bluuebunny/crossref_metadata_2025_split huggingface dataset:
Satatistical Model of Mechanoluminescence in Crtstals
Authors: Chandra B. P. , Rahangdale Yuvaraj , Ramrakhiani Meera , Aansari M. H. , Sharma Y. K. 
Published: January 2007

AbstractThe present paper reports on a statistical model of the mechanoluminescence (ML) excitation in crystals where attempts have been made to explain stress, temperature‐, strain rate‐, activator concentration dependence and several other aspects of ML. It is found that ML emission should take place only during the period at which stress will change with time. The total ML intensity should be directly proportional to the square of the stress and there should be phase difference between the ML pulse and the applied stress pulse. It is found that the ML intensity should decrease faster with temperature as compared to the corresponding photoluminescence intensity. within the limit of concentration quenching the ML intensity should increase directly with the defect centre concentration. The ML intensity should increase with the stress rate or strain rate of the solids. Furthermore, the concept of mechanoluminescent and non‐mechanoluminescent materials is explored.
Single Crystal Growth and Electrical Properties of Gallium Monotelluride
Authors: Gamal G. A. , Nassary M. M. , Hussein S. A. , Nagat A. T. 
Published: January 2007

AbstractSingle crystals of GaTe were prepared in our laboratory by a special modified Bridgman technique method. Measurements of the electrical conductivity and Hall effect between 210 and 450 K were carried out on GaTe samples in two crystallographic directions. The Hall coefficient is positive and varies with the crystallographic direction. A unique mobility behaviour and strong anistropy in the carrier mobility were observed. The Hall mobilities parallel and perpendicular to the C‐axis, at room temperature, were 12 cm/V · s and 25.12 cm2/V ·s, respectively. The free carrier concentration lies between 1013 − 1014 cm−3 at room temperature.
Formation Volume of Vacancies in Elements and the Defect Formation Mechanism of Melting
Authors: Bollmann W. 
Published: January 2007

AbstractThe formation volumeVvof vacancies is given byVv= (hv/L) ΔVfwithhv= 8L(formation enthalpyhvof vacancies and heatLof fusion given in same units; ΔVf= change of volume due to melting). If there are phase transitions within the solid,Land ΔVfmust be replaced by (L+ ΔHt) and by (ΔVf+ ΔVt), respectively (ΔHtand ΔVtrefer to the heat (s) of transition (s) and to the volume change(s) due to transition(s), resp.). The pressure dependence of the melting point is dTm/dp= (TmVv)/hv. Independent of the sign ofVvany increase of the vacancy concentration above the maximum concentration possible within the solid decreases the melting point thus resulting in the observed surface melting. The melting point is fixed by the characteristics of vacancy formation (hv,Sv,Vv) and by the bulk modulus of the solid (Sv= formation entropy of vacancies).
Investigations on the Quasi‐binary System V2O5Ta2O5
Authors: Schadow H. , Oppermann H. , Wehner B. 
Published: January 2007

AbstractBy chemical transport reactions, in the system V2O5Ta2O5 another two compounds already described in literature were successfully isolated besides the two boundary phases. These are VTa9O25 and the compound VTaO5 occurring in two modifications. The transition point of the irreversible change of modification α‐VTaO5 → β‐VTaO5 was determined as 1153 ± 5 K in a quite good agreement with values cited in the literature.
Debye‐Waller Factors and Elastic Constants for Beryllium Oxide at Temperatures between 10 and 720 K (II). Elastic Constants from X‐ray Diffraction Data
Authors: Sirota N. N. , Kuzmina A. M. , Orlova N. S. 
Published: January 2007

AbstractThe method for determining the full elastic constants tensor for hexagonal crystals from the characteristic Debye temperatures obtained by X‐ray diffraction technique in different crystallorgraphic directions is given. All five elastic constants at different temperatures between 10 and 720 K for beryllium oxide with wurtzite structure are calculated using this method.
The Microhardness and the Toughness Anisotropy of Paratellurite Single Crystals in the Tr — 650 °C Temperature Range
Authors: Lomonov V. A. , Pisarevski Yu. V. , Sizova N. L. , Silvestrova I. M. , Dohnovskaya S. I. , Cholokov M. N. 
Published: January 2007

AbstractThe temperature hardness (Hv) and toughness (K1C) dependence of paratellurite (100), (010), (001) planes is investigated in the Tr −650 °C range. The correlation between the anisotropy degree of Young modulus and Hv is not found. The presence of 11 kind Hv and K1C anisotropy is shown.
Tribochemical Synthesis of Magnesium Zirconate for Some Specific Purposes
Authors: Gospodinov G. G. , Marchev V. M. 
Published: January 2007

AbstractMgZrO3 was synthesized by tribochemical and thermal treating of a mixture of MgO and ZrO2 corresponding to its stoichiometry. The gained compound is identified by chemical and X‐ray analysis.
Rietveld Analysis of Mechanically Activated Powdered Zinc Ferrite
Authors: Šepelák V. , Tkáčová K. , Rykov A. I. 
Published: January 2007

AbstractThe mechanically induced changes in structure and magnetic properties of zinc ferrite were investigated by using the Rietveld analysis and Mössbauer spectroscopy. The formation of the spin arrangement in mechanically activated zinc ferrite is connected with a redistribution of the cations in the close‐packed anionic sublattice. On the basis of the Rietveld analysis the degree of mechanically induced inversion as well as the exact coordinates of atoms and lattice parameters in non‐activated and mechanically activated ZnFe2O4 was determined.
The Relation between Structure and Morphology of Magnetoplumbite‐type Crystal LaMgAl11O19
Authors: Jun Xu , Xiaoshan Ma , Xinmin Zhang , Yafang Shen , Guangzhao Wu 
Published: January 2007

AbstractThe magnetoplumbite crystal LMA is grown by the CZ technique. The orientations of all developing facets on the crystals are determined by means of X‐ray and optical methods, and Miller indices are calculated. According to the PBC theory, the relations between the morphology of LMA crystal and its structure are explained.
Phase Transition of Magnesium Sulphite Hydrates in Aqueous Suspension
Authors: Söhnel O. , Rieger A. 
Published: January 2007

AbstractSolution mediated phase transitions in aqueous suspension (pH 9.5) of MgSO3 hydrates were studied at 50, 60, 65, and 70 °C for hexa‐ to trihydrate and 25, 30, and 35 °C for tri‐ to hexahydrate conversion. The former conversion is controlled by the diffusion growth of the new phase crystals whereas the latter process is controlled by both the initial phase dissolution and the new phase growth.
On the Formation of Thick Sector Boundaries by Appearance and Disappearance of Faces of Crystals
Authors: Szurgot Marian 
Published: January 2007

AbstractWide sector boundaries revealed in KBC crystals by chemical etching have been observed and analysed. It was established that the boundaries represent sectors of small faces appearing and vanishing in the habit during crystal growth. This nature of thick boundaries has been confirmed by the analysis of values of relative growth velocities of faces with respect to the critical velocities governing the presence of faces on growing crystals.
The Influence of Interstitials and Growth Conditions on the X‐Ray Colorability of Synthetic Quartz Crystals
Authors: Bernhardt Hj. 
Published: January 2007

AbstractThe saturation colorability of quartz crystals depends not only on the contamination of the material but also on the regarded growth sector. But even in the same sector the colorability varies locally. Investigations of crystals with induced growth striations and defined local growth rate showed that the dependence of the colorability on the growth conditions is very complex. The growth rate to colorability characteristics may have positive or negative slopes regarding e.g. —x‐or z‐sections. Optical investigations of —x‐sections prove that under certain circumstances light and/or dark striations may occur or even uncolorable regions may be observed, althought the contamination is sure. We explain this by the interaction of the coloration centres with interstitials. That effect might be of importance for the evaluation of the impurity by means of the coloration of natural or synthetic quartz crystals.
Dielectric Properties of Beta Barium Borate and Potassium Pentaborate Single Crystals
Authors: Raja C. Ramachandra , Gobinathan R. , Gnanam F. D. 
Published: January 2007

AbstractSingle crystals of beta barium borate and potassium pentaborate (commonly known as β‐BaB2O4 or BBO and KB5O8. 4 H2O or KB5) were grown by high and low temperature solution growth methods, respectively. The dielectric constant and loss tangent were determined as a function of temperature. Frequency response of the dielectric constant and tan δ have been studied over a frequency range of 0.1 −100 kHz; it is found that both the dielectric constant and tan δ decrease with increase in frequency for both crystals. The dielectric constant and tan δ are found to increase with increase in temperature for both the crystals. Further, the dielectric constant and tan δ measured on different orientations of the grown crystals reveal the anisotropic nature of the crystals.
The Discovery of the Diffraction of X‐rays in Crystals — A Historical Review
Authors: Hildebrandt G. 
Published: January 2007

AbstractThe history of the discovery of X‐ray diffraction in crystals and its first sequels are reported; the life of M. v. Laue, the discoverer and founder of a first basic theory, and of P. P. Ewald, who contributed to the discovery and to later developments of the theory, are shortly described.
A Statistical Thermodynamics and Growth Restrictions (STGR) Model of Polytypism with Special Reference to Zinc Sulfide
Authors: Ahmad Shandar , Wahab M. A. 
Published: January 2007

AbstractA model to explain polytypism based upon classical statistics and the idea of minimum sandwiches of basic phases has been developed. Presence of two or more phases under suitable thermodynamic conditions and restrictions imposed by statistical, structural, and growth factors have been elaborated. A new statistical approach is used and a criterion to find most probable polytypes of a compound has been evolved. Logical implications of the model are found in good agreement with the experimental data.
The Hydrothermal Effect on Crystal Development and Electrical Conductivity of Li2CO3
Authors: Ghobarkar Habib , Schäf Oliver 
Published: January 2007

AbstractLithiumcarbonat was treated hydrothermally in the range of temperature from 80 °C to 600 °C. The Li2CO3‐crystals of the starting material were monoclinic with the unit cell a = 8.39 Å, b = 5.00 Å, c = 6.21 Å, β = 114.5° and the space group C2/c (Zemann). During the increase of temperature the habit of the Li2CO3‐crystals changed in the ranges of higher temperatures that they could be described as pseudocubic. In parallel with this development the electrical conductivity of the crystals also changed.
Growth and Characterisation of Pure and Nickel‐doped Strontium Tartrate Tetrahydrate Single Crystals
Authors: Rethinam F. Jesu , Oli D. Arivu , Ramasamy S. , Ramasamy P. 
Published: January 2007

AbstractStrontium tartrate tetrahydrate single crystals doped with nickel have been grown in silica gel. The grown crystals have been characterized by X‐ray, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and etching technique.
Growth Morphology and Structure Peculiarities of Superthin Titanium Films
Authors: Mikhailov I. F. , Borisova S. S. , Fomina L. P. , Babenko I. N. , Melnik N. N. , Pudonin F. A. 
Published: January 2007

AbstractSuperthin titanium films of 0.3 to 2 nm thickness, prepared by radio‐frequency sputtering, have been studied by modern X‐ray methods, such as reflectometry, fluorescent analysis and grasing‐beam structural analysis. Two simple models were used to describe early stages of film growth. It has been shown that the thinnest titanium films were the TiO2 islands with an equal height. Thicker films could be described as bilayers Ti/TiO2. The films became continuous already near 1.5 nm effective thickness.
High‐temperature Raman Investigations of Arsenic Vapour
Authors: Herms M. , Wunderwald U. , Irmer G. 
Published: January 2007

AbstractRaman spectra of arsenic vapour were measured at temperatures up to 1210 K. The intensity ratio of the vibrational modes was used to determine the partial pressure ratio of As2 and As4.The data obtained exhibit discrepancies to existing theoretically predicted values. The reason for these differences is yet unclear.
Magnesium Sulphite Hexahydrate Supersaturated Solutions Stability
Authors: Söhnel O. , Rieger A. 
Published: January 2007

AbstractWet purification of crude MgSO3 · 6 H2O obtained at flue gases desulphurization is based on its dissolution, separation of solid ash followed by crystallization of a clear supersaturated solution. The stability of supersaturated solutions during ash separation represents a requisite condition for realization of this process. The stability of agitated supersaturated solutions containing from 5 to 8 wt% of MgSO3 is assessed in the temperature range from 80° to 95 °C based on experimentally determined induction period of crystallization, tind, and desupersaturation curves. Time necessary for complete dissolution of MgSO3 · 6 H2O at the studied conditions, tD, is also determined. A plot of (tind – tD) versus solution initial supersaturation facilitates selection of suitable processing conditions for the wet purification.
Electron Microscopy and X‐ray Study of the Growth of FeCr2S4 Spinel Single Crystals by Chemical Vapour Transport
Authors: Volkov V. V. , Van Heurck C. , Van Landuyt J. , Amelinckx S. , Zhukov E. G. , Polulyak E. S. , Novotortsev V. M. 
Published: January 2007

AbstractThe growth features of FeCr2S4 spinel single crystals prepared by chemical vapour transport were studied by means of scanning electron microscopy, transmission electron microscopy, high resolution electron microscopy, electron diffraction and X‐ray analysis. Our results indicate that the epitaxial growth of the new phases FeCr7S12 and FeCr8S12, both based on the NiAs structure, can essentially inhibit the growth of large FeCr2S4 spinel single crystals in the octahedral habit. The new phases are fully characterised and the effects of defect ordering in these new phases are also reported.
Formation of Hydrogen‐Bonding Adduct between 1‐Phyenyl‐2‐Amino Pyrimidine and Vaniline, C17H13N3O2
Authors: Farag I. S. Ahmed , Gad A. M. , El‐Shabiny A. M. , Rybakov V. B. 
Published: January 2007

AbstractThe adduct compound was prepared by condensation of equimolar quantities of analar vaniline and 1‐phenyl‐2‐amino pyrimidine in absolute ethyl alcohol. Prismatic crystals were obtained with the crystallographic data: a = 12.901 (6), b = 19.297 (9), c = 6.828 (3) Å, γ = 102.67 (2)°, V = 1657.9 Å3, Z = 4, F.W. = 291.31, Dx = 1.17 g/cm3, space group P2/n, R = 0.038 and Rw = 0.036.The intensity data were collected on an Enraf Nonius CAD‐4 computer controlled diffractometer using MoKα radiation. The structure was solved by direct method and refined by full matrix least‐squares using anisotropic temperature factor of all atoms, except for hydrogen ones, which were treated isotropically. A full discussion was given to explain: a) the occurrence of the condensation process between the OH‐group of vaniline and the heterocyclic N‐atom in position 5 of the pyrimidine cycle and b) why this condensation does not take place between the amino‐group of the pyrimidine compound and the aldehydic group of vaniline to give a Schiff base.
Vibrational Studies of Magnesium Hydrogen Phosphate‐ and Barium Hydrogen Phosphate Crystals
Authors: Kolandaivel P. , Parthipan R. , Selvasekarapandian S. 
Published: January 2007

AbstractMagnesium hydrogen phosphate and Barium hydrogen phosphate crystals were grown in the presence of sodium meta silicate (sol‐gel method). Raman and IR spectra were measured for the above crystals. Vibrational assignments were made for both the crystals. The large shift of the stretching and bending modes of water from the free state values indicates the different hydrogen bonds strenghts present in the magnesium hydrogen phosphate crystals.
Structural Aspects of Dehydration Processes in Rubidium‐, Potassium‐ and Sodium p‐Nitrosophenolates
Authors: Milart P. , Kapturkiewicz‐Kowal E. , Borzecka‐Prokop B. 
Published: January 2007

AbstractRubidium p‐nitrosophenolate has been prepared and characterized by means of IR spectroscopy and XPD methods. Differences of dehydration processes of the rubidium salt and relative potassium‐ and sodium p‐nitrosophenolates have been detected by DTA/TG studies and discussed in terms of crystallochemically inequivalent types of water molecules in these salts.
The influence of HF on the incorporation of silicon into the erionite‐like AlPO4‐17 molecular sieve
Authors: Lohse U. , Jancke K. , Löffler E. , Schaller T. 
Published: January 2007

AbstractThe synthesis of SAPO‐17 with high silicon content (up to 18 weight‐%) succeeded with the addition of HF to the reaction mixtures. The characterization of the samples with chemical analysis, XRD, and adsorption measurements show the incorporation of silicon into tetrahedrally coordinated framework positions. Spectroscopic methods (IR, 19F MAS NMR) demonstrate the presence of fluorine in the as‐synthesized samples. The effect of the fluorine consists in (i) the improvement of the silicon incorporation into framwork positions, (ii) the stabilization of the as‐synthesized samples and (iii) the charge compensation of the template ion by F−.
Stoichiometric defects and volume diffusion in epitaxial PbTe‐SnTe multilayers
Authors: Fedorov A. G. , Galkina E. V. , Mikhailov I. F. , Shpakovskaya L. P. 
Published: January 2007

AbstractThe effect of annealing on multilayer structures based on epitaxial layers of PbTe‐SnTe was investigated by X‐ray diffraction profile changes. Decrease of satellite reflections intensity and conversion of pattern asymmetry were found. Profiles of interplanar distance and electron density deviations were determined by solving both the direct problem (numerical computation of Takagi‐Taupin equations) and the inverse problem (optimisation task) according to the average lattise model. Computation showed the presence of interlayer area of PbSnTe composition containing up to 8% of stoichiometric vacancy type defects between PbTe and SnTe layers. Two diffusion mechanisms are proposed: “fast” diffusion connected with occupation of stoichiometry defects and “slow” substitutional diffusion.
X‐ray determination of thermal lattice expansion of CuSi2 + xP3 (x = 1, 2) at elevated temperatures
Authors: Bhikshamaiah G. , Omar M. S. , Suryanarayana S. V. 
Published: January 2007

AbstractCuSi2P3 is a semiconductor having sphalerite structure with the space group F33m with random distribution of the copper and silicon atoms on the cation sites. Silicon is soluble in CuSi2P3 upto 3 moles to form CuSi2 + xP3 (x = 1, 2, 3) compounds in single phase. In continuation of our work on thermal expansion of ternary semiconductors, CuSi3P3 crystals have been grown by a modified Bridgman method. Using a Unicam high temperature camera, the precision lattice parameter and the coefficient of thermal expansion (CTE) of CuSi3P3 at various high temperatures have been evaluated from X‐ray diffraction data. It has been found that the lattice parameter increases non‐linearly while the coefficient of thermal expansion increases linearly with temperature. The results on thermal expansion of various semiconductors have been discussed in terms of their ionicities.
A rietveld study of the cation substitution between uvarovite and yttrium‐aluminum synthetic garnets, obtained by sol‐gel method
Authors: Carda J. , Tena M. A. , Monros G. , Esteve V. , Reventos M. M. , Amigo J. M. 
Published: January 2007

AbstractA series of synthetic garnets solid solutions is compositions between Y3Al2Al3O12 (Y‐Al garnet) (YAG) and Ca3Cr2Si3O12 (uvarovite) was synthesized using the sol‐gel method. The expected general formula is (CaxY1‐x)3 (CrxAl1‐x)2 (SixAl1‐x)3O12 where x = 0 to x = 1.The cation distribution in dodecahedral, octahedral and tetrahedral sites and bond distances in these synthetic garnets were determined using the Rietveld method. It shows the incomplete substitution in small sites. The smaller site the smaller substitution there is.
The preparation of calcium oxalate dihydrate crystals
Authors: Doherty W. O. S. , Crees O. L. , Senogles E. 
Published: January 2007

AbstractTwo simple related methods for exclusively preparing well‐developed tetragonal bipyramidal crystals of calcium oxalate dihydrate at moderate supersaturations and at ambient temperature are reported. These crystals have an average length of 5.7–7.2 μm and are easy to wash and filter. One of the methods is suitable for studies of the kinetics of spontaneous precipitation and crystal morphology of the oxalate in the presence and absence of additives. A tentative mechanism is given to account for the sole formation of this particular hydrate.At 70 °C a mixture of the monohydrate and dihydrate phase were formed with various crystal shapes and sizes. These phases were also identified in the presence of sucrose at this temperature, although some of the crystals contained tetragonal habit as obtained at ambient temperature.
The crystal and molecular structure of three homologue 1,4‐dialkanoyloxy‐biphenyls (SYM‐n)
Authors: Thyen W. , Zugenmaier P. 
Published: January 2007

AbstractThe three homologue compounds with the general formula CnH2n+1COOC6H4C6H4OOCCnH2n+1 (SYM‐n) crystallize in the following space groups: SYM‐1: triclinic, P1, a = 7.400(6), b = 9.227(3), c = 10.579(3) Å, α = 85.97(3), β = 89.09(3), γ = 71.47(3)°; SYM‐2; monoclinic, P21/c, a = 11.712(7), b = 5.648(1), c = 12.408(6), Å, β = 103.84(3)°; SYM‐5: triclinic, P1, a = 5.505(4), b = 8.342(8), c = 24.79(2) Å, α = 86.67(3), β = 85.45(6), γ = 71.74(7)°.The structures have been solved by direct methods and refined to R = 0.075, 0.061 and 0.053, respectively. The packing arrangements show a layer‐like structure. The layers are almost separated for SYM‐1 as well as for SYM‐2 and interdigitated for the structure of SYM‐5.
Elastic properties of the pseudocubic perovskite (CsCd(NO2)3
Authors: Haussühl S. 
Published: January 2007

AbstractMultidomain crystals of CsCd(No2)3 grown from aqueous solutions at about 310 K exhibit a quasi‐cubic symmetry in their thermal expansion, elastic and thermoelastic properties. The elastic constants of the low‐temperature multidomain state resemble the behaviour of stable cubic perovskites almost quantitatively. This suggests that the trigonal low‐temperature phase of CsCd(NO2)3 possesses a quasi‐cubic symmetry. The transition from the trigonal low‐temperature phase into the cubic high‐temperature phase at about 464 K is accompanied by a small deformation of about 10−4 and a lambda‐type variation of the thermal expansion.
Computer‐aided evaluation of kossel patterns obtained from quasicrystals
Authors: Weber S. , Schetelich Ch. , Geist V. 
Published: January 2007

AbstractFor the evaluation of Kossel experiments on quasicrystals such as the decagonal phase of AlCoNi or AlCoCuSi a computer program called KOQUA has been written, which allows to simulate Kossel patterns of two‐ and three‐dimensional quasicrystals as well as of every conventional crystal system. In some examples the application of the program is demonstrated.