bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of chemical composition on structural and selected physical properties of natural natrolites
Authors: Pechar František
Published: January 2007

The relation among changes in contents of Si and Al atoms, molecules of water and symmetry of the unit cell of crystal natural Natrolites was determined.

It was found that with the change of the relations Si/Al and Na/H2O the symmetry of the Natrolite structure changes from Fdd2 through Fd(Cc) to F4d2 (I4d2). With the change in the distribution of these atoms in this structural position also changes of optical (refractive index, IR spectra) and thermodynamic (Sconf) properties and thermal stability are closely connected.
Colour bands of oxidized nickel dioximes
Authors: Oza A. T.
Published: January 2007

Strong colour bands are observed in the mull absorption spectra of the oxidized nickel chain dioximes bis (1,2‐benzoquinonedioximato) Ni.I0.5 and bis (diphenylglyoximato) NiIIIBr in the long wavelength region of the optical spectrum which are ascribed to the reduced metal‐metal distance due to oxidation. The uv‐visible spectra of bis (dimethylglyoximato) NiII and bis (diphenylglyoximato) NiII have also been studied in the present comparative study. All the bands in the uv‐visible range are assigned. The transitions and the effects of partial oxidation on the electronic transitions are discussed.
Effect of polarity of smectic Ad molecules on the induction of the nematic phase in binary mixtures of smectics A1 and Ad
Authors: Dąbrowski R. , Czupryński K.
Published: January 2007

The phase diagrams are determined of binary mixtures composed of 4‐n‐alkylbiphenylates 4‐cyanobiphenyl (n‐CBB)‐smectics A1, for n < 8 and esters of 4‐(trans‐4′‐n‐alkylcyclohexyl)benzoic acid (10CPCHB, 10NPCHB, 10FOPCHB)‐smectics Ad.

The effect is studied of the smectic layer spacing ratio and polarity of the components on the induction of the nematic phase in the tested series of compounds. The virtual NSAd phase transition points in series n‐CBB are estimated and the effect is discussed of the stability of the smectic phase and polarity of the molecules of the mixture components on the width and position of the nematic gap.
Investigations for the improvement of the radial doping homogeneity of dislocation‐free floating zone silicon crystals
Authors: Schröder W. , Rost H.‐J. , Wolf E.
Published: January 2007

In order to improve the doping inhomogeneities of dislocation free FZ Silicon crystals with diameters ≧ 75 mm investigations were carried out to influence the shape and curvature of the crystallization interface during the crucible‐free floating zone crystal growth process. In this works shapes and geometries of the applied melting inductors and the relative positions of these inductors to the seed axis were examined concerning the values of radial macroscopic and microscopic doping inhomogeneities in dependence on other growth parameters, for instance crystal rotation rate. The application of eccentric inductor‐seed positions effects a decreasing “bending value” of the crystallization interface, that means an improvement of the macroscopic radial doping inhomogeneity with crystal rotation rate in the range between 4 and 8 min−1.
Dielectric behaviour of TGS crystals poled by doping on repeated temperature cycling
Authors: Lhotská V. , Holakovský J. , Fousek J. , Březina B.
Published: January 2007

Data characterizing the stability of basic dielectric properties against thermal treatement are presented for crystals of TGS and deuterated TGS doped with alanine or bivalent platinum. Complex permittivity and over‐all polarization have been measured during a heating‐cooling cycle. In alanine doped crystals the heating and cooling curves are perfectly reproducible. In Pt‐doped samples the reproducibility is worse, for pure TGS the properties on cooling are strongly influenced by domain effects. These data made it possible to estimate the change of the figures of merit for pyroelectric ir detectors due to transient heating.
A systematic search of the dopants of calcium sulphide and their effect on the TL spectra above room temperature
Authors: Rennie J. , Sweet M. A. S.
Published: January 2007

Results on the thermoluminescence following incorporation of a wide range of dopant materials in calcium sulphide are reported. These results are compared with those previously reported in the literature. Factors such as fluxes and preparation technique are varied to determine their effect on the TL spectra. Conclusions regarding the possible source of the traps causing the TL in CaS are drawn with the evidence suggesting natural defects as the source of the traps; the added dopant impurities having only a secondary effect on the thermoluminescence peak temperatures.
Optimization of the cascade crystallizers
Authors: Belcu M. , Pincovschi E.
Published: January 2007

For the cascade crystallization process a set of technological optimization conditions was established. The possibility of succesful application of proposed optimization conditions was pointed out by comparison with a mathematical model of Na2SO4 · 10 H2O crystallization in multichamber crystallizer presented in the literature. The method has a general applicability and can be used for the optimization of any cascade‐linked system, provided that the mathematical model was detailed enough to permit the operation of numerical derivation.
Entropy production in steady‐state eutectic growth
Authors: Wolczyński Waldemar
Published: January 2007

A theoretical analysis of models for regular eutectic growth is presented. The diffusion model (practically, a relationship between interlamellar spacing, λ, and growth rate, v, proposed in JACKSON and HUNT'S theory) is localized at the paraboloid of entropy production for the process under investigation. As this paraboloid depends on the temperature and concentration gradients it is concluded that a new model which should consider both heat transfer and diffusion in the steady‐state eutectic growth is to be introduced using the substantiated criterion of minimum entropy production. In this way, it is possible to obtain an equation of the f(λ, v, δT/δx) = 0 type.
Influence of the structure of InP thin films on electron energy loss spectra
Authors: Gründler R. , Boudriot H. , Deus K. , Sckneider H. A. , Stöckert T.
Published: January 2007

Electron energy loss measurements were carried out on single crystalline, polycrystalline, and amorphous InP thin films. Plasmon data and structures of − Im ε−1 are discussed in dependence on degree of crystallinity.
The influence of γ‐irradiation on ferroelectric and polarization properties of TGS crystals
Authors: Tsedrik M. S. , Margolin L. N. , Gontarev V. F. , Misko A. S.
Published: January 2007

The experimental investigation of pyroelectric and polarization properties of TGS crystals was made. TGS crystals were grown under constant growth conditions (temperature and supersaturation of the solution) and γ‐irradiated in a wide range of irradiation. The influence of γ‐irradiation on the quality parameter M2 of crystals, on the form of hysteresis loops, on size of spontaneous polarization and shifting field was ascertained.
Electrooptic properties of polycrystalline SnSe thin films
Authors: Bhatt V. P. , Gireesan K. , Desai C. F.
Published: January 2007

It is observed from the studies of electrical resistivity of films of SnSe of different thicknesses and substrate temperatures that resistivity decreases with increase in thickness and substrate temperature. The study of variation in band gap with thickness shows a linear relationship between band gap and 1/t2. Finally, band gap – substrate temperature studies show that the band gap increases with substrate temperature.
Infrared optical properties of (CuGe2P3)1−x(6 Ge)x solid solutions
Authors: Riede V. , Sharif N. , Neumann H. , Sobotta H. , Omar M. S.
Published: January 2007

Infrared reflectivity spectra of (CuGe2P3)1−x(6 Ge)x mixed crystals with compositions in the range x = 0.07–0.33 are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. An analysis of the spectra reveals six vibrational modes. The composition dependence of the mode frequencies and of the free carrier concentration and mobility is given and compared with infrared optical data for CuGe2P3.
Memory‐switching effect in single crystals of thallium selenide
Authors: Hussein S. A.
Published: January 2007

It has been found that thallium selenide single crystals exhibit bistable or memory switching. The specimen under test showed threshold switching with critical field of the switching being ∼ 103 V/cm at room temperature. Memory switching effect measurements were performed with single crystals of p–TlSe. The results strongly indicated that the phenomenon in our sample is very sensitive to temperature, light intensity and sample thickness. Memory state persists if the current is decreased slowly to its zero value. However, if current was forced to decay suddenly, the specimen returned to the high resistance state. The current‐voltage characteristics is symmetrical with respect to the reverse of the applied voltage and current. The switching parameters were checked under the influence of different factors of the ambient condition. An analysis of the results was done.
Preparation and properties of ultratransparent NaCl single crystals
Authors: Nistor S. V. , Mateescu C. D. , Nistor L. C. , Teodorescu V. S.
Published: January 2007

The preparation of up to 100 mm diameter single crystalline ingots of ultratransparent NaCl by injecting the reactive atmosphere is reported. The resulting material exhibits high optical quality and bulk absorption coefficient at 10.6 μm of 0.91 × 10−3 cm−1, close to the intrinsic value, which makes it suitable for transmissive components in high‐power CO2 lasers.
Rietveld refinement of Y2O3 using the Pearson VII profile shape function
Authors: Smrčok L.
Published: January 2007

Very good agreement between the observed and the calculated intensities was obtained using the Pearson VII profile shape function. The variable exponent m could be refined only in the damped iterations involving exclusively the profile parameters. Simultaneous refinement of the m with the positional and/or thermal parameters has led to large oscillations of the shifts of almost all parameters. Precision of the refined atomic coordinates is better than those from previously published Rietveld refinement and is comparable with single crystal results. The degree of serial correlation in residuals has been determined by the use of the Durbin‐Watson d statistic. Normal probability plot based on δRi has been almost linear with the slope greater than one. The weighting scheme with wi = 1/yoi has proved to be good first approximation.
Etch features in bismuth germanate (Bi4Ge3O12) single crystal
Authors: Péter Á. , Polgár K. , Contreras L. , Dieguez E.
Published: January 2007

The three component mixture of HCl: HNO3: CH3COOH in the volumetric proportion of 3: 1: 4 was found to be a satisfactory etchant for various surfaces of Bi4Ge3O12. The correlation between etch pits and dislocations was established by means of repeated etching and optical observations.
Optical absorption behaviour of magnesium‐implanted GaAs
Authors: Hörig W. , Bouamama Kh. , Neumann H. , Nobes M. J.
Published: January 2007

Optical absorption spectra of magnesium implanted GaAs single crystals are measured in the photon energy range below the fundamental absorption edge. It is found that the absorption coefficient increases with increasing fluence up to a saturation value of about 5 · 104 4 cm−1 at 1.36 eV. The results are compared with optical measurements on GaAs single crystals implanted with other ions.
Temperature dependences of the electrical conductivity and hall coefficient of indium telluride single crystals
Authors: Hussein S. A.
Published: January 2007

Conductivity type, carrier concentration and carrier mobility of InTe samples grown by Bridgmann technique were determined by the Hall effect and electrical conductivity measurements. The study was performed in the temperature range 150–480 K. Two samples with different growth rate were used in the investigation. The samples under test were P‐type conducting, in accordance with previous measurements of undoped material. The Hall coefficient was found to be isotropic yielding room temperature hole concentration in the range 1015 – 1016 cm−3. The hole mobilities of InTe samples were in the range 1.17 × 103 – 2.06 × 103 cm2/V · sec at room temperature. The band – gap of InTe determined from Hall coefficient studies has been obtained equal to 0.34 ev. The scattering mechanism was checked, and the electrical properties were found to be sensitive to the crystal growth rate.
A nematic two frequency adressing mixture with extremely low isotropy frequencies
Authors: Stettin H. , Kresse H. , Haas S. , Schäfer W. , Heidenreich G. , Zaschke H.
Published: January 2007

New liquid crystalline substances with four benzene rings have been synthesized. A nematic two frequency mixture containing some of these compounds was produced and dielectrically as well as electrooptically investigated. With dielectric measurements a very low frequent and distributed relaxation mechanism at room temperature could be estimated (fR = 0.0565 kHz, h = 0.25 at 294.2 K). Although new substances have been used the switching behaviour in a TN cell showed disturbances as on an earlier developed two frequency mixture.
Crystal and molecular structure of 1‐(p‐nitrophenyl)‐2‐acetylamino‐3‐brom‐propen‐2‐on‐1, C11H9BrN2O4
Authors: Ramm M. , Kuban R.‐J. , Schulz B.
Published: January 2007

Mr= 313.11, orthorhombic space group Pbca,a= 8.165(1),b= 9.491(2),c= 32.207(5) ÅV= 2496(1) Å3,DX= 1.667 Mgm−3,Z= 8, F(000) = 1248, λ(MoKα) = 0.71069 Å, μ = 32.7 mm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factorR= 0.065. Positions of hydrogen atoms were calculated.

The structure determined by x‐ray analysis confirms the chemical results.
Synthesis and characterization of ferroelectric magnesium hydrogen phosphate single crystals
Authors: Desai C. C. , Patel K. N.
Published: January 2007

Ferroelectric Magnesium Hydrogen Phosphate MgHPO4 (MHP) single crystals are grown by slow diffusion of magnesium chloride in sodium metasilicate gels impregnated with orthophosphoric acid. Bright and transparent prismatic, tabular, and isometric habit MHP crystals upto 3 × 2 × 1 mm3 are obtained. Results of chemical, X‐ray diffraction, EDAX, microhardness and magnetic analysis are reported. The average etch pit density is determined by chemical etching to be 7 × 103 cm−2. Microtopographic investigations revealed the mechanism of crystal growth.
Deformation behaviour of single crystals of GaP in uniaxial compression
Authors: Paufler P. , Retzlaff U.
Published: January 2007

LEC n‐GaP:S single crystals were deformed in uniaxial compression parallel [321] and [110] direction. Plastic deformation by (111) slip has been observed between 511 °C and 717 °C. Indications for (111) twinning were obtained. Yield stress exhibits activation enthalpies U = Q(m + 2) and stress exponents m of U321 = (0.54 ± 0.05) eV, U110 = = (0.46 ± 0.05) eV, m = 1.1 ± 0.2 and m = 3 ± 1, respectively.
Oxidation of tetracyanonickellate (II) in the presence of organic cation
Authors: Oza A. T.
Published: January 2007

A new material (TMPD)2Ni(CN)4I0.5 · H2O has been prepared (TMPD = N,N,N′,N′‐tetramethyl‐p‐phenylenediamine). The solution and mull absorption spectra in the infrared range indicate the presence of the redox process TMPD+ ⇌ TMPD2+ and tetracyanonickellate (IV) units.
Density studies across smectic‐smectic transitions in 70.6 and 80.10
Authors: Rao P. Bhaskara , Rao N. V. S. , Pisipati V. G. K. M. , Saran D.
Published: January 2007

The temperature dependence of density in N(p‐n‐heptyloxy benzylidene) p‐n‐hexylaniline (70.6) and in N(p‐n‐octyloxy benezylidene) p‐n‐decylaniline (80.10) is carried out to study the nature of the phase transitions associated density jumps, to estimate the pressure dependence of transition temperatures and pretransitional effects. The compounds 70.6 exhibits a phase variant ACFG whereas 80.10 exhibits a new phase sequence variant ABF. The isotropic‐smectic A, semctic A‐smectic B and semctic C‐smectic F phase transitions are found to be first order. The calculated thermal expansion coefficient also supported the density results. The density jumps, associated enthalpies and estimated pressure dependence of transition temperatures at the isotropic‐smectic A phase transformation in other compounds are presented.
Rare‐earth scandium garnets as an object of crystallization
Authors: Zharikov E. V.
Published: January 2007

The paper discusses the features of RESG which influence the crystal growth. RESG are nonstoichiometric compounds with complex scandium isomorphism which results in substantial variations of the crystallized composition. The presence of chrormuim ions in RESG strongly increases the absorption capability of the medium and leads to the rise of interface instability during the growth. The principle differences between ScGa‐ and ScAl‐garnets concerning crystallization features are considered.
Crystallization of C16H32O2 from liquid hydrocarbon
Authors: Prasad P. B. V. , Prasad N. Durga
Published: January 2007

Studies on the crystallization of palmitic acid from liquid paraffin are discussed.
In‐situ doping of and trench‐refill with LPCVD‐poly‐silicon (I). (PH3/SiH4) ratio as a process‐controlling parameter
Authors: Kühne H. , Harnisch H. , Flohr I. , Bertoldi W.
Published: January 2007

The ratio of phosphine‐ to silane concentration in the reaction gas mixture is a processcontrolling parameter in LPCVD‐polysilicon deposition not only with respect to doping level of the layer and layer growth rate on planar wafer surface, but also with respect to the degree of growth rate depression occurring by change‐over from wafer surface to sidewall area within trenches in the region of the upper rim of a trench. Trench refill behaviour deteriorates in consequence of growth rate depression within trench the more the higher the doping level of poly‐silicon will be chosen. Yet below a lower limit of doping poly‐silicon growth rate equals that of undoped poly‐silicon, and, as for trench‐refill, there is no difference in layer growth within trench and beyond.
Optical properties of flash‐evaporated CuInTe2 thin films
Authors: Hörig W. , Neumann H. , Savelev V. , Lagzdonis J. , Schumann B. , Kühn G.
Published: January 2007

Optical absorption spectra of flash‐evaporated polycrystalline thin films of CuInTe2 are measured in the photon energy range from 0.5 to 3.0 eV. A gap energy in the range from 0.96 to 0.99 eV and a spin‐orbit splitting of the valence band of 0.61 ± 0.03 eV are derived from the spectra. It is found that the spectra are considerably influenced by grain boundary effects.
Solidification behaviour of BaB2O4 melts
Authors: Ovanesyan K. L. , Petrosyan A. G. , Shirinyan G. O.
Published: January 2007

Experimental evidence has been obtained that both α‐ and β‐phase BaB2O4 material can be grown directly from pure melts. Growth of α‐phase material onto a platinum rod is initiated by α‐phase structural centers present in the melts which are stable at temperatures around or just above the melting point. Overheated melts in which solid nuclei are destroyed have modified freezing characteristics and form β‐phase material. β‐phase material can be produced onto a platinum rod at temperatures well above the reported phase transition temperature.
The coprecipitation of magnesium hydroxoaluminate hydrates from aqueous solution with ammonium hydroxide: Precipitate compositions and coprecipitation mechanisms
Authors: Packter A. , Panesar K. S.
Published: January 2007

Magnesium hydroxoaluminate hydrates were coprecipitated from different mixed metal cation solutions at Mg/Al2 ratios from 1 to 4 by ammonium hydroxide. The coprecipitations were monitored by potentiometric titration and the final precipitate compositions were examined by chemical analysis, X‐ray diffraction, infra‐red spectrophotometry and thermal analysis. The process of coprecipitation was similar to that for coprecipitation with sodium hydroxide but large excess of ammonium hydroxide was required for complete reaction at pHs from about 8 to 10.

At Mg/Al2 = 1, the main phase was probably Mg(H2O)h [Al(OH)4]2;

at Mg/Al2 = 2, the main phase was probably Mg2(H2O)h [Al2(OH)10];

at Mg/Al2 = 4, the main phase was probably (MgOH4) (H2O)h [Al2(OH)10].
Nonstoichiometry in steps on AB crystals (I). General aspects, including bulk imperfections
Authors: Arnold H.
Published: January 2007

Starting with a quasichemical treatment, simple model calculations are given for the equilibrium composition in surface steps containing A and B kinks, the amount and ratio of which is varied by changing the adjacent gas composition. In connection with deviations from step stoichiometry, the total amount of kinks increases strongly.

A nearest neighbour approximation has been applied to the attachment of A or B atoms at kinks from the gas phase, and also from the bulk by formation of vacancies VA or VB. These processes can be formulated separately for the two elements, taking into account the effective formation of bulk atoms of the other kind (BB or BA).
Comparing investigation of the smectic C and A phases of the di‐n‐alkyl 4,4′‐azoxycinnamates (I). Calorimetric investigations
Authors: Wiegeleben A. , Diele S. , Demus D.
Published: January 2007

We present calorimetric investigations (DSC) of 9 members of the homologous series of the di‐n‐alkyl 4‐4′‐azoxycinnamates. The phase transitions smectic C/A and smectic A/isotropic are characterized by thermodynamic changes which are discussed comparingly. With increasing length of the n‐alkyl chains in the series the clearing temperatures are depressed, the SA regions are diminshed and the character of the phase transitions C/A changes from second order to the direction of first order.
Moisture resistance of polished and coated KCl windows
Authors: Nistor L. C. , Nistor S. V. , Teodorescu V. , Voda M. M.
Published: January 2007

The moisture resistance of ultratransparent KCl grown in a reactive atmosphere was studied on polished KCl samples coated with protective films of BaF2. The lifetime was improved about 4 times compared with uncoated samples. A further improvement was obtained by additional chemical polishing before coating. However, in such a case buckling of the film in a pattern of narrow parallel stripes was observed in an intermediate stage of the humidity test.
On normal kinetics in the case of some refractory and transition metals' crystallization
Authors: Baikov Yu. A. , Chistyakov Yu. D.
Published: January 2007

In given work the crystal growth kinetics connected with some refractory and transition metals is considered. For melts of Fe, Co, Ni, Cr, Zr, Ti, Ag, Cu, and Pb in the vicinity of melting temperatures the solid phase growth is described by means of a fluctuation theory applied for the macro‐systems. By virtue of the “unlimited” and limited spectrum solid state particle concentration fluctuations' theory some effective kinetic coefficients have been estimated in the work. The effective kinetic coefficients are specific in the case of normal crystal growth kinetics. In the case of the crystallization of Fe, Co, Ni, Cr, Zr, Ti, Ag, Cu, and Pb‐melts a comparison between two effective kinetic coefficients (based on the fluctuation theory and so‐called equilibrium growth points density) has been realized. In most cases a satisfactory agreement between the effective kinetic coefficients has been observed.
Undoped semi‐insulating GaAs crystals grown by a modified low pressure LEC method
Authors: Mo P. G. , Fan X. Q. , Zhou Y. D. , Wu J.
Published: January 2007

A modified low pressure in‐situ synthesis LEC method of growing undoped SI (semi‐insulating) GaAs crystals has been established. The key points for controlling melt composition and As evaporation during synthesis and growth have been described. Using this novel approach, crystals are able to be grown from the nominal melt composition in the range of 0.491–0.499 As fraction with high reproducibility. Some characteristics of the undoped SI crystals grown by the present work including electrical properties, dislocation density, carbon and EL2 concentrations and thermal annealing effects have been studied.
A new technique for carrying out real‐time measurements of crystal growth rate
Authors: Dong J. C. , Yu X. L. , Jiang H. Z.
Published: January 2007

The growth rates of crystal interfaces have been measured by using a new technique — the laser diffraction metering technique. It is simple, visualized, fast and has high precision. This paper describes the basic principle, operation method and the precision of the technique.
Lamellar eutectic growth at minimum entropy production
Authors: Wolczyński Waldemar
Published: January 2007

A mode of determination of entropy production per unit time for regular eutectic growth is presented. In order to integrate this thermodynamic quantity, both diffusion equation and coefficient of the interplay between curvature of an interface and concentration field are taken into account. The adaptation of the criterion of minimum entropy production allowed to show the equation (growth law) describing the lamellar structure formation under imposed temperature gradient and given growth rate for an alloy under investigation.
Crystal growth and twin formation of gypsum )
Authors: Bartels H. , Follner H.
Published: January 2007

Theoretical growth and equilibrium forms of gypsum have been determined by the Fourier transform method. Both are in good agreement with the experimental observations. There are some differences to previous publications which are based on energetic calculations by ionic interaction energies. It is possible to predict five planes of intergrowth. Two of them are wellknown in literature.
The annealing of alkaline‐earth metal polymetaphosphate powders (I). Crystallisation and sintering processes
Authors: Packter A. , Doherty W. O. S.
Published: January 2007

Amorphous barium, strontium, calcium and magnesium polymetaphosphate powders (MP2O6)n, n = 20 were prepared by dehydration of the corresponding polymetaphosphate hydrate precipitates. These powders were annealed by different continuous and isothermal heat treatments over the temperature range 450° to 700 °C, the glass transition temperatures Tg to above (Tg + 120) °C. The morphologies at different degrees of crystallisation were studied by scanning electron microscopy. For the main crystallisation process (ten to sixty‐seventy percent crystallisation), the powder particles retained their original pea‐pod form; then after seventy percent crystallisation, these crystallised particles sintered laterally to lozenge‐shaped twin‐hexagonal crystals of lengths 0.5 to 3 μm.

Differential thermal analysis confirmed that a markedly exothermic crystallisation process (overall enthalpy changes from about 30 to 45 kJ mol−1) was occurring within the powder particles. Crystallisation rates varied from < 0.005 min−1 at temperatures near Tg to > 0.5 min−1 at higher temperatures; the activation energies for this process varied from 360 to 560 kJ mol−1.

The completely annealed crystals were studied by scanning electron microscopy, X‐ray diffraction and further differential thermal analysis to 1000 °C. The X‐ray diffraction d value patterns, the fusion temperatures and the enthalpies of fusion were all in close agreement with the literature values for the corresponding beta alkaline‐earth metal polymetaphosphates prepared by melt crystallisation.
Growth, characterization and fabrication of n‐WSe2 PEC solar cells
Authors: Agarwal M. K. , Rao V. V.
Published: January 2007

Single crystals of n‐WSe2 have been grown by the chemical vapour transport (CVT) technique, using Br2, TeCl4, and SeCl4 as transporters. Crystal lattice parameters have been determined for all the crystals grown above with an X‐ray diffractometer. The composition of the above crystals were examined by energy dispersive analysis of X‐rays (EDAX). Optical and some electrical transport measurements are carried out to judge the semiconducting nature of the as‐grown crystals. Photoelectrochemical (PEC) solar cells were frabricated by using these crystals as photoelectrodes and platinum grid as counter electrode in an aqueous iodine/iodide solution. Some of the PEC cell parameters were determined. The results thus obtained have been discussed in detail.
Growth rate studies on n‐pentadecanoic acid crystals: Reversibility of A′ → B′ transition
Authors: Prasad P. B. V.
Published: January 2007

n‐Pentadecanoic acid has A′ → B′ and B′ ⇌ D′ transitions in the crystalline state. Information obtained from the growth rate studies on the crystals of this material is interpreted as an indication of reversibility of A′ → B′ transition.
Small angle neutron scattering in AlCuMg alloys
Authors: Schmidt Ulrike , Ostanevich Juri M.
Published: January 2007

The structure changes proceeding in AlCu 2.1 at.% Mg(x) alloys with magnesium concentration form 0 to 1.2 at.% at room temperature and 100 °C are followed by small‐angle neutron investigation. The results are fitted on different models. The most important result is that with increase of the Mg contents clearly a growth of the thickness opposite to the growth of the growth of the diameter to discern. The results give a good idea of the formation of GPZI(Mg) with the adequate portion of magnesium in the AlCuMg(x)‐alloys and their transition to GPZII(Mg) respectively θ″ (Mg).
DSC characterisation of various phase transitions in mesomorphic benzylidene anilines
Authors: Pisipati V. G. K. M. , Rao N. V. S. , Alapati P. R.
Published: January 2007

To analyse the order of the phase transitions in a number of mesomorphic benzylidene anilines, the DSC (Differential Scanning Calorimetry) method proposed by NAVARD and HAUDIN is used. This method involves the measurement of the ratio (N) of the DSC peak heights H2/H1 for a given transition, performed with two different heating rates (T2/T1). N is a function of the ratio r2/r1(= R) and the magnitude of N provides a simple way to characterize the order of a phase transition.
Ageing effect on dielectric properties of SnO2, Sb2O3, and their mixed thin films
Authors: Kumar J. Siva , Rao K. V. Satyanarayana , Rao U. V. Subba
Published: January 2007

Thin films of various thicknesses in the form of MIM structures have been prepared from the powders of high purity of SnO2, Sb2O3, and their mixed powders separately by the thermal evaporation technique in a vacuum of 10−5 Torr. The dielectric properties of these oxide thin films have been studied with ageing time and also with frequency at room temperature. The results obtained have shown that the capacitance and loss tangent of the structures initially fall off rapidly and thereafter they attain a constant value even after ageing the capacitors for about 20 days. The rapid fall of capacitance and loss tangent may be due to the rapid decrease in the density of defects due to ageing time. The results thus obtained on SnO2, Sb2O3, and their mixed thin film capacitors are presented and discussed.
Electro‐optical properties of InGaAs layers grown by hydride vapour phase epitaxy
Authors: Attolini G. , Bocchi C. , Fornari R. , Pelosi C. , Oswald J. , Pastrnak J.
Published: January 2007

A series of epitaxial layers of the InGaAs alloy were deposited on (001) oriented InP substrates by using hydride VPE technique. The layers were characterized by Double Crystal Diffractometry (DCD), Photoluminescence (PL), Hall effect and Capacitance‐Voltage (C‐V) measurements. The growth parameters and the quality of the grown layers are discussed on the basis of electrical and structural data analysis.
Peculiarities of columnar structure formation in electrodeposited CoW films
Authors: Shadrow V. G. , Boltushkin A. V. , Tochitskii T. A.
Published: January 2007

The microstructure of Co—W films with perpendicular magnetic anisotropy has been investigated. It is shown that the peculiarities of the columnar structure formation and the changes of magnetic and mechanical properties associated with them are accounted for by the electrodeposition conditions and adsorption of the products of electrode reactions at the cathode.
Crystal structure and magnetic properties of some Mn2Sb‐based alloys
Authors: Ryzhkovskii V. M. , Zhigadlo N. D. , Pashkovskii I. L.
Published: January 2007

The results of the investigation of structural and magnetic properties of the Mn2(Ni)Sb, Mn2(Cr,Cu)Sb Mn2(Ti,Zn)Sb alloys are reported. The solubility limits of the elements substituting Mn in the Mn2Sb matrix, keeping the crystal structure of the Cu2Sb(C38)‐type, are established and the lattice parameters temperatures of magnetic phase transitions, specific magnetization of the materials are determined. The influence of thermal treatment and thermal cycling on the magnetic properties of the alloys, which is interpreted by the quantitative redistribution, depending on temperature, of the amount of the main δ‐phase (C38) in the samples, with the phase composition changing, and that of an additional nickel‐arsenide ϵ‐phase has been found.
Effective kinetic coefficients for some binary metallic alloys within the small and finite supercooling region
Authors: Baikov Yu. A. , Chistyakov Yu. D.
Published: January 2007

The normal crystallization kineties concerning the base of In, Rb, Ga some binary metallic melts either within the small supercoolings (Δ T ≦ 1 K) or finite ones (ΔT ≦ 20 ÷ 60 K) has been considered. When crystallizing the binary alloys: In + 2.3 at.% Pb; Rb + 10 at.% K; Ga + 2 at.% Sn; Ga + (2; 4; 8) at.% In; Ga + (0.5; 3.5) at.% Zn; Ga + (5; 8; 10) at.% Zn very dilute binary solid solutions are supposed to be formed. The solid solutions have the B‐component distribution coefficients which are either much less or less compared with unit, i.e. kB ≦ 1, kB < 1 in all the layers of diphase transition region separating the melt from the crystalline phase. By virtue of fluctuation theory of normal crystal growth within the small and finite supercoolings' region for the above‐mentioned binary metallic melt some effective kinetic coefficients have been calculated. A good agreement between theoretical effective kinetic coefficients and available experimental ones in the case of given binary systems has been established.
The influence of the Mg content and the quenching conditions on the decomposition kinetics of AlZnMg alloys
Authors: Wolter R. , Fabian H.‐G. , Czurratis P. , Kroggel R.
Published: January 2007

By means of resistivity measurements, TEM and microhardness measurements the decomposition kinetics of A1‐3 at.% Zn‐1.5 at.% Mg and A1‐4.5 at.% Zn‐x at.% Mg (x = 0.2; 0.5; 1.0; 1.5; 2.25; 3.0) were investigated. For Ta < Ta, crit < Th (Th: temperature of the rapid homogenous nucleation) in A1‐3 at.% Zn‐1.5 at.% Mg and A1‐4.5 at.% Zn‐x at.% Mg (x = 1.0; 1.5; 2.25; 3.0) an inversion of the decomposition kinetics for Tq > Tinv: (Tinv: inversion temperature) was established. This result can be explained with reference to the binding of excess vacancies in dislocation loops.

Proceeding from the discrepancy between the experimentally estimated concentrations of vacancies bound in dislocation loops and the concentrations of free vacancies at Tq, calculated by means of the Lomer equation, a model is proposed, which explains the high vacancy concentration of the loops. In terms of this model the values of the migration energy, obtained for A1‐3 at.% Zn — 1.5 at.% Mg in the Ta‐range 23 °C ≦ Ta ≦ 100 °C, and the shift of the inversion temperatures Tinv towards higher values with increasing Ta are interpreted. The same applies to the influence of the Mg content on the decomposition kinetics in A1‐4.5 at.% Zn‐x at.% Mg alloys.
Minimum undercooling condition as a particular case of the criterion of minimum entropy production
Authors: Wołczyński Waldemar
Published: January 2007

The attempt to compare the diffusional‐thermal model based on the criterion of minimum entropy production to diffusional one based on the condition of minimum undercooling has been presented for regular eutectic growth. Finally, the general relationship describing lamellar structure formation is to be reduced to another one proposed by Jackson and Hunt's theory. This reduction has been in great part obtained. However, it remain some equivalent terms, which are not identical. It is probably produced by some imperfections of Jackson and Hunt's model, as well as any other adversities, e.g., some different assumptions in both compared models. The reduction of the criterion of minimum entropy production to the condition of minimum undercooling has also been suggested.
Etching of silicon trenches in CF4 plasma using photoresist/aluminium masks
Authors: Glück B. , Höppner W.
Published: January 2007

The reactive ion etch process (RIE) of silicon in a CF4/O2 gas mixture is described. The dependence of the etch rate and the surface quality on used mask material (photoresist, aluminium) is studied.

A silicon etch rate of about 1.5 times higher than with resist mask is reached using aluminium as mask material. The free etched surfaces are very rough due to micromasking effects during the etch process. Using a phtoresist mask the surfaces remain clean. The silicon etch depth depends on the thickness of the mask.
Crystal structure analysis and refinement of Kalabsha kaolinite (Al2Si2O5(OH)4)
Authors: El‐Sayed Karimat , Heiba Z. K. , Abdel‐Rahman A. M.
Published: January 2007

The crystal structure of the kaolinite mineral from Kalabsha, Aswan, Egypt, has been investigated with a two‐step procedure of the X‐ray powder pattern‐fitting. The unit cell is found to be triclinic, P1, a = 5.1577(15), b = 8.9417(23), c = 7.3967(40) Å, α = 91.672(5)°, β = 104.860(2) and γ = 89.898(2)°. The refinements of the non‐hydrogen atomic positions showed a reliability factors RWB = 0.037 and RB = 0.0417. The average rotation angle in the tetrahedral layer in 10°.
X‐ray studies of binary mixtures of smectics A1 with a nematic gap and reentrant nematic phase
Authors: Ważyńska B. , Przedmoj̇ski J.
Published: January 2007

Binary mixture of 80BCAB—10TPCHB system are investigated. It is shown that the dimerization of 80BCAB compound in the matrix of 10TPCHB takes place as it was in 7CBB—10XPCHB systems. The generalized conclusion is drawn that such a behaviour is common for homologous series the members of which with shorter aliphatic chains yield the smectic A1 phase and those with longer chains the Ad one.
Crystal and molecular structure of 2‐diazo‐5‐phenyl‐cyclohexan‐1,3‐dione
Authors: Ramm M. , Schulz B. , Thurner J.‐U. , Ulbricht M.
Published: January 2007

Mr= 214.24, monoclinic space group P 21,a= 10.964(2),b= 5.870(2),c= 8.574(2) Å, β = 98.09(2)°,V= 546(1) Å3,Z= 2,Dx= 1.302 Mg m−3,F(000) = 224, λ (MoKα) = 0.71069 Å, μ = 0.8 mm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factorR= 0.034.

Mr= 214.24, monokline Raumgruppe P 21,a= 10.964(2),b= 5.870(2),c= 8.574(2) Å, β = 98.09(2)°,V= 546(1) Å3,Z= 2,Dx= 1.302 Mg m−3,F(000) = 224, λ(MoKα) = 0.71069 Å, μ = 0.8 mm−1.
The influence of the direct quench and indirect quench to Ta > Th on the decomposition behaviour of an Al‐2 at.% Zn‐1 at.% Mg alloy
Authors: Wolter R. , Fabian H.‐G. , Czurratis P. , Kroggel R.
Published: January 2007

The decomposition behaviour of an Al‐2.0 at.% Zn‐1.0 at.% Mg alloy after direct quench (DQ) and indirect quench (IQ:T = 23 °C, t) to the ageing temperature T = 160 °C (above the temperature of the rapid homogeneous nucleation, Th) was investigated by means of TEM and isothermal resistivity measurements. The precipitation density of the η‐particles yields a maximum value at pre‐ageing times about 10 min at T = 23 °C. To clear up the reason for that phenomenon a loop‐formation and clustering model was introduced.
Life time measurements of charge carriers in layer MoSexTe2−x (0 ≦ x ≦ 2) PEC solar cells
Authors: Agarwal M. K. , Patel P. D. , Joshi R. M. , Rao V. V.
Published: January 2007

Layer type MoSexTe2−x (0 ≦ x ≦ 2) are grown by chemical vapour transport technique. The photoelectrochemical (PEC) solar cells are fabricated using the grown single crystals as photoelectrodes and platinum grid as counter electrode. The life time measurement of charge carries were carried out using pulse light from a stroboscopic source. The variation of life time with temperature and composition have been studied. The results thus obtained have been concluded.
Coefficient of volume expansion and thermoacoustic parameters in certain alkoxy benzylidene butylanilines — IB
Authors: Venkatacharyulu P. , Prasad K. S. R. , Kasturi A. , Prasad N. V. L. N. , Rao J. V.
Published: January 2007

Using the coefficient of volume expansion certain thermoacoustic parameters like isobaric (K), isothermal (K″), isochoric (K″) acoustic parameters, free volume (Va/V) and two new dimensionless acoustic parameters A* and B* are estimated in certain alkoxy benzylidene butylanilines, in their isotropic‐ and mesophases as well as at and in the immediate vicinity of the phase transition temperatures following the method which was suggested by Sharma, for non‐mesomorphic systems.
Paramagnetic defects in the mineral hauyne
Authors: Vassilikou‐Dova A. B. , Lehmann Gerhard
Published: January 2007

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

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

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

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

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

The experimental and theoretical investigations of the nucleation processes of the calcium tartrate crystals in gel are presented in this paper. It has been shown experimentally that the changing of the acidity of the crystallogenetic media strongly influences the depth of the first crystals arising in gel, as well as on the crystals number and the mean mass of one crystal. The acidity changing was done by proton introduction into the gel formed by means of the additional solution (impregnation) or by means of the creation of proper acidity of maternal calcium chloride solution.

The theoretical description of this phenomena needs the assumption of the equivalence condition. The equivalence means that the concentration of crystal‐forming reagents can't differ very much.
Growth and characterization of mercurous chloride single crystals
Authors: Baskar K. , Gobinathan R.
Published: January 2007

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

Fresh and old as‐grown {001} surfaces of α‐HgI2 platelets were studied by optical microscopy. The presence of growth hillocks and the high value of the surface entropy factor are proofs of the spiral growth of platelets. In air surfaces became gradually dull. Consequently, the final micromorphology of HgI2 is the result of both growth (primary) and post‐growth (secondary) processes. For the revelation of defects a new, reliable etchant was used.