bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of Mg2+‐V‐dipoles: In the thermoluminescence of LiF2:Mg single crystal
Authors: Opyrchal H. , Macalik B. , Watterich A. 
Published: January 2007

AbstractThe thermoluminescence and radiation or thermally induced changes of the concentration of magnesium dipoles have been studied in LiF:Mg2+ crystal grown in an inert atmosphere.The evolution of the TL spectrum with γ‐radiation dose shows that the glow peaks observed at the beginning of irradiation decrease at high doses whereas new peaks, positioned at higher temperatures, appeare. Moreover, it has been found that the thermally induced recovery of the dopant dipoles, destroyed during the irradiation, strongly depends on the dose applied. The recovery curves obtained for a fixed irradiation dose dose not exhibit thermal annealing steps at temperatures, at which glow peaks occur. Further, the number of the recovered magnesium dipoles is not correlated with the quantity of light emitted during heating the irradiated crystal what is expected in respect to some of the previously proposed models.On the basis of results obtained it is proposed that the decay of the magnesium dipoles is mainly due to the dopant aggregation induced by the γ‐radiation. The role of the magnesium ions in thermoluminescent processes is discussed.
METAL CVD: A thermodynamic model
Authors: Cebulla Horst , Erben Elke 
Published: January 2007

AbstractThis paper describes a thermodynamic model for the chemical vapour deposition of metal films. The values of the equilibrium mole fractions, the metal mole flux, and the deposition rate were calculated. This dependences are discussed for the normal pressure and low pressure tantalum deposition. Experimental values are reported and compared with theoretical results.
Crystal and molecular structure of (20R)‐19‐nor‐5β,14β‐pregnane‐3β,14,20‐triol 3,20‐diacetate
Authors: Pfeiffer D. , Weiland J. , Leibnitz P. 
Published: January 2007

AbstractThe title compound (20R)‐19‐nor‐5β,14β‐pregnane‐3β,14,20‐triol 3,20‐diacetate crystallizes in the monoclinic space group P21 with 4 formula units C24H38O5 in the unit cell. The lattice parameters are a = 14.324, b = 12.569, c = 12.685 Å, β = 90.21°. The crystal structure was determined by direct methods and refined by the least‐squares procedure to the discrepancy factor R = 0.042. Bond length, bond angles, ring conformations, as well as the absolute configuration at C20 were determined. In the crystal the molecules are linked to infinite chains by two hydrogen bonds.
The crystal and molecular structure of a dioxan photoadduct of 3‐dehydro‐gibberellin A1 methyl ester
Authors: Kutschabsky L. , Kretschmer R.‐G. , Adam G. , Sung T. V. 
Published: January 2007

AbstractThe three‐dimensional structure of a dioxan photoadduct of 3‐dehydro‐gibberellin A1 methyl ester has been established as (2′S)‐3‐[dioxanyl‐(2′)]‐3‐epi‐gibberellin A1 methyl ester (1) by X‐ray analysis. The compound crystallizes in the orthorhombic space group P212121 with four molecules in the unit cell of dimensions a = 9.751, b = 22.189, c = = 10.064 Å. The final R‐value is 0.103 for 1151 reflections.
Heat capacity and thermodynamic properties of LiGaO2 from 180 to 700 K
Authors: Neumann H. , Kühn G. , Neels H. , Nowak E. , Pirl E. 
Published: January 2007

AbstractThe heat capacity at constant pressure of LiGaO2 is measured in the temperature range from 180 to 700 K. An analysis of the experimental data shows that the anharmonic contribution to the heat capacity can be described by a polynomial of fourth order in the temperature. The standard enthalpies and entropies relative to 298.15 K are calculated from the measured heat capacity. Estimates of the standard enthalpy and entropy at 298.15 K are given.
X‐ray diffraction effects from 2H crystals undergoing transformation to the 4H structure by the shear mechanism
Authors: Sebastian M. T. 
Published: January 2007

AbstractThe 2H or ABAB… structure may be transformed to the 4H or ABCB… structure if deformation faults occur in a non‐random manner. The theory of X‐ray diffraction from one‐dimensionally disordered crystals undergoing the 2H → 4H structural transformation by the deformation mechanism is developed. For this it is necessary to consider that the faults are not distributed entirely at random but tend to occur in such a manner as to statistically create a 4H structure. The X‐ray diffraction effects are predicted.
Simplified treatment of transient doping behaviour in CVD (II)
Authors: Arnold H. 
Published: January 2007

AbstractUsing circuit representations, the influence of the deposition rate for semiconducting CVD layers on transient behavior of doping concentrations is rechecked for a simple decomposition reaction of the dopant species. The existence of a space‐charge region below the surface is taken into account. Simple estimations show that atomically abrupt doping transitions are to be expected, if the storage of foreign atoms in the surface is responsible for transient behaviour, and if their concentration becomes frozen in. In order to explain flatter doping profiles occurring with As and P in Si, molecular storage has to be included in the study. Only some simplified cases with one capacitance, or a sum of capacitances, in the circuit representation are being treated.
Growth and removing of tungsten whiskers under controlled conditions
Authors: Aleksandrov L. N. , Mordyuk V. S. , Tokarev A. T. , Rubtsov A. A. 
Published: January 2007

AbstractThe growth kinetic and size decreasing process of tungsten rod‐like crystals by heating in the iodine vapour are studied. Effects of tungsten filament temperature (2400 – 3500 K), iodine concentration (to 6 mg/cm3) and water contents (0.01 – 0.05 mg/cm3) are shown. Maximal growth rate of tungsten whiskers to 30 μm/min. Stopping of the growth and following removing by iodine reactions take place after heating to 3500 K.
Pyroelectric, dielectric, piezoelectric and electrooptic properties of monoclinic nitrilotriacetic acid N(CH2COOH)3 and orthorhombic X2Zr[N(CH2COO)3]2 · 2 H2O (X = K, Rb, Cs)
Authors: Richter U. , Haussühl S. 
Published: January 2007

AbstractLarge single crystals of monoclinic nitrilotriacetic acid, N(CH2COOH)3, NTA, and of orthorhombic isotypic X2Zr[N(CH2COO)3]2 · 2 H2O (X = K, Rb, Cs) have been grown from aqueous solutions. They possess optical quality and have dimensions up to 10 mm and larger. The complete dielectric, piezoelectric and electrooptic tensors have been determined. The maximum longitudinal and transversal piezoelectric effects exceed those of α‐quartz by roughly a factor 11. The pyroelectric effects in NTA and in the X2Zr‐salts (X = K, Rb, Cs) are by about a factor 3 larger than that in tourmaline, whereas the maximum electrooptic effects amount only to about half of that in KH2PO4. Qualitative measurements of the nonlinear optical properties by the aid of a SHG powder test and on single crystals revealed effects comparable with those observed in LiIO3. Phase matching is possible in these compounds. Replacing X by NH4 or Tl also acentric crystals are obtained with strong polar properties.
Phase transition of nematic to smectic C through an intermediate boundary induced smectic A structure
Authors: Simova P. , Petrov M. 
Published: January 2007

AbstractAn intermediate phase has been observed at the transition nematic to smectic C where a smectic A structure induced by the boundaries and a nematic phase exist simultaneously. The temperature interval of existence of the intermediate phase is of the order of one tenth of degree. Several conditions are necessary for its appearance: the latent heat L of the phase transition nematic‐smectic C of the liquid crystal should be sufficiently small (L < kBTc); the nematic phase should undergo a bend deformation by the boundaries (possibly a twist one as well) and the transition nematic‐smectic C should be carried out as slower as possible.
Growth of KDP single crystals by temperature reduction under diffusion transport
Authors: Santos A. , Garcia‐Ruiz J. M. 
Published: January 2007

AbstractGrowth rates of 37 μm/hour for {010} faces and 40 μm/hour for [001] directions have been found for KDP crystals growing in gelled media by temperature reduction. These values, higher than those recorded in alcohol‐diffusing techniques are in the range of more classical methods. A device for obtaining larger crystal size is also described.
On the bindings in the elements between V and Ga. 2. Phases from Co to Ga
Authors: Schubert K. 
Published: January 2007

AbstractThe analysis of bindings in the elements V to Fe (Part I) may be continued for the elements Co to Ga, so that further independent experimental data find a unified interpretation. The following explanations may be mentioned: (1) the occurrence of the Mg type at n = 9, (2) the valence electron concentration N = 0.6 at n = 8, 9, 10, (3) the tetragonal structures at n = 11, (4) the anomalous dependence of the structural axial ratio on n near n = 11, (5) the anomalous crystal axial ratio at n = 12, etc. A useful analysis parameter is the site number ratio N going through a maximum at n = 8, 9, 10 and causing thus the close chemical relationship of Fe, Co, Ni. One of the physical conditions for the phenomena is the high compliance of the correlation in the d‐band (e correlation) permitting predominantly a full occupation ceasing only at n = 13. The diversity of interpreted phenomena not understood earlier provides a corroborating support to the hypotheses of the plural correlations model.
The current understanding of epitaxial CVD silicon doping in the light of modelling and theory development (II). Theoretical foundations and incorporation equations
Authors: Kühne H. 
Published: January 2007

AbstractTheoretical foundations selected from related fields of science (thermodynamic and chemical equilibria, kinetics of surface‐catalized reactions, open systems and steady‐state equilibria, solid‐state physics of semiconductors) are applied to epitaxial silicon layer doping to reveal the doping process mechanism. In this way it is shown how the empirically based relationships between the controlling parameters of the process and the doping effect (c.f. part I) can be explained by theory. In the course followed, the historical evolution is neglected in favour of the logical interconnection between the empirical and theoretical foundations.
Crystal growth and domain structure of triglycine sulphate doped with Pt(II)
Authors: Březina B. , Havránková M. 
Published: January 2007

AbstractThe single crystals of triglycine sulphate doped with bivalent Pt‐ions (TGS‐Pt) were grown in full‐shaped form, i.e. with many growth sectors. The domain structure of individual growth sectors was studied by the liquid crystal method. The growth sectors are mostly in a single domain state but spontaneous polarization is reversed in growth sector boundaries, which coincide with charged domain walls. Only the growth sector 001 reveals a blockshaped domain structure, however it differs from usual lenticular domains of the undoped TGS. The concentration of Pt in various growth sectors is different. The growth sectors with the higher concentration of Pt than 3 × 10−2% exhibit the unipolarity stable against thermal schocks.
Microstructures of gel‐grown ammonium hydrogen tartrate single crystals
Authors: Desai C. C. , Hanchinal A. N. 
Published: January 2007

AbstractSingle crystals of ammonium hydrogen tartrate (AHT) have been grown in silica gels by employing the controlled reaction between ammonium chloride and tartaric acid. Transparent AHT crystals upto 24 × 4 × 3 mm3 in size have been grown at room temperature. Optical and electron‐optical studies have been made on the various surface structures of {010} faces of the grown crystals. A variety of growth striations and growth hillocks have been observed. Growth layers modified by the presence of misaligned microcrystals have been illustrated. It has been suggested that two‐dimensional nucleation, spreading and pilling up of growth layers is mainly responsible for the growth of these crystals and the implications are discussed.
Electrical conduction in ferroelectric lead hydrogen phosphate single crystals
Authors: Desai C. C. , Ramana M. S. V. 
Published: January 2007

AbstractSingle crystals of LHP (Lead Hydrogen Phosphate) have been grown using the controlled reaction between lead nitrate and orthophosphoric acid solution by diffusion process in silica gel medium. Transparent crystals upto 6 × 4 × 3 mm3 in size have been grown at room temperature. The d.c. electrical conductivity of both single crystals and pelletized samples of LHP have been studied in the temperature range from 313 to 968 K. It has been observed that: (i) the d.c. conductivity of the crystalline sample is greater than that of thepellet sample, (ii) three distinct electrical conductivity processes have been observed and are interpreted as extrinsic, intrinsic, phase changes, and (iii) the activation energy for the conduction in the crystalline sample is greater than that of the pellet sample. The magnetic susceptibility measurements reveal that the paramagnetic characteristic of these materials and the implications are discussed.
Dielectric studies on binary mixtures containing 4‐trans‐4′ ‐n‐hexyl‐cyclohexyl‐isothiocyanato‐benzene
Authors: Raszewski Z. , Dąbrowski R. , Stolarzowa Z. , Zmija J. 
Published: January 2007

AbstractWe have studied binary mixtures with an induced smectic phase of 4‐trans‐4′ ‐n‐hexylcycohexyl isothiocyanatobenzene (6CHBT) with 4‐n‐ethyl‐4′‐pentylazoxybenzene (EPAB) by means of dielectric, microscopic and refractometric measurements. The effective values of components p ⟂ and p∥ of the dipole moment per one molecule of the mixture have been calculated from values of ϵ ⟂ and ϵ ∥. As a result of our studies, we have established that the heterocomplexes formed in the mixture are so weak that they do not cause any essential changes in the distribution of molecule charges. The observed deviations from additivity of the dielectric constant of the mixture are caused solely by a non‐additive behavior of the mixture density.
X‐ray quantitative determination of the phases in a batch for the synthesis of poly‐ and monocrystal yttriumaluminium garnet
Authors: Petrov Sr. , Chomakov Iv. , Bogdanov B. I. 
Published: January 2007

AbstractFor the synthesis of ceramics and single crystals of yttriumaluminium garnet, a batch consisting of Y2O3 and Al2O3 is first treated thermally in order to obtain the garnet phase Y3Al5O12. It is possible to make a choice of the optimum technological parameters of the batch if the amounts of all oxide phases, present during the synthesis, are well known.A combined X‐ray quantitative method is suggested for this purpose. The initial oxides and a garnet phase are determined by the method with external standard. The rest two impurity oxide phases are determined as binary system. The specific diffraction characteristics of the present compounds were taken into account. The amounts of all phases in the batch, treated thermally from 1373 to 2075 K at every 100 K are shown.
Optical, X‐ray, and calorimetric studies of phase transitions in ND4BeF3
Authors: Waśkowska A. , Pietraszko A. , Czapla Z. 
Published: January 2007

AbstractPhase transitions in ND4BeF3 crystals at T1 = 330 and T2 = 245 K were studied by specific heat (DSC) and X‐ray lattice parameters measurements in function of temperature. These ferroelastic transitions are accompanied by anomalous heat absorption, sudden changes in the unit cell parameters and crystal symmetry. Formation of domain structure in particular phases examined under a polarizing microscope is also described. Domain walls of the type (100), (010), and (001) observable at room temperature indicate on the triclinic symmetry of the Phase II. Above T1 the crystal becomes orthorhombic. First‐order phase transition at T2 causes the symmetry of the crystal in the Phase III to be monoclinic with the c‐axis unique. The phase transition diagram is proposed and compared with the phase situation in nondeuterated NH4BeF3 crystals.
Electrical conductivity of some mixed ferrites at Curie Point
Authors: Reddy P. Venugopal , Pratap K. J. , Rao T. Seshagiri 
Published: January 2007

AbstractThe behaviour of electrical conductivity of four ferrite semiconductor systems viz., Li‐Ni, Mn‐Mg, Co‐Zn and Ni‐Zn having different compositions has been studied in the vicinity of magnetic transformation temperature. Contrary to the predictions of an empirical formula (PARKER's) all the ferrites under investigation have exhibited marked and clear transitions at the Curie Point.
The precipitation of aluminium hydroxocarbonates powders from aqueous solution: Precipitate compositions and precipitation mechanisms
Authors: Packter A. , Panesar K. S. 
Published: January 2007

AbstractA series of aluminium hydroxocarbonate hydrates were prepared by precipitation from aluminium nitrate solution, with five sodium hydrogen carbonate‐sodium carbonate solutions of different pH, at ambient temperature. The course of precipitation was monitored by pH measurement and the final precipitate compositions were determined by chemical analysis, infra‐red spectrophotometry, X‐ray diffraction and thermal analysis.Precipitation generally occurred through three stages, primary precipitation of materials with low carbonate content at low pH with evolution of carbon dioxide, their dissolution to form hydroxcarbonato anions and then secondary reprecipitation of the final products at higher pH. These materials were mixtures of polyhydroxoaluminium carbonate hydrates of general composition Aln(OH)3n‐2CO3 · hH2O (where n = 2, 4, 6 and h = 6–8); their CO3 content increased with increasing pH and carbonate anion content of the precipitant solution.
The effect of manganese additions on the structure changes proceeding in rapidly solidified Al‐Cu alloys
Authors: Dzuong Lecong , Löffler H. , Thang Nguyen Quyet , Tri Hoang Minh 
Published: January 2007

AbstractThe effect of Mn additions (0… 2 wt%) on the decomposition of rapidly solidified Al‐4.0 wt% Cu alloys (cooling rate 103 to 104 K/s; LQ treatment) were studied during ageing between RT and 450 °C by hardness, X‐ray methods and electron microscopy. The results were compared with alloys homogenized in the region of the solid solution (SQ treatment).(i) The LQ treatment results in a quite better homogeneous distribution of the alloyed elements than the SQ one, that is less particles of intermetallic phases are present in the ascast state. (ii) At T < 250 °C Mn additions affect the decomposition kinetics by trapping of vacancies (retardation) and the diminution of the solubility of Cu atoms (acceleration). The first effect dominates in the stage of G.P. zone formation, the second one during precipitation of intermediate phases. (iii) At T ≧ 300 °C the intermetallic compound Cu2Mn3Al20 forms associated with a significant increase of the hardness.
An X‐ray diffraction refinement of the crystal structure of natural apophyllite
Authors: Pechar F. 
Published: January 2007

AbstractThe crystal structure of apophyllite (Andersberg — GDR), with a = 8.966(2), c = = 15.767(1) Å, P4/mnc, z = 2, Q = 2.35 gm · cm−3, has been refined (R = 0.035) by least squares with 976 reflections collected with a diffractometer. Apophyllite is a sheet structure with the bringing SiO bond lengths 1.6236 Å, while the non‐bridging bond length SiO(3) is 1.5843 Å. The two independent SiOSi angles are 140.09, 140.76 degrees. The mean SiO bond length is 1.6138 Å.As it was not possible to locate unequivocally the H‐atoms with the X‐ray data, the interpretation of the of water in the structure was based on the charge balance approach of DONNAY and ALLMAN. Assuming that the fluorine ion is bonded to calcium ion (Ca‐F = = 2.416 Å) and to H3 atom (F‐H3 = 0.9145(1) Å) and water molecule hydrogen bonded to silicate framework. The average bond distances O‐H are 0.962(2) Å and angle 105.24(1)°.
X‐ray investigation of the mechanisms of phase transformations in single crystals of ZnS, ZnxCd1−xS, and ZnxMn1−xS (II). Comparison of observed and calculated diffraction effects
Authors: Sebastian M. T. , Krishna P. 
Published: January 2007

AbstractThe experimentally observed intensity profiles recorded from ZnS, ZnxCd1−xS and ZnxMn1−xS crystals at different stages of the 2H‐3C and 2H‐6H transformations are compared with those computed theoretically from the three parameter model in the previous paper. It is found that the 2H‐3C and 2H‐6H transformations occur by the nonrandom nucleation of deformation faults. The probability of the growth of a nucleus is much greater than that of the creation of a fresh nucleus. At least two different fault probabilities have therefore to be employed in computing the diffraction effects in each case. The transformation behaviour of ZnxCd1−xS and ZnxMn1−xS crystals is strongly influenced by variations in stoichiometry (x). Large values of x (x > 0.95) favour the 2H‐3C transformation, whereas smaller values (x ≦ 0.94) favour the formation of the 6H phase. A comparison of the calculated and observed intensity distributions indicates that in some crystals the 2H‐3C and 2H‐6H transformations occur simultaneously in different regions of the same single crystal.
Crystal and molecular structure of Bis(glyoxal‐bis‐tert.butylimine)nickel(0)
Authors: Görls H. , Walther D. , Sieler J. 
Published: January 2007

AbstractThe crystal structure determination of the title compound was undertaken to determine the coordination geometry of nickel atom. Bis(glyoxal‐bis‐tert.butylimine)nickel(0) (C20H40NiN4) crystallizes in the space group Pna21 with Z = 4, a = 18.546(6), b = 9.331(8), and c = 13.505(8) Å. The structure was solved by the heavy atom method and refined to R = 0.065. The molecule has four‐coordinate nickel atom. The coordination geometry about the nickel atom is tetragonal.
X‐ray determination of thermal expansion of Na(ClO3)x(BrO3)1−x mixed crystals
Authors: Subhadra K. G. , Hussain K. A. 
Published: January 2007

AbstractLattice constants of sodium chlorate and sodium bromate and their mixed crystals were determined over the temperature range from room temperature to 320 °C. The observed lattice constants for the various compositions show strong deviations from those expected from Vegard's rule. The lattice constants at various temperatures were fitted to polynomials of type a = a0 + a1t + a2t2. The linear coefficients of expansion for the Na(ClO3)x · (BrO3)1−x series varies non‐linearly with composition showing negative deviations from linearity.
Infrared optical properties of Cu1−xLixSe2 thin films
Authors: Sobotta H. , Neumann H. , Mitaray S. , Riede V. , Kühn G. 
Published: January 2007

AbstractInfrared absorption spectra of Cu1−xLixInSe2 thin films are measured at room temperature in the wavenumber range from 100 to 600 cm−1. The spectra exhibit two absorption bands in the wavenumber ranges 200–210 cm−1 and 330–355 cm−1 which are ascribed to vibrational modes due to InSe and LiSe vibrations, respectively. The influence of the phase transition from the chalcopyrite structure to the β‐NaFeO2 structure in the composition range x = 0.5–0.6 on the vibrational characteristics is established and discussed.
Hyperfine structure of Cr5+ EPR spectra in X‐irradiated potassium halide crystals doped with CrO and Ca2+
Authors: Akchalov Sh. , Alybakov A. , Zhanibekov M. , Karashev T. K. , Tojchiev N. 
Published: January 2007

AbstractThe hyperfine structure has been investigated in the EPR spectra of X‐irradiated KCl: CrO, Ca2+ and KBr: CrO, Ca2+ crystals. Preliminarily spectra were simplified by means of heating the crystals up to 400 K for KCl and 440 K for KBr, that destroys the less stable CrO · V centers. It is ascertained, that principal directions of g‐ and A‐tensors do not coincide, and principal A‐values are determined. Calculations, making use of the experimental meanings of g‐ and A‐tensor components, showed, that the degree of distortion of oxygen tetrahedra in CrO · Ca2+ · V centers is almost the same in both KCl and KBr crystals; besides, these calculations suggest the existence of a strong covalent bonding between the central Cr5+ ion and four oxygen ligands in CrO ions.