bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal Structure and Thermal Phase Behaviour of 2,3‐Dicyano‐4‐n‐hexyloxyphenyl‐trans‐4‐n‐heptyleyelohexanoate
Authors: Hartung H. , Baumeister U. , Jaskólski M. , Mädicke A. , Wiegeleben A. 
Published: January 2007

AbstractThe title compound with the formula C7H15C6H10COOC6H2(CN)2OC6H13 (DHPHC) crystallizes in the monoclinic space group P 21/n with a = 5.633(1), b = 14.254(1), c = 33.435(7) Å, β = 91.56(2)°, and four molecules per unit cell. The structure has been solved by direct methods and refined to R = 0.082.The DHPHC molecules adopt a banana‐shaped but considerably stretched form and show a parallel arrangement of their long axes in the crystal lattice.The phase transitions of DHPHC have been investigated by DSC and thermal microscopy. The compound shows a rather complicated melting behaviour and forms two solid phases and a monotropic smectic A phase.
EDA Complexes in Liquid Crystalline Mixed Phases of Novel Compounds with Lateral Dicyanoethenyl Substituents
Authors: Weissflog W. , Pelzi G. , Demus D. 
Published: January 2007

AbstractWe synthesized each four members of the new series magnified image All compounds are nematic. The dicyanoethenyl derivatives possess strong elecgtron acceptor properties. This is demonstrated by EDA complex formation in two binary systems in which induced smectic phases are lacking.
The Influence of the Purity and Thickness of Niobium Foils on its Mechanical Properties
Authors: Savitsky E. M. , Efimov Yu. V. , Galperovich D. Ja. , Korzhakova T. V. , Rjabtzev L. A. , Shapovalov Yu. P. , Brovko A. P. 
Published: January 2007

AbstractThe content of contaminants, microstructures, surface condition, electrical resistivity and mechanical properties of niobium foils and bands (13–1000 μm thick) after cold working (90–99.9%), surface etching and heat treatment under vacuum (0.001 Pa at 700–1200 °C for 1–5 hrs) are studied. The effect of the previous working and different environmental conditions including initial and acquired surface contamination with oxygen, carbon, nitrogen and iron increases noticeably with the rise of the working degree and decrease of the foil thickness. The mechanical properties of foils and bands (≧ 100 μm) practically don't differ from massive standard samples. At the foil thickness of ≦ 40 μm the dimensional effects and the influence of the surface layer are especially noticeably. The optimal combination of the whole complex of surface and volume properties at the minimum dimensional effects is observed on the 50 μm thick foil. The improvement of foil properties can be achieved due to etching its surface layer up to the depth not less than 4 μm (on each side) after the cold working and following annealing at 1000–1100 °C (1–3 hrs).
Physico‐Chemical Properties of Kutch Bentonite
Authors: Takoo R. K. , Patel B. R. 
Published: January 2007

AbstractA report about the location and estimated amount of bentonite deposits in the Kutch district of Gujarat State, India is presented. Physioc‐chemical analysis reveals that Kutch bentonite is a sodium‐predominant variety and X‐ray diffraction data shows that it consists mainly of montmorillonite and beidellite and contains minor amounts of vermiculite. It is suggested that quality‐wise Kutch bentonite possesses all the properties equivalent to Wyoming bentonite.
Mechanism of Various Growth Morphologies of Kutch Quartz Crystals
Authors: Takoo R. K. 
Published: January 2007

AbstractLocations and estimated amounts of deposits of quartz crystals found in the Kutch district of Gujarat State, India are given. A report about various morphologies of these crystals in geodes is presented. Influence of supersaturation on the mechanism of formation of the initial, intermediate and final growth morphologies has been assessed. It is suggested that the changing growth morphology is a function of supersaturation value. Trapezium‐shaped and semi‐circular hillocks observed on the prism faces are described and discussed. It is proposed that these hillocks develop and grow in a sequential manner and like crystals have initially triangular form.
DC Electroluminescence in (ZnS, ZnO): Cu, Cl Electroluminors
Authors: Bhushan S. , Diwan Deepti 
Published: January 2007

AbstractSome interesting oberservations on the DC electroluminescence of (ZnS, ZnO):Cu, Cl electroluminors are reported. A burst of emission is observed at the time of switching on (also at switching off) the field which very slowly decays to a saturation value. The time for saturated emission decreases with increasing temperature. The emission colours of bursts and the saturated light are different. The intensities of the bursts are dependent upon the polarity of the electrodes and the temperature. Possible explanations to these effects are proposed.
Growth and Morphological Studies of Anhydrous Diglycine Sulfate Single Crystals
Authors: Pandya G. R. , Vyas D. D. 
Published: January 2007

AbstractDiglycine sulfate single crystals are grown from aqueous solution by evaporation method. The effect of growth conditions are studied with respect to the perfection and morphology of the crystals. The seed history, growth temperature and pH of the solution are found to bear pronounced effects. The results are reported in the present paper.
Glow Curves of Thermally Pretreated KCl:Mn2+ Crystals
Authors: Sayanna R. , Reddy K. Narasimha 
Published: January 2007

AbstractThermoluminescence studies of KCl crystals doped with 0.5 mole% of Manganese both in “as grown” state and after quenching them from various elevated temperatures indicate that the position of the glow peaks is found to depend upon the state of dispersion of impurity. In quenched crystals two additional peaks one around 130 and other around 215°C are observed. Dipoles near dislocations are suggested to be responsible for 130°C peak and 215°C peak to a complex formed by the associated of one or more Mn2+ ions with a single vacancy or an aggregate of vacancies, the complex being situation in the dislocation region.
Crystallisation Mechanism in Gradient Temperature Zone Melting
Authors: Peev N. S. 
Published: January 2007

AbstractTheory of zone recrystallization in the framwork of already known models of normal crystal growth, growth by screw dislocations and by two‐dimensional nucleation is discussed. By mathematical treatment, different from Tillers approach, analytical expressions for supersaturation at the crystallisation interface, for superheating at the dissolution interface, growth rate and some other parameters have been obtained for both cases of normal and screw dislocations growth. It is possible to determine the growth mechanism.
Surface Roughening and Surface Self‐diffusion. A Monte Carlo Simulation
Authors: Nenow D. , Trayanov A. , Paunov M. 
Published: January 2007

AbstractA model for atom diffusion on surface is proposed, the energy barrier for surface self‐diffusion as well as the barrier for diffusion along surface steps being considered. Using a Monte Carlo method, the equilibrium structure of crystal surface is obtained and its effect on the surface self‐diffusion is studied. The mass transfer surface self‐diffusivity Ds and the mean diffusion distance λ are calculated for different temperatures T. A nonlinear Arrhenius plot (log D vs l/T) is obtained. The maximal deviation from linearity occurs at roughening temperature.
Colour Centre in Nd3+‐doped Yttrium Aluminates
Authors: Kvapil Jiřì , Kvapil Jos. , Perner B. , Mánek B. , Blažek K. 
Published: January 2007

AbstractSpectroscopic and laser properties of YAG:Nd and YAP:Nd grown from the nonstoichiometric melts or those containing Mo and Fe impurity were compared. YAG:Nd grown from the melt with surplus of Y2O3 and annealed in H2 at ∼ 1400 °C have an increased laser performance. Mo admixture in hydrogen annealed YAP:Nd laser crystals suppresses effectively the detrimental action of iron impurity.
Quantum‐chemical Approach to the Dependence of Oxygen Charge on Bond Angle in SiO2
Authors: Pietsch U. , Hübner K. 
Published: January 2007

AbstractA recently published review on the effective oxygen charge in SiO2 and its dependence on the bond angle of oxygen has shown that, as a rule, solid‐state theoretical calculations lead to the conclusion that the oxygen charge increases with increasing bond angle, whereas quantum‐chemical calculations for limited clusters yield an opposite result, i.e. a decrease of the oxygen charge with increasing oxygen angle. In the present paper it is shown that also a quantum‐chemical approach to the problem, namely a molecular‐orbital calculation for an SiOSi bridge, reveals an increase of the charge of oxygen with its bonding angle, which is, however, relatively weak.
Solvus of KCI:Pb2+ Solid Solution from Flotation Measurements of Single Crystal Density
Authors: Dudnikova V. B. , Urusov V. S. 
Published: January 2007

AbstractThe solvus of KCl:Pb2+ is found in the concentration range from 1.6 × 10−2 to 8 × 10−2 mol.% at temperatures ranging from 450 to 250 °C. The decomposition of the solid solution after various regimes of heat treatment is judged by a change in the crystal density determined by the flotation technique.
Etch Pattern of Gel‐grown Single Crystal of Ammonium Tartrate
Authors: Saraf A. G. , Saraf K. B. , Wani P. A. , Bhoraskar  
Published: January 2007

AbstractUsing optical techniques, a study was carried out of the etch patterns produced, by diluted oxalic acid and sodium hydroxide solution, at 30°C. Point bottomed and flat bottomed rectangular etch pits nucleated at the sites of dislocations parallel to ‘C’ axis of the crystal are observed. Mostly they are isolated, and randomly distributed. Further, on prolonged etching they penetrate deeper and their eccentricity can be attributed to the inclined nature of dislocations.
Effect of Growth Parameters on Spatial Pattern Formation of Cadmium Hydroxide in Agar Gel
Authors: Palaniandavar N. , Gnanam F. D. , Ramasamy P. 
Published: January 2007

AbstractThe interrelated effects of growth parameters on spatial pattern formation of cadmium hydroxide in agar gel medium have been investigated. The main parameters are concentration of electrolytes,pH of the medium, density of the gel, the concentration of parasitic electrolyte and the concentration of additives. The pattern formation is explained on the basis of electrical double layer theory coupled with diffusion. Using Shinohara's revised coagulation concept, the flocculation value is calculated. With suitable combinations of parameter values, dendritic growth and spherulitic growth of cadmium hydroxide crystals have been observed.
Information on the Operating Mode of Decomposition during the Cooling of an Al‐10 at.% Zn Alloy to Various Tq
Authors: Wendrock G. , Löffler H. , Nüssler E. , Reimann G. 
Published: January 2007

AbstractInformation about the operating mode of decomposition during cooling to various Tq were gained by SAXS method. After reaching the Tq wanted the samples were quenched into water of RT and the SAXS intensity curves were measured at RT. Strong evidence was found that below about 175 °C the decomposition starts in this alloy with the nucleation and growth of Guinier‐Preston zones. As proved by other authors, 175 °C is the upper limit temperature Trhm for the onset of the rapid homogeneous nucleation of precipitates.
Morphology and Structure of Thermally Induced Microdefects in High‐Temperature Treated Czochralski‐Silicon
Authors: Reiche M. , Nitzsche W. 
Published: January 2007

AbstractThe morphology and structure of amorphous precipitates grown by thermal annealing in the temperature range from 1100 °C to 1200 °C are investigated by means of highvoltage electron microscopy. It is shown that there exist some characteristic morphological types which are equivalent to the equilibrium forms of the cubic diamond structure itself or which can be derived from these. For the growth process an oxygen diffusion‐controlled mechanism is deduced. Structural aspects are discussed on the basis of this mechanism.
Dislocation Photoconduction and Related Dislocation Memory Effects in KCl Crystals
Authors: Turchányi G. 
Published: January 2007

AbstractTwo types of memory phenomena are discussed, both related to dislocation photoconduction of highly pure and coloured KCl crystals, using the combination of Lyman‐ and F‐illuminations. A very simplified explanation of the dislocation memory effects is given taking into consideration possible changes in the direction of the photocurrents. Some considerations may be of interest for the explanation of photoplastic effects.
Optical Topographic Studies on the Natural Iron Pyrite (FeS2) Crystals
Authors: Prasad P. B. V. 
Published: January 2007

AbstractStudies on the microtopographical features present on the natural iron disulphide crystals are carried out. Presence of striations, propogating in directions parallel to one of the crystal edges, is noted. Detailed studies reveal that the edges of highly elongated layers, covering the entire crystal face, appear as striations. This aspect is further probed and it is found that the crystals grow by two dimensional nucleation. The features resulting from the interaction of impurity clusters with surface process are studied to determine the nature of the surface process; the features are interpreted as due to growth and not due to dissolution.
Precipitation of Alkaline‐Earth Metal Silicate Hydrates from Aqueous Solution: Ionic Equilibria, Crystalline Phases and Precipitation Mechanisms
Authors: Packter A. 
Published: January 2007

AbstractThe precipitations of magnesium, calcium, strontium, barium and zinc silicate hydrates from aqueous solutions and suspensions at ambient temperature to 200 °C are surveyed. The relevant ionic equilibria (silicate and polysilicate anion formation, hydroxocation formation, alkaline‐earth metal silicate hydrate and hydroxide precipitation from supersaturated solution) that may influence these precipitations are examined. ‐ The microcrystalline and crystalline phases precipitated in systems of different cation/silicate compositions and temperatures are tabulated. Precipitation mechanisms are analysed.
Epitaxial Growth of Silver Bromide on Mica from the Melt
Authors: Fischbach Harald 
Published: January 2007

AbstractIt is shown that it is possible to grow silver bromide crystals with definite crystallographic orientation by solidification of liquid silver bromide between mica and quartz plates by cooling the mica side. The orientation is (111). The maximum dimensions were 15mm × 15 mm × 1 mm. The surface is investigated by electron reflection (RHEED). The crystals have a smooth surface and can be used for optical application without surface reconstruction.
Hydrothermal Synthesis of Zeolite Crystals Using Natural Scolecite
Authors: Joshi M. S. , Choudhari A. L. , Kanitkar R. G. 
Published: January 2007

AbstractNatural scolecite is converted into analcime type zeolite by hydrothemal method at 180 °C at autogeneous pressure for 24 to 160 hours growth runs. Mordenite is detected in the final product. Cube and spheroid crystals of the products are illustrated and described. Crystals synthesized are characterized by X‐ray diffraction, infrared spectroscopy EDAX and scanning electron microscopy. Particle size is estimated as 20–60 microns, induction period for nucleation as 12 hrs, and lattice parameter of cube crystals as 13.70 Å. Mechanism of growth, influence of anions and duration of growth etc. are discussed. It is established that the crystals grow in the system Na2OAl2O3SiO2H2O.
Crystal Structure Phase Transitions in the Perovskites A(Cu1−xMnx)Mn4O12(A = Na+, Ca2+, Y3+, La3+)
Authors: Troyanchuk I. O. , Balyko L. V. , Bashkirov L. A. 
Published: January 2007

AbstractX‐Ray diffraction and neutronographical studies on the crystal structure of the perovskitelike compounds A(Cu1−xMnx)Mn4O12 have been undertaken. It has been shown that the samples with 50% of Mn3+ in the octahedral sites have a cubic unit cell, while the samples with higher Mn3+ composition may have a monoclinic or rhombohedral unit cell. The temperature increase raises the symmetry to the cubic one. The concentration ranges with different symmetry type have been determined. The lowering of the symmetry of the unit cell is due to the cooperative Jahn‐Teller effect.
Observation of Intermediate Smectic A Structure at the Phase Transition Nematic‐Smectic C in 4,4′‐di‐n‐Heptyloxyazoxybenzene
Authors: Simova P. , Petrov M. 
Published: January 2007

AbstractUsing different boundary conditions in thin film of 4,4′‐di‐n‐heptyloxyazoxy benzene and studying the microscopic textures as well as the depolarized Rayleigh light scattering, an intermediate smectic A‐like state during the nematic‐smectic C phase transition was observed.
The Interface Unstability of the Solubility Boundary in the Gradient Temperature Zone Melting Method
Authors: Peev N. S. 
Published: January 2007

AbstractIn the present work the interface unstability of the solubility boundary in the gradient temperature zone melting method is considered for the case of large breach amplitude and great wave length. The critical value of the amplitude at which the breach begins to form as a drop in front of the solubility boundary is determined. It is assumed that the crystallization and the solubility processes are accomplished by the dislocational and normal mechanisms.
Optical Properties of CuInSe2 Single Crystals Grown by the Vertical Bridgman Technique
Authors: Neumann H. , Hörig W. , Tomlinson R. D. , Avgerinos N. 
Published: January 2007

AbstractThe optical absorption near the fundamental edge of n‐type CuInSe2 single crystals was studied for samples having different impurity concentrations. It is found that with increasing impurity concentration the gap energy decreases whilst the tail absorption below the edge and its characteristic energy increase. It is concluded that band‐gap narrowing due to high ionized impurity concentrations plays an important role in CuInSe2 single crystals.
Studies on the Effect of Unsaturated Homologues on the Crystallization of Stearic Acid
Authors: Prasad P. B. V. , Sato K. 
Published: January 2007

AbstractThe unsaturated fatty acids play decisive role in the activity of biological membranes. The interaction between saturated and unsaturated fatty acids during the condensation process is therefore of great importance. Studies on the crystallization of stearic acid (a typical saturated acid), in presence of oleic acid and linoleic acid (typical unsaturated acids), were carried out to determine the extent of interaction. Results indicated that interaction between saturated and unsaturated molecules is almost absent. It can be derived from the findings that these molecules might participate in biological or biochemical processes, as if they are entirely different types of molecules.
Structural Studies on Ni75(SnSi)25 and Ni75(SnBi)25 Alloys
Authors: Shadangi S. K. , Singh M. , Panda S. C. , Bhan S. 
Published: January 2007

AbstractTernary alloys on the quasi‐binary system Ni3Sn(r) in equilibrium condition. It has been observed that these phases undergo transformations at high temperatures but upto 500 °C room temperature modifications are stable. The two phases do not have any appreciable solid solubility in either of them. The phase Ni3Si(r) crystallizes in to Cu3Au (Li2) structure where as Ni3Sn(r) is based on c.p.h. structure with a = 5.305 A°, c = 4.254 A°. No new ternary phase has been detected in Ni3SnNi3Si section.The investigated alloys of the NiSnBi system contain 75 at.% Ni. All the ternary alloys show simultaneous occurrence of three phases, namely Ni3Sn(r), NiBi and Ni(Sn) in equilibrium state. The phase NiBi has NiAs(B8) type of structure. Due to non‐existence of isostructural phases in the two binary systems (NiSn and NiBi), single solid solution phases are not formed. Widely differing atomic sizes of nickel and bismuth atoms restrict the formation of solid solution of bismuth in nickel in contrast to Ni(Sn) where atomic size factor is favourable.
Defects in LEC‐grown Indium Phosphide Crystals Doped with Tin
Authors: Wagner G. , Gottschalch V. 
Published: January 2007

AbstractCrystalline defects in Sn‐doped LEC indium phosphide have been revealed by chemical etching and analyzed by TEM. Grown‐in dislocations, various kinds of defect clusters and colonies of microdefects were found. The symmetrical defect clusters are shown to equate mostly with larger dislocation loops exhibiting shear components and/or other dislocation arrangements generated by a stress source which is positioned in the centre of the dislocation cluster. Those centres are often formed by a plate‐like agglomeration composited of tiny inclusions and very small faulted dislocation loops. Such planarly arranged accumulations of microdefects lie on {111} planes. The direct vicinity of single threading grown‐in dislocations is always enriched with tiny perfect dislocation loops and precipitates. Additionally, very large isolated interstitial‐type perfect dislocation loops with b = a0/2 〈110〉 have been found by TEM experiments. Mostly, the {110} habit plane of such loops is decorated with an high number of small dislocation loops and precipitates as a consequence of dislocation climb.
Dielectric and Electrical Properties of InSe Films
Authors: Rao S. Ramchandar , Pratap K. J. , Babu V. Hari 
Published: January 2007

AbstractThe dielectric and electrical properties of sandwiched AlInSeAl structures of different thicknesses are investigated. For all the thicknesses the capacitance and tan δ decrease with increase in frequency. The I‐V characteristics of Al‐InSe‐Al structures have been studied for different thicknesses. These curves exhibit three regions ohmic, non‐ohmic and breakdown regions. Optical micrographs of breakdown patterns at different stages have been taken and the results are discussed.
Influence of Predeposition on the Properties of GaN
Authors: Franzheld R. , Seifert W. , Butter E. 
Published: January 2007

AbstractGrowth experiments with GaN in the system Ga/HCl/NH3/He or H2 were carried out in a reactor with two deposition zones. The extent of the reaction in the first zone, called the predeposition zone, is controlled by the NH3 flow rate. In the second zone GaN is deposited epitaxially onto sapphire substrates. The variation of the carrier concentration of these epilayers indicates the dominating effect of impurities especially oxygen in opposition to the widely accepted vacancy model. Due to the high incorporation ratio of donor impurities into the solid a predeposition reduces the impurity content in the vapour phase. A reduction of the free carrier concentration in the epitaxial layers could be achieved. Different behaviour in the two carrier gas systems could be established.
The Smetic Polymorphism and the Phase Transitions in the Liquid Crystal 4, n‐Hexyloxyphenyl‐4, n′‐Decyloxybenzoate
Authors: Petrov M. , Simova P. 
Published: January 2007

AbstractThree different methods — microscopical, depolarized light scattering and conoscopic have been used for the investigation of the polymorphism of 4, n‐hexyloxyphenyl‐4, n′‐decyloxybenzoate (HOPDOB) at homeotropic orientation. A new textural transition is registered during cooling in smectic C phase connected with a change in the tilt (ω) and azimuthal (φ) angles of the molecular director. At cooling we found smectic E phase and by the conoscopic method we determined this phase as tilted smectic type (Et) with 24° tilt angle. It is also found that B phase is a normal type smectic liquid crystal — BN.
A Pragmatic Model for the Simulation of Self‐induced Striations in Quartz Crystals
Authors: Bernhardt Hj. 
Published: January 2007

AbstractA mechanism is investigated which might lead to fluctuations in the growth of quartz crystals due to the periodic incorporation of impurities. The model ought to be applicable also to the incorporation of stoichiometric partners during the growth of complicated crystals from non‐stoichiometric melts. The processes have been simulated with help of an equivalent circuit experimentally and by computation. Some typical cases are presented in the paper.