bluuebunny/crossref_metadata_2025_split huggingface dataset:
Paramagnetic defects in the mineral hauyne
Authors: Vassilikou‐Dova A. B. , Lehmann Gerhard 
Published: January 2007

AbstractIn blue crystals of hauyne from two localities two broad signals due to Fe3+, a hole center of tetragonal site symmetry and an isotropic signal from an electron center were detected by electron paramagnetic resonance (EPR). According to its site symmetry the hole center is tentatively assigned to a [MgO4/2]0 species on an Al site with the unpaired electron delocalized over the oxygens. The site symmetry does not change with cooling to 20 K. The large linewidths of the signals from Fe3+ are interpreted as a result of the non‐stoichiometry and high static disorder and some dipolar broadening. The linewidths of the other EPR signals are also larger than for corresponding centers in the isotypic sodalite. The cause of the blue colour is briefly discussed.
Effect of structure on low temperature plasticity and magnetic properties of ageing PbSb alloys belowTc
Authors: Fomenko V. S. , Isaev N. V. , Pustovalov V. V. 
Published: January 2007

AbstractIt was carried out comparative structural, magnetic and mechanical studies of single crystals of Pb—Sb alloys with 0.5–5 at.% Sb, which are II type superconductors. The structure was studied by X‐ray diffractometry, small‐angle X‐ray scattering, microhardness and resistometry methods. It was determined the total volume fraction and the precipitate size. The second critical fieldHc2and the magnetic flux trapping measured at 4.2 K are determined by the solid matrix concentration and the precipitate volume fraction respectively. Plasticity of Pb—Sb crystals was investigated by tension tests at 4.2 K. The dependence of the change of the flow stress, Δτsn, at superconducting transition on ageing time and antimony concentration was obtained.
Growth and microstructural studies of some indium chalcopyrite semiconductors
Authors: Balakrishnan K. , Vengatesan B. , Kanniah N. , Ramasamy P. 
Published: January 2007

AbstractSingle crystals of ternary chalcopyrite semiconductors such as CuInS2, CuInSe2, CuInTe2, and CuInSSe, a pseudo‐ternary semiconductor, have been grown by Chemical Vapour Transport (CVT) technique using iodine as the transporting agent. Microstructural analysis was carried out with the help of Scanning Electron Microscope (SEM) and optical microscope for the grown single crystals.
Calculations of homogeneous region in Ga1−xAlxAs and GaAs1−xPx ternary solid solutions
Authors: Ivashchenko A. I. , Kopanskaya F. Ya. , Tarchenko V. P. 
Published: January 2007

AbstractTernary solid solutions of AIIIBV compounds are considered as pseudobinary A(x)IIIB(x)v compounds, where the behaviour of A(x)III and B(x)v pseudoatoms is quite similar to AIII and Bv atoms in a binary AIIIBv crystal. Weak dependence of point defect contribution into Gibb's energy of AIIIBv crystal on its defect nature, random character of ternary solid solutions of AIIIBv compounds allow to use already for binary compounds developed formalism in the determination of component thermodynamic potentials of solid solution. Basing on literature data for the equilibrium solidus of AlAs the approximation for the temperature dependence of thermodynamic potential of an AB quasimolecule in AIIIBv crystal is revised. This result together with the well‐known parameters for the equilibrium liquidus in Ga–P, Ga–As, and Al–As systems were used for calculations of the nonstoichiometric factor at the boundary of a homogeneous region in Ga1−xAlxAs and GaAs1−xPx ternary solid solutions. The results are compared with the known literature data.
Dislocation density in heteroepitaxial indium arsenide layers
Authors: Trifonova E. P. , Hitova L. 
Published: January 2007

AbstractIn As layers have been grown by CVD on (111)B‐oriented GaAs substrates. The dislocation density (ND) distribution through the layer thickness has been studied. ND is dependent on the mole fraction of AsCl3 in the gaseous phase and, consequently, on the current carriers concentration. This results in the supposition that the decreasing of ND in the layers after a “critical” thickness is due to the “pinning” of dislocations at impurity atoms which form stronger bonds with the host In or As atoms than the bond In–As, an effect which is known for bulk GaAs and InP crystals.
Crystal growth in gel: Investigation of nucleation processes
Authors: Cipanov A. V. , Goshka L. L. , Ruzov V. P. 
Published: January 2007

AbstractThe experimental and theoretical investigations of the nucleation processes of the calcium tartrate crystals in gel are presented in this paper. It has been shown experimentally that the changing of the acidity of the crystallogenetic media strongly influences the depth of the first crystals arising in gel, as well as on the crystals number and the mean mass of one crystal. The acidity changing was done by proton introduction into the gel formed by means of the additional solution (impregnation) or by means of the creation of proper acidity of maternal calcium chloride solution.The theoretical description of this phenomena needs the assumption of the equivalence condition. The equivalence means that the concentration of crystal‐forming reagents can't differ very much.
Growth and characterization of mercurous chloride single crystals
Authors: Baskar K. , Gobinathan R. 
Published: January 2007

AbstractMercurous chloride was purified by repeated sublimation using multichamber distillation column. Single crystals were grown by Physical Vapour Transport technique. During the process of purification of the material, very interesting habit modifications like dendrites and needles were observed. Vickers hardness tests were carried out on the (110) plane of the crystal for different orientations of the indentor. The shape of the impressions for different orientations of the indentor reveals the non‐cubic structure of the plane. No structural phase transition in mercurous chloride was observed in calorimetry and optical studies.
Study of surface morphology of vapour‐grown HgI2 platelets
Authors: Szurgot M. , Laskowski J. 
Published: January 2007

AbstractFresh and old as‐grown {001} surfaces of α‐HgI2 platelets were studied by optical microscopy. The presence of growth hillocks and the high value of the surface entropy factor are proofs of the spiral growth of platelets. In air surfaces became gradually dull. Consequently, the final micromorphology of HgI2 is the result of both growth (primary) and post‐growth (secondary) processes. For the revelation of defects a new, reliable etchant was used.
The influence of etching conditions on surface contamination during silicon etching in CF4 plasma
Authors: Glück B. 
Published: January 2007

AbstractThe dependence of blanked‐etched silicon surface quality on the etch parameters and mask material was studied.First it was tried to find such etch conditions, where the silicon surface keeps clean. It was found that etching in RIE‐mode yields better surfaces than in PE‐mode. There was no noticeable influence by variation the oxygen content in the CF4/O2‐etch gas mixture and the total gas flow. If the generator current was raised, the edge zone of the wafer, where the surface is contaminated, becomes greater.Second it is shown that the presence of aluminium as mask material makes worse the surface quality. This effect is stronger during etching in the RIE‐mode than in the PE‐mode.
Optical absorption and photoelectric properties of Ga2In4S9 single crystals
Authors: Moldovyan N. A. , Chebotaru V. Z. 
Published: January 2007

AbstractPresented in this paper are the results obtained from the investigation of absorption edge and photoconductivity of layered Ga2In4S9 single crystals as well as from the investigation of the photovoltaic effect in Pt—Ga2In4S9 surface‐barrier structures. We determined the magnitude of the direct band gap to be Eg = 2.72 eV and the position of the sensitizing centres to be ≈︁0.15 eV above the valence band top. In the regions of the photon energies smaller than Eg the absorption band edge is described by an exponential dependence with a temperature independent slope.
Growth of CdBr2 crystals by zone‐melting and study of their growth features
Authors: Shukla Nutan , Trigunayat G. C. 
Published: January 2007

AbstractA detailed surface microtopographic study has been carried out on the (0001) faces of melt‐grown CdBr2 single crystals. Mainly the growth of the crystals takes place by continuous solidification at the solid‐liquid interface. Rarely, the growth occurs by two‐dimensional nucleation and still more rarely by spiral mechanism. Most spirals are seen to be polygonized such that the polygonization extends right upto the centres of the spirals.
Purification, growth and ESR studies of sodium nitrate
Authors: Phor J. S. , Chaudhary S. K. , Maken S. 
Published: January 2007

AbstractSingle crystals of sodium nitrate have been purified and grown using zone‐refining system fabricated in our laboratory. Laue photographs were employed to check the crystallinity. X‐ray irradiated crystals have been studied by electron spin resonance.
Crystallization of glaserite from aqueous solutions
Authors: Mazzarotta B. 
Published: January 2007

AbstractCrystallization of glaserite (double salt of potassium and sodium sulphate) from aqueous solutions was studied by determining solubility, metastable zone width, growth and dissolution kinetics. Solubility measurements confirmed the presence of a large range of mother liquor compositions from which the precipitation of glaserite at about 73 – 76 wt% K2SO4 is obtained: inside this region the solubility lines resulted curvilinear. The metastability zone is quite large, ranging from 14 to 23 °C, and mainly increases by increasing the Na2SO4 content in the mother liquor. The growth rate of glaserite is second order, slightly size dependent and primarily controlled by diffusion as for K2SO4 but both growth and dissolution constants are quite lower than those for K2SO4.
Stabilizing effect of non‐framework AL on the structure of dealuminated y zeolites under hydrothermal conditions
Authors: Lutz W. 
Published: January 2007

AbstractWith the dealumination of Y‐type zeolites a modification of catalytic properties as well as a ultrastabilization is attained. With increasing Si/Al ratio the hydrothermal stability should decrease. However, the non‐framework aluminium, containing as amorphous aluminosilicate protects the modified framework against the attack of water.
The influence of different acceptor coactivators on the luminescent properties of CaS: Ce polycrystals
Authors: Bushtruk I. Ya. , Demishev S. V. , Gruzintsev A. N. 
Published: January 2007

AbstractThe influence of coactivators, namely, alkali metals, on the luminance, spectral characteristics and defect composition (by thermoluminescence curves) of green luminophor CaS:Ce obtained by solid phase synthesis, is considered. The use of sodium and potassium is shown to increase the efficiency of cathode luminiscence from 8.5% to 20% and 15%, respectively. This is due to the effect of self‐compensation of the activator (Ce) and coactivator impurities changing the amount of calcium sulfate intrinsic defects. Studies have been made of the thin structure of the luminophor spectrum at 4 K.
The d‐d transition spectrum and Cu(II)‐N bonds of [Cu(2,2′‐bipyridine)2 (saccharin)] (saccharin) · 3 H2O
Authors: Jianmin Li , Yugeng Zhang , Jifa Fan 
Published: January 2007

AbstractFollowing a recent upsurge of interest in saccharin complexes system, we have synthesized several saccharin mixed ligand complexes and attempt to discussed them. In this work, the d‐d transition spectrum of the title compound crystal have been determined and it is explained with scaling radial theory of non‐free ions which was proposed by our laboratory. However, the absorption position of d‐d transitions of the title compound are at 10474, 12435, 13814, 15627 cm−1. With data in the work of Brown and Shannon, Cu(II)‐N bonds of the title compound are discussed and it shows that the coordination ability of saccharin in to copper(II) ion is weaker than that of 2,2′‐bipyridine, but more stronger than that of a water molecule.
On the morphological stability of cubic symmetry class crystals (KBr) growing from aqueous solutions
Authors: Staynova M. I. , Nanev ChR. N. 
Published: January 2007

AbstractMorphological stability is a complex problem, the clarification of which requires the simultaneous consideration of the natural transport of matter by diffusion and the surface incorporation kinetics, hence the distribution of concentration around the growing crystal (Seeger; Cahn; Chernov). In the present paper the instability of KBr single crystals due to the appearance of depressions on their faces during growth from aqueous solutions has been related with the actual concentration distribution on their surfaces and the directly measured growth rates.
Nucleation velocity of NaPO3 melts
Authors: Grantscharova E. , Gutzow I. 
Published: January 2007

AbstractThe time τ for visible crystallization of NaPO3 melts is measured in the whole range of undercoolings from the melting temperature Tm to the temperature of vitrification Tg. It is shown that the time τ, needed for the appearance of a visible crystallization at high supersaturations is determined by the linear growth rate, whereas the rate of heterogeneous nucleation is the main factor, determining the experimentally measured time τ at low supersaturations. The specific surface energy σ at the melt‐crystal interface is calculated from the data on nucleation velocity in the vicinity of Tm and the temperature dependences of both heterogeneous and homogeneous nucleation velocity for NaPO3 melts are constructed. It is concluded that at normal cooling rates only nucleation, initiated by active crystallized cores could be observed for NaPO3.
Growth and characteristics of HgGaInS4 single crystals
Authors: Moldovyan N. A. , Chebotaru V. Z. 
Published: January 2007

AbstractSingle crystals of the HgGaInS4 layered compound were grown by the iodine transport technique. Results of their optical, photoelectric, and radiative properties' study are presented. The band gap and the binding energy of holes on the sensitizing centres were determined to be Eg = 2.41 eV and Ea = 0.2 eV, respectively. A presence of quasi‐continuously distributed states was stated which are responsible for the exponential segment of the absorption edge and which take part in the radiative recombination.
On the preparation and sintering behaviour of barium titanate
Authors: Pfaff G. , Feltz A. 
Published: January 2007

AbstractThe present contribution reports on the preparation of BaTiO3 powders in various ways including the characterization and the sintering behaviour. The powders were synthesized by using precursors like BaTiO(C2O4)2 · 4 H2O and BaTiO2(O2) · 3 H2O, or by an alcoholate/hydroxide method, by a successive precipitation from solutions with following thermal treatment, or by the conventional route from BaCO3 and TiO2. The thermal decomposition of the precursors to BaTiO3 is described. The different sintering behaviour of BaTiO3 compacts is the consequence of granulometric properties and of their content of impurities. Possible sintering mechanisms are discussed.
On the thermal behaviour of molecular beam effusion sources
Authors: Müller B. , Wolf B. , Zehe A. 
Published: January 2007

AbstractMolecular beam epitaxy (MBE) takes advantage of crucibles indirectly heated by an electric resistance heater. These thermal sources can be used to evaporate a great variety of materials. A precise control of the evaporation rate, however, requires a temperature stability of about 1‰. Therefore, a detailed knowledge on the thermal behaviour of the source is indispensible.It is intended to present models describing the response of the source temperature to a step change in heating power and compare the results by experimental data.
Microstructure optical and electrical studies of cadmium selenide thin films
Authors: Mahmoud S. , Eid A. H. 
Published: January 2007

AbstractNucleation and growth of cadmium selenide thin films are of considerable interest because of their direct effect on the optical and electrical properties of this material. Vacuum‐deposited layers on amorphous and crystalline substrates showed a polycrystalline structure. The layers were deposited at a pressure of 10−4 Pa, with two deposition rates of 12 nm/s and 15 nm/s. The electrical resistivity and the optical absorption were studied for a group of layers on quartz substrate. As well the morphology and the microstructure were investigated by X‐ray and electron microscopy. Few activation energies were estimated from the optical absorbance and thermo‐resistance.
Switching effect with memory in thallium sulfide single crystals
Authors: Nagat A. T. , Hussein S. A. , Gameel Y. H. , Gamal G. A. 
Published: January 2007

AbstractThallium monosulfide single crystals have been grown and thin platelet specimens were prepared. The switching characteristics of TIS were studied in detail. Switching effect with memory was observed and reported for the first time. The influence of different variables such as temperature, light illumination, and sample thickness on the switching behaviour is considered. The obtained results are discussed.
“Crystallization E.M.F.” Investigation in the lithium niobate pulling process from the melt
Authors: Aleksandrovskii A. L. , Shumov D. P. 
Published: January 2007

AbstractE.M.F. in the lithium niobate crystal‐melt system as a function of pulling and rotation rates, crystal diameter and orientation was determined. Total E.M.F. is a sum of thermo‐E.M.F. and “crystallization E.M.F.” Δφ. The logarithmic approximation Δφ = Δφ0 In (1 + /v0), where v is a growth rate, Δφ0 = 3.9 mV, v0 = 1.9 mm/h is adequate. The Δφ magnitude is independent within the experimental error on the rotation rate and crystal orientation, whereas it is slightly increasing along with the diameter increase. Some existing models of electric phenomena accompanying crystal growth are discussed and a new model based on charge carrier injection into solid during growth is proposed.
Growth and characterisation of Na3Sb2F9 single crystals
Authors: Benet Charles J. , Sivakumar K. , Gnanam F. D. 
Published: January 2007

AbstractOptically clear single crystals of Na3Sb2F9 have been grown from solution by slow evaporation technique at constant temperature. Crystals of sizes upto 30 × 8 × 8 mm have been grown in a period of three months. Vickers microhardness measurements have been carried out on these crystals. Attempts have also been made to understand the nature of the cracks developed around the microindentation. Single crystal X‐ray diffraction studies have been carried out and cell parameters are determined.
Crystal structure investigation of [Mn(3‐CH3C5H4N)2(N3)2(H2O)2]
Authors: Mautner F. A. , Goher M. A. S. 
Published: January 2007

AbstractThe crystal structure of the title compound has been determined by single crystal X‐ray diffraction methods. [Mn(3‐CH3C5H4N)2(N3)2(H2O)2] crystallizes in the space group P 1 with a = 7.444(2) Å, b = 7.691(2) Å, c = 8.926(3) Å, α = 99.82(3)°, β = 108.80(2)°, γ = 114.99(2)° and Z = 1. Least squares refinement gave a R value of Rw = 0.046 for 1414 observed reflections.The manganese atom in the title complex is octahedrally coordinated by two oxygen atoms of the water molecules and four nitrogen atoms; two N‐atoms are the end atoms of azide groups and the other two nitrogen atoms belong to the 3‐methylpyridine molecules. The polyhedra are linked via hydrogen bonds between the water molecules and the azide groups.
The effect of local centers on conduction and luminescence of boron nitride
Authors: Galanov Yu. I. , Konusov F. V. , Lopatin V. V. 
Published: January 2007

AbstractEnergetic and kinetic characteristics of charge carrier trapping and recombination centres in graphite‐like boron nitride produced by gas‐phase deposition are discussed. Local levels in X‐ray excited PBN are studied using the method of thermally activated spectroscopy of luminescence and conduction, and their position in the band gap is determined from the temperature dependences of the diffusive current and depolarization current. Acceptor and donor level models for different PBN are developed. Their influence on conduction and on luminescence is determined. The scheme of hole‐electron transitions by luminescence is suggested. The carbon influence on the nature of the defects creating local levels is discussed.
Kinetics of growth of calcite crystals in presence of ammonium ions
Authors: Söhnel O. , Handlířová M. , Macenauer J. 
Published: January 2007

AbstractThe growth of calcite crystals from an aqueous supersaturated solution of initial concentration 0.15 mol m−3 containing 10 mol m−3 of (NH4)2CO3 has been studied at 298 K. The progress of growth has been followed through determining the composition of the solution by chemical analysis. The crystal growth is controlled by the surface reaction mechanism and satisfies a kinetic equation of the second order with the rate constant 3.7 × 10−6 m4 mol−1 s−1 that is independent on the surface area of the present solid. NH4+ ions do not change the crystal growth mechanism but decrease the growth rate of calcite crystals.
Growth of KDP crystals by splicing “parallel”‐seed in aqueous solution and its mechanism
Authors: Feng Pan , Jinkui Liang , Genbo Su , Qinglan Zhao , Youping He , Yisen Huang 
Published: January 2007

AbstractGrowth of the habit of a single seed and the special growth of splicing “parallel” seeds were investigated and compared with. Chemical etching and X‐ray topography were used to characterize spliced KDP crystals. The kinetic data in different growth stages were measured. It is concluded that secondary capping is the most important stage in the splicing parallel‐seed growth, and that the subgrain boundaries emitted from the secondary cap are parallel to or overlap with the splicing boundary and stretch to the prismatic surface about 45° to the z‐axis, and that above the twin‐crystal regions with subgrain boundaries the real monocrystalline region appears. The growth kinetics of the subgrain boundary approximately corresponds to the growth mechanism of single‐spiral dislocation.
Solidification behaviour of eutectic and monotectic alloys: Succinonitrile ‐ acenaphthene system
Authors: Rai U. S. , Shekhar H. 
Published: January 2007

AbstractThe phase diagram of succinonitrile‐acenaphthene system, determined by the thaw‐melt method, shows the formation of a eutectic at 0.99 mole fraction of succinonitrile and a monotectic at 0.35 mole fraction of succinonitrile with a large miscibility gap. The linear velocity of crystallization (v) of the pure components, eutectic and monotectic, studied at different undercooling (ΔT) by measuring the rate of movement of the growth front in a capillary, suggests that crystallization data obey the equation: v = u(ΔT)n where u and n are constants depending on the nature of solidification of the compounds. While the microstructural investigation of eutectic shows broken lamellar and eutectic dendrite‐type morphologies that of monotectic exhibits fibrous and broken fibrous‐type microstructures depending on the rate of solidification.
Dependence of electrical conductivity and activation energy of lithiumzinc ferrites on sintering temperature and porosity
Authors: Ravinder D. , Seshagiri Rao T. , Muley V. N. , Reddy K. B. 
Published: January 2007

AbstractThe electrical conductivity (σ) and thermoelectric power (Q) of polycrystalline lithiumzinc ferrites sintered at 1200 and 1300 °C was investigated as a function of temperature. The porosity and activation energy were calculated. It was found that the electrical conductivity is progressively increasing with increase of sintering temperature while the porosity and activation energy decrease continuously. The carrier concentration (n) and mobility (μ) of charge carriers has been discussed as a function of sintering temperature and temperature, respectively.