were measured at X‐band and room temperature. Only one isotropic sextet is recorded for all orientations. The hyperfine splitting constant of 81 · 10−4 cm−1 is in the expected range for Mn2+ in six‐fold coordination. The very small zero field splitting gives a strong evidence that the occupied site by Mn‐ion is the Mg‐site in consistence with the preference of Mn2+ for such a substitution.
Infrared lattice vibrations of PbGa2S4
Authors: Neumann H. , Sobotta H. , Syrbu N. N. , Golovei V. M.
Published: January 2007

Infrared reflectivity spectra of PbGa2S4 single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm−1 for the polarization directions E ∥ c and E ∥ b. The frequencies of 13 B1u modes and 11 B2u modes are derived from the spectra. The results are compared with previous studies and with lattice vibration data of ternary chalcopyrite and defect‐chalcopyrite compounds.
Growth of dysprosium garnet single crystals with spiral shape using Czochralski technique
Authors: Kimura H. , Numazawa T. , Sato M. , Maeda H.
Published: January 2007

The growth conditions of dysprosium garnets single crystals, to obtain a long and good spiral shape crystal, have been investigated using the conventional Czochralski technique along the [111] pulling direction. The good spiral shape of Dy3Ga5O12 single crystal with 40 mm in length is grown with its spiral pitch and spiral diameter of 20 mm and 15 mm, respectively.
Temperature dependence of grain growth in zone‐refined tin containing large additions of zinc in solid solution
Authors: Fawzy A. , Youssef S. B. , Beshai M. H. N. , Saad G.
Published: January 2007

Grain growth in zone‐refined tin containing high concentrations > 0.05 < 0.40 wt% Zn in solid solution have been investigated in the temperature range 70–160°C. It has been found that increasing the zinc content by a factor of 8 decreased the rate of grain growth by ∼ 30% at all annealing temperatures, and this was attributed to small variations of grain boundary mobility. In addition, the increase of annealing temperature from 70 to 160°C resulted in the increase of grain growth by a factor of ∼ 50 at any given concentration, which shows that the rate of grain growth is not strongly influenced by increasing the zinc concentration. The energy activating the growth process was calculated for all concentrations investigated and had a nearly constant value of ∼ 1 eV. An empirical formula was proposed relating the rate of grain growth and the solute concentration.
Free space crystallography and the volume term of Gibbs energy in heptagon patterns
Authors: Leuschner D. , Leuschner Chr. , Leuschner C.
Published: January 2007

Gaps or free space are studied in heptagon patterns. Geometrical features of 2‐D nets are investigated. The volume terms of Gibbs energy in corresponding 3‐D lattices is estimated. The importance of the research of gaps and space filling is confirmed by the study of the FSCSC (free space crystallography of strange crystals) row of three heptagon patterns with the interesting number (per unit cell) sequences (heptagons: 4, 6, 8; gaps: 2, 3, 4) represented here.
X‐ray crystal structure analysis of parthenin–A sesquiterpene lactone
Authors: Gupta Vivek K. , Goswami K. N. , Bhutani K. K.
Published: January 2007

The crystal structure of parthenin has been determined by X‐ray structure analysis. The compound crystallizes in the tetragonal space group P41 with cell parameters a = b = 6.8677(2), c = 28.6851(4) Å. The structure has been solved by direct methods and refined to R = 0.039. The seven‐membered ring assumes a chair conformation while the two five‐membered rings have envelope shapes. The A/B and B/C junctions are trans. Molecules are held together by hydrogen bonds.
Influence of carbon contamination on etched GaSb substrate on the quality of MBE‐GaSb film and electrical transport through the film and the substrate
Authors: Kodama M.
Published: January 2007

Undoped MBE‐GaSb films were grown on undoped GaSb (100) substrates and the influence of carbon contamination on the etched GaSb substrate on the grown film were investigated. It was found that carbon contamination of the etched GaSb substrate was dependent on the chemical treatment method and produced stacking faults in the subsequent MBE growth of the GaSb film. Carbon contamination on the etched GaSb substrate degraded the quality of the GaSb film and affected ohmic characteristics between the film and the substrate. Substrate surface free of carbon contamination and thereby exhibitting no influence on the electrical transport through the film and the substrate could be reproducibly obtained by performing an oxide etch‐off chemical treatment on the GaSb substrate.
Measurement of supersaturation
Authors: Nývlt J. , Karel M. , Písařík S.
Published: January 2007

The supersaturation of aqueous solutions of potash alum during a batch crystallization experiment has been determined by means of conductometry and refractometry. The results of both of the methods can be compared satisfactorily, but under the given conditions of home‐made equipment the refractometric determination seems to be more reliable.
Influence of proton implantation on the properties of CuInSe2single crystals (II)
Authors: Yakushev M. V. , Neumann H. , Tomlinson R. D. , Rimmer P. , Lippold G.
Published: January 2007

Copper deficient p‐type conducting CuInSe2single crystals were implanted with 40 keV protons in the fluence range from 2.5 · 1014to 1.5 · 1016cm−2. Over the whole fluence range the implanted layers were n‐type conducting which is ascribed to passivation of the acceptors due to copper vacancies and formation of donors by hydrogen atoms located at interstitial positions. The thermal stability of the conductivity changes due to proton implantation is limited to temperatures below 100 °C.
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

For 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

Single 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

Optical 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

The 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

It 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

Superthin 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

Some 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

The 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

The 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

Infrared 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

This 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.