bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal behaviour of natural heulandite crystals
Authors: Kumar P. K. Jeethendra , Rao P. Mohan , Setty D. L. R. 
Published: January 2007

AbstractThermal behaviour of natural heulandite crystals collected from Pashan area near Poona, India, is studied by employing static weight loss method (SWL), X‐ray diffraction, infrared spectroscopy, TG and DTA. The combination of these techniques provide better understanding of the structural modifications that occur in heulandite during thermal treatment. It is observed that heulandite structure is transformed from its ‘A’ phase to heulandite ‘B’ phase between 250–400 °C, and forms another intermediate metastable phase heulandite ‘C’ before the structure starts degrading above 500 °C.
Contribution to the determination of the entropy production for steady state eutectic growth
Authors: Wolczyński Waldemar 
Published: January 2007

AbstractIn order to find a generalized entropy production for steady‐state eutectic growth the entropy production per unit time and volume is to be determined. A relationship which expresses the entropy production per unit time and volume as a function of KRUPKOWSKI's equations is shown. It is in a qualitative accuracy with LESOULT‐TURPIN's theory. The above quantity is to be integrated over a distinguished volume of the unidirectionally solidified eutectic structure. A correlation between this volume and entropy production is discussed.
Dislocation internal friction and temperature dependence of yield stress in high‐purity molybdenum single crystals
Authors: Lebedev A. B. , Kardashev B. K. , Hofmann U. , Kaufmann H.‐J. , Schulze D. 
Published: January 2007

AbstractHigh purity molybdenum single crystals (residual resistivity ratio ≈ 6 · 104) were studied by means of computer‐controlled internal friction technique at frequencies of about 100 kHz in the temperature range 6 to 300 K. The amplitude dependences of decrement were measured within the vibrational strain amplitude 10−7 to 10−4. It was established that the temperature dependence of ultrasonic amplitude providing a constant level of reversible dislocation deformation coincides well in relative units with the temperature dependence of the critical resolved shear stress at 20 to 180 K.
Some observations on melt‐grown cadmium iodide crystals
Authors: Chaudhary S. K. , Mohan D. , Trigunayat G. C. 
Published: January 2007

AbstractSingle crystals of richly polytypic compound cadmium iodide have been grown using a zone‐refining system. The frequent appearance of cracks in the grown crystals has been attributed to the thermal stresses and the presence of impurities. Structure of all the crystals has been found to be of the type 4H.
Evaluation of experimental parameters influencing the growth of large crystals of NaX zeolite
Authors: Kornatowski J. , Finger G. , Schmitz W. 
Published: January 2007

AbstractFollowing the Charnell's procedure, the influence of materials, methods of preparation and changes in composition of the gel on the process of NaX zeolite crystallization have been investigated in order to find conditions providing both the growth of crystals as large as possible and also good reproducibility of the result. The experimental conditions used are detailed described.
Formation of dislocation etch grooves in potassium bichromate crystals
Authors: Szurgot M. 
Published: January 2007

AbstractThe formation of etch patterns on dislocations in potassium bichromate (KBC) crystals has been studied. It was found that, depending on the relative position of a dislocation line with respect to the etching plane, either a groove or a groove associated with a pit or a pit alone are formed. A dislocation lying in the etching plane or not much inclined from it gives a groove or an array of etch pits. An inclined dislocation gives a groove connected with an eccentric pit and a normal one gives a centric pit. A dislocation to be revealed as an etch groove has to lie sufficiently close (<100 μ) to the observation plane.
Crystal and molecular structure of 17α‐acetoxy‐21‐hydroxy‐1,4‐pregnadiene‐3,20‐dione
Authors: Scharfenberg‐Pfeiffer D. , Megges R. , Bohl M. , Simon K. , Stopsack H. 
Published: January 2007

AbstractThe title compound 17α‐acetoxy‐21‐hydroxy‐1,4‐pregnadiene‐3,20‐dione crystallizes in the orthorhombic space group P 212121 with four molecules in the unit cell and the lattice parameters a = 10.950, b = 11.857, c = 15.634 Å. The crystal structure was determined by direct methods and refined by full matrix least squares calculations up to the discrepancy factor R = 0.050.Die Titelverbindung 17α‐Acetoxy‐21‐hydroxy‐1,4‐pregnadien‐3,20‐dion kristallisiert in der orthorhombischen Raumgruppe P 212121 mit vier Molekülen in der Elementarzelle und den Gitterkonstanten a = 10,950, b = 11,857, c = 15,634 Å. Die Kristallstruktur wurde mit direkten Methoden bestimmt und mit der Methode der kleinsten Quadrate bis zu einem R‐Wert von 0,050 verfeinert.
The crystal and molecular structure of 5α,8α‐epidioxyergosta‐6,22‐dien‐3β‐acetate
Authors: Kutschabsky L. , Lindequist U. , Kretschmer R.‐G. 
Published: January 2007

AbstractFrom the mushroom species Tricholoma populinum LANGE which shows interesting pharmaceutical effects the steroid 5α,8α‐epidioxyergosta‐6,22‐dien‐3β‐ol has been isolated. The acetate of this compound crystallizes in the monoclinic space group P 21 with two molecules in the unit cell of dimensions a = 19.788, b = 7.241, c = 9.914 Å, β = 103,97°. The final R‐value is 0.079 for 1082 reflections.
Effect of heat treatment on the optical absorption of tin diselenide thin films
Authors: Bhatt V. P. , Gireesan K. , Desai C. F. 
Published: January 2007

AbstractOptical absorption measurements were made on tin diselenide thin films grown on glass substrates by thermal evaporation of stoichiometric bulk compound. In the as‐deposited films, optical absorption was dominated by an indirect transition at lower photon energies with a band gap of 1.4 eV. The direct allowed transition with a band gap of 1.62 eV was predominant at higher energies. Annealing the film at elevated temperatures resulted in the decrease of both the direct and indirect transition band gaps.
Kinetic investigations within the transition region from polyhedral to skeletal growth mode (II). Growth kinetics of the edge of the basal face of zinc single crystals under diffusion conditions
Authors: Iwanov D. 
Published: January 2007

AbstractThe growth kinetics of the edge of the basal face of zinc single crystals grown from a vapour phase under diffusion controlled conditions has been investigated. The growth of the basal edge with time at constant temperature and supersaturation and argon pressures between 5 and 250 Torr or in vacuum 1 × 10−6 Torr has been plotted. It is established that the length a of the edge of the {0001} face is changed with time t according to a linear and a parabolic dependence. The kinetic critical size ak is determined by the intersection point between the two parts of a2(t) curves. It is shown that the results from the kinetic investigations of the basal face edge are in qualitative agreement with the basic relationships characterizing the growth kinetics of crystals in a kinetic and a diffusion regime Experimental facts are presented (e.g. the parallel running a2(t) curves, etc.) which confirm the diffusion character of the observed transition of the basal edge of zinc single crystals from a kinetic regime to a diffusion growth mode.
Crystal and molecular structure of 5‐diazo‐2,2‐dimethyl‐4,6‐dioxo‐1,3‐dioxane and 5‐diazo‐1,3‐dimethylpyrimidin‐2,4,6‐trione
Authors: Ramm M. , Schulz B. , Thurner J.‐U. , Ulbricht M. 
Published: January 2007

AbstractC6N2O4H6:Mr= 170.12, orthorhombic space group Pbca,a= 6.751(2),b= 13.669(4),c= = 16.845(4) Å,V= 1555(1) Å3,Dx= 1.248 Mgm−3,Z= 8,F(000) = 704, λ(moKα) = 0.71069 Å, μ = 1.1 mm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factorR= 0.039.C6N4O3H6:Mr= 182.14, monoclinic space group C2/c,a= 17.726(8),b= 6.191(12),c= 16.062(6) Å, β = 117.59 (3)°,V= 1562 (1) Å3,Dx= 1.549 Mgm−3,Z= 8,F(000) = 752, λ(MoKα) = 0.71069 Å, μ = 1.2 mm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factorR= 0.056.
Band tail conduction in Zn‐doped GaAs
Authors: Neumann H. , Jacobs B. , Hörig W. 
Published: January 2007

AbstractThe electrical parameters of Zn‐doped GaAs liquid phase epitaxial layers are determined in the temperature range from 77 to 300 K by Hall effect and resistivity measurements. An analysis of the experimental data yields an ionization energy of 30.4 meV for the Zn acceptor in GaAs in the dilute limit of acceptor concentration. For the Mott transition a critical hole concentration of about 6 · 1017 cm−3 is estimated. It is found that the temperature dependence of the electrical parameters is essentially influenced by band tail conduction effects at doping levels above the Mott transition.
A Study of precipitation morphology in NaCl:Sr and NaCl:Ba crystals
Authors: Reddy Katta Narasimha , Reddy A. Laxma 
Published: January 2007

AbstractSingle crystals of sodium chloride grown from melt containing different concentrations of strontium and barium have been observed to contain a second phase precipitating throughout the interior in the form of thin rods and well defined polygonal platelets. Two types of rods have been observed, one type oriented along 〈100〉 and the other along 〈110〉 directions. The platelets are variously in the form of hexagons, octagons, and rhombs. The precipitates disappear on quenching the crystal and reappear on aging the crystals under suitable conditions.
Resistance and inductance studies of Bi2−xPbxCa2Sr2Cu3Oy superconducting compounds
Authors: Muralidhar M. , Rao D. Mangapathi , Somaiah T. , Babu V. Hari 
Published: January 2007

AbstractBi2−xPbxCa2Sr2Cu3Oy compounds with (x = 0, 0.1, 0.2, 0.25, 0.3 and 0.4) were prepared by solid state reaction. The resistance and inductance results showed that transition temperature increases with increase in lead concentration. The highest value of Tc(0) observed is 109 K for Bi1.70Pb0.30Ca2Sr2 · Cu3Oy. The change of inductance per unit volume at liquid nitrogen temperature as a function of composition showed maximum change in x = 0.30 Pb‐doped sample. The results showed that the inductance change is maximum in samples which also showed highest Tc.
Filled SA phases in binary systems of terminal‐nonpolar compounds (IV). Mixtures of biswallow‐tailed compounds and nematogenic twin compounds
Authors: Pelzl G. , Humke A. , Demus D. , Weissflog W. 
Published: January 2007

AbstractThe phase diagrams of three binary systems of liquid crystals are presented whereby one component is a biswallow‐tailed compound and the second component is a member of homologous twin compounds. The most important feature of the diagrams is the occurrence of induced SA phases and reentrant nematic phases. The existence of the induced SA phase can be interpreted by the special molecular structure of the mixing components.
On chemical kinetics of silicon deposition from silane (II). Comparing 1st‐ and 0.5th‐reaction order
Authors: Kühne H. 
Published: January 2007

AbstractTheoretical expressions for silicon layer deposition from silane pyrolysis within an open isothermal reactor tube has been derived for 0.5th order of chemical reaction with restricting the discussion to homogeneous gas reaction, and compared to the analogous expressions of chemical reaction characterized by 1st order relationship. Both kinds of theoretical equations give results free from contradictions when applied to experimentally based data of silane consumption on the one hand and silicon deposition distribution on the other, at least, with respect to those data published by Puga. First order reaction is characterized by an activation energy of ΔEaSi = 34 – 39 kcal/mole, and 0.5th order reaction by ΔEaSi = 23 – 26 kcal/mole. Chemical reaction of 0.5th order is to be preferred rather than 1st order.
Effect of the relative content of Y, Ba, and Cu on the superconducting transition characteristics of the YBaCuO System
Authors: Shpeizman V. V. , Orlova T. S. , Smirnov B. I. , Markov L. K. , Engert J. , Kaufmann H.‐J. , Rudolph K. , Matz W. 
Published: January 2007

AbstractBy varying the content ratio of the initial products, nine compounds of the YBaCuO system have been produced. These were studied to find their Tc values, critical currents jc at 77 K and effects of compression stress on the U(j)‐curves. Mechanical loading has been found to result in a shift of the U(j)‐curve towards a larger current. A correlation between the critical current value, the slope of the U(j)‐curve, and the stress induced shift is shown to exist. Samples with equal absolute deviations from the stoichiometric composition reveal close properties, the better the smaller is the deviation.
The coprecipitation of zinc aluminium hydroxides (refractory‐, absorbent‐, and catalyst precursors) from aqueous solution with ammonium hydroxide: Precipitate compositions and coprecipitation mechanisms
Authors: Doherty W. O. S. , Onuchejo E. M. T. , Packter A. 
Published: January 2007

AbstractZinc aluminium hydroxide hydrates were coprecipitated from different mixed cation solutions at Zn/Al2 ratios from 1/2 to 4/1. The coprecipitations were monitored by potentiometric titrations and the final coprecipitate compositions were examined by chemical analysis and atomic absorption spectrophotometry, X‐ray diffraction and preliminary thermal analysis. The product from Zn/Al2 = 1/2 solution was amorphous: at Zn/Al2 = 1/1.5, the main phase (after drying at 95 °C) was a zinc hydroxoaluminate Zn[Al(OH)4]2 together with some gibbsite: at Zn/Al2 = 1, the main phase was probably a solid solution (of Zn[Al(OH)4]2 with Zn2[Al2(OH)10]) together with Zn2[Al2(OH)10]: at Zn/Al2 = 2, the main phase was a mixture of Zn2[Al2(OH)10] with (ZnOH)4 [Al2(OH)10] and some gibbsite: at Zn/Al2 = 4, the main phase was (ZnOH)4 [Al2(OH)10] with some zinc hydroxide.
Studies on the lattice match and strain in the epitaxial growth of III – V alloys on inas and GaSb substrates
Authors: Gnanasundaram D. , Mani V. N. , Dhanasekaran R. , Ramasamy P. 
Published: January 2007

AbstractThe compositional conditions to deposit the epitaxial films of III – V materials lattice matched to InAs and GaSb substrates have been investigated and the results are presented in the form of charts. The validity of our theoretical predictions has been tested by comparing with the available experimental results. Strain in the GaxIn1 − xAsySb1 − y quaternary alloy has been visualised as three‐dimensional perspective plots.
2‐phenyl thiazolidine — its growth and characterisation
Authors: Umarani R. , Eswaramoorthy S. , Raju K. S. 
Published: January 2007

AbstractThe importance of 2‐phenyl thiazolidine lies in its being a model for penicillin, as the five‐membered thiazolidine ring happens to be the moiety of penicillin. This material is synthesised and crystallised (Tsukerman). The crystals are white in colour, transparent, needle‐shaped and of dimensions (0.2 × 0.3 × 0.4 mm3). Employing X‐ray diffraction studies, it is found that the crystal belongs to the orthorhombic system with the unit cell parameters a = 8.388(1), b = 18.114(2) and c = 5.625(1) Å. The space group is P 212121 and Z = 4. The absorption peaks pertaining to NH, NCS, methylene CH2 and aromatic C6H4 have been identified from the infrared absorption spectrum of the sample. The Proton Magnetic Resonance (PMR) spectrum fully accounts for the hydrogens in the sample thereby unambigiously supporting the proposed structure.
Formation of high resolution X‐ray diffraction pictures of crystal imperfections, their distortionless detection and unique interpretation
Authors: Bezirganyan P. H. , Aboyan A. O. , Khzardzhyan A. A. 
Published: January 2007

AbstractA method of step‐by‐step scanning, free from all the deficiencies inherent in the known methods of projection topography is proposed. The proposed method allows one to detect high resolution, distortionless X‐ray diffraction pictures.
High‐frequency dielectric constant of AIIB2IIIC4VI ordered‐vacancy compounds
Authors: Neumann H. , Kissinger W. , Lévy F. 
Published: January 2007

AbstractThe mean high‐frequency dielectric constant of ZnIn2Se4, CdIn2Se4, ZnIn2Te4 and CdIn2 Te4 was determined from unpolarized infrared reflectivity spectra measured in the wavenumber range v̄ = 600 – 4000 cm−1. A simple relation based on the quantum dielectric theory for multibond crystals is proposed to estimate the mean high‐frequency dielectric constant of the AIIB2IIIC4VI compounds from individual bond susceptibilities. The results of the calculations are compared with existing experimental data, and susceptibilities of the HgCVI bonds are estimated.
KTiOPO4(KTP) crystal growth from high‐temperature solutions containing WO3
Authors: Shumov D. P. , Nikolov V. S. , Iliev K. N. , Aleksandrovskii A. L. 
Published: January 2007

AbstractThe process of seed growth of KTiOPO4 crystals from three different high‐temperature solutions containing WO3, with definite compositions is reported. The low viscosity and relatively slight change of the solubility of the KTP with the variation of the temperature allow the growth of adequately large crystals, free from inclusions, in the case of two tested techniques – slow cooling and temperature gradient. Conditions to avoid defects in the seed region have been found. The relatively high growth rates allow the production of crystals in a 5‐day growth run, that can be cut into samples oriented along synchronism for the second harmonic generation(SHG) with dimensions 8 × 8 × 7 mm3. SHG measurements reveal that the quality of the samples considered is comparable with KTP crystals grown from high‐temperature nonstoichiometric solutions.
Crystal and molecular structure of 6,13‐Di(ethoxycarbonyl)‐7,12‐dimethyl‐dibenzo [b.i.]‐1,4,8,11‐tetraaza[14]annulenato(2‐) nitrosocobaltat [C26H26O5N5Co] and the neutral ligand [C26H28O4N4]
Authors: Görls H. , Reck G. , Jäger E.‐G. , Müller K. , Seidel D. 
Published: January 2007

AbstractBoth title compounds crystallize in the orthorhombic space group Pnma with 4 formular units in the unit cell. The lattice parameters are: [C26H26O5N5Co], a = 8.589(4), b = 19.395(3), and c = 14.850(3) Å;[C26H28O4N4], a = 8.413(7), b = 19.166(4), and c = 14.807(28) Å. The crystal structures have been determined by direct methods and refined by full‐matrix least square calculations. The ligands have a pronounced saddle‐shaped conformation in each structure because of interactions of the methyl groups with the benzene rings. The overall conformations of the neutral ligand and the cobalt complex are remarkably similar.
On crystal growth of ammonium and potassium dichromate. A study of the shubnikov effect
Authors: Breidenstein B. , Follner H. 
Published: January 2007

AbstractGrowth and equilibrium forms of ammonium (A2/a) and potassium dichromate (P 1) have been calculated by means of the Fourier transform method of crystal morphology. Twin laws of potassium dichromate and heteroepitaxial intergrowth of both substances can be explained by partitions of space. According to Shubnikov the (001) planes of potassium dichromate crystals grown in aqueous solutions are always smooth, the parallel opposite planes, however, roughened. Wagner observed that this effect only occurs at temperatures shortly above or below 25 °C. The present investigation has shown that roughening of (001) appears at 25 °C after addition of potassium chromate to the potassium dichromate solutions. This means that the one‐sided intergrowth can be explained by a stereospecific adsorption of polychromates. Solution additions like potassium permanganate and Chromotrope 2B generate roughenings on both {001} faces. X‐Ray diffraction investigations can be interpreted in such a way that the intergrown plates are mirror symmetric oriented to two planes being normal to the a‐ and b‐axes. This is in accordance with repeated formation of intergrown plates.
Thermodynamic analysis and technology of preparation of high‐Tc superconducting system YBa2Cu3O7−x
Authors: Huan Le Van , Tuong Vu Huu , Tuong Le Thi Cat 
Published: January 2007

AbstractBy modeling the equilibrium state of the phase formation reaction of High‐Tc superconducting phase 1:2:3 (YBa2Cu3O7−x) and using the results of P‐T−x correlation investigation of some authors, the variation of Gibbs free energy (ΔGm) versus temperature has been calculated. On the basis of the variation of ΔGm, the technology procedure of preparation of phase 1:2:3 with desired x has been established to meet requirement of basic investigation and application of High‐Tc superconductors YBa2Cu3O7−x.
Structural imperfections of crystals as a result of ion implantation
Authors: Aboyan A. O. , Bezirganyan P. A. , Bezirganyan S. E. , Grigoryan A. M. , Tumasyan A. S. 
Published: January 2007

AbstractThe diffraction of X‐rays has been studied in two‐crystal interferometers, the crystals of which had equal interplanar distances and between the blocks of which a non‐diffracting zone was formed as a result of ion implantation. Also the X‐ray diffraction was studied in two‐crystal interferometers, the interplanar distances of which were different and the non‐diffracting zone between the crystals had zero width. It was shown in plane wave approximation that the Moiré patterns should not be formed in case of former interferometers and necessarily arose with the latter type interferometers.
Contribution to transition layer determination for oriented eutectic growth
Authors: Wołczyński W. 
Published: January 2007

AbstractThe thermodynamic approach to isothermal interface located within a transition layer has been presented. The proposed definition of interface has been related to Hunt and Jackson's theory of completely coupled growth. Some thermodynamic definitions of layer thickness and interface surface have been derived. The fourfold point temperature has been determined basing upon the equality of chemical potential of the components in both transition layers.
Electric Characterization of Indium Sesquiselenide Single Crystals
Authors: Nagat A. T. , Nassary M. M. , Hussein S. A. 
Published: January 2007

AbstractConductivity, Hall‐effect measurements were performed on δ‐phase In2Se3 single crystals, grown by the Bridgman method over the temperature range 150–428 K, in the directions perpendicular and parallel to the c‐axis. The anisotropy of the electrical conductivity and of the Hall coefficient of n‐type In2Se3 had been investigated. The values of the Hall coefficient and electrical conductivity at room temperature spreads from an order of RH11 = 1.36 × 104 cm3/coul, σ11 = 4.138 × 10−3 Ω−1 cm−1 and RH = 66.55 × 104 cm3/coul, σ = 0.799 × 10−3 Ω−1 cm−1 for parallel and perpendicular to c‐axis, respectively. The temperature dependence of Hall mobility and carrier concentration are also studied.