bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth of sizable single crystals of Y–Co Compounds
Authors: Warchol S. , Modrzejewski A.
Published: January 2007

The Bridgman method was used for the growth of sizable single crystals of Y2Co17, Y2(Co, Fe)17, Y2(Co, Al)17, Y2(Co, Fe, Cu)17, Y2(Co, Fe)23, and YCo5. Yttrium metal was melted in Co or Co–Fe ‘container’ placed in Al2O3crucible coated with BN layer. The crystals were grown at a rate of a few millimetres per hour by lowering the crucible in the heating zone of induction furnace.
Structures of Azomethine Imines of the Pyrazolidone‐(3)‐type, (III) The Structure of 1‐[Anthryl‐(9)‐methylene]‐pyrazolidone‐(3)‐betaine
Authors: Kulpe S. , Seidel I. , Geissler G.
Published: January 2007

C18H14N2O, Pbca,a= 19.541(4) Å,b= 14.800(2) Å,c= 9.572(3) Å,Z= 8,U= 2768.3 Å3,Dx= 1.32 g cm−3, μ(MoKα) = 0.93 cm−−1, crystal size 0.5 × 0.2 × 0.1 mm, colourless. FinalR= 0.077 for 1177 independent reflections excluded those with |F0| < 8 σ(F0).

The intensities were measured with an automatic diffractometer. The azomethine imine unit of the molecule has a geometry in approximate agreement with a polymethinic electron structure. The conjugation of the azomethine imine unit with the anthryl unit is only small. The anthryl ring and the five membered pyrazolidone ring include a dihedral angle of 65.4°. The main intermolecular forces are C–H … N hydrogen bridges.
Investigations of Dissolving Mechanically Processed Quartz Grains
Authors: Steinike U. , Hennig H.‐P. , Richter‐Mendau J. , Kretzschmar U.
Published: January 2007

The dissolution of polycrystalline quartz strained by compression and shear or by impact crushing in 1‐N NaOH lead to different results. The defects of the impact crushed quartz grains, measured as crystallinity by X‐ray methods, are not preferentially concentrated in regions near the surface. It is assumed that in this case the corners and edges of the quartz grains are preferred centers of defects.
Defects in implanted and Czochralski silicon
Authors: Salisbury I. G.
Published: January 2007

Rod‐like defects, a6〈114〉 and a/3〈111〉 faults, and a/2〈110〉 loops may all be generated by self‐interstitial aggregation during the annealing of implanted or Czochralski silicon, and several models, intended to account for one or more of these, are compared. It is concluded that the rod‐like defects are {113} faults, and that the three faulted defects form independently (i.e. they are not related in an „evolutionary”︁ sequence). The dipolelike a/2〈110〉 loops probably result from the unfaulting of {113} faults, while other perfect loops are generated by the shear of a/6〈114〉 defects. At a given temperature, the latter appear considerably more likely to unfault than the a3〈111〉 faults. The structure of the {113} fault remains uncertain.
On the morphology of the unidirectionally solidified AgSi eutectic alloy
Authors: Chrost Krystal , Frühauf Joachim , Schmidt Günther
Published: January 2007

It is known that the structure of anormal eutectics occurring in the systems metal‐Si, metal‐Ge strongly depends on the conditions of growth ‐ that is, on the solidification rate R and the temperature gradient G. Structures occurring in the unidirectionally solidified AgSi eutectic alloy with morphology corresponding to region B according to classification adopted by HELLAWELL for the system AlSi were investigated. For the description of the morphology, three parametres were adopted: λ ‐ distance between the centres of Si crystals, d ‐ length of arms of cross‐like crystals, b ‐ thickness of Si plates.

It has been found that at similar morphologies of Si crystals, expressed by constant values of the relation λd, the known relation λ2R = const. is fulfilled, too.
The defect structure of ammonium sulphate single crystals
Authors: Van Enckevort W. J. P. , Boeshaar H. J. , Linden W. H. Van Der , Van Der Hoek B.
Published: January 2007

The defect structure of larger ammonium sulphate crystals, grown from aqueous solutions, has been studied by means of X‐ray diffraction topography after Lang's method. Several types of dislocations were identified. Moreover it was found that no relationship exists between growth rate and dislocation density, which implies that crystal growth proceeds via two‐dimensional nucleation. No difference was found in the defect structure of crystals grown from pure water solutions and from aqueous solutions with 10 – 20% glycerine as additive: In both cases neither growth bands nor sector boundaries were found. On the other hand, crystals grown in aqueous solutions contaminated with Mn2+ and Fe3+ revealed growth bands and for Fe3+ a mosaic‐like structure.
Impact damage in MgO single crystals
Authors: Remón A. , Piqueras J. , Llopis J. , Ballesteros C.
Published: January 2007

Optical absorption has been used to study the impact damage in MgO and MgO:Li single crystals. The results are similar to that obtained in compressed crystals, except in MgO:Li with stable Li° defects, in which the impacts do not produce an increase of the 5.7 eV absorption band.
Structures of azomethine imines of the pyrazolid‐3‐one‐type (V). The structure of 1‐[pyrenyl‐(1)‐methylene]‐5,5‐dimethyl‐pyrazolid‐3‐one‐betaine.
Authors: Kulpe S. , Seidel I. , Geissler G.
Published: January 2007

C22H18N2O, P21, a = 7.473(2), b = 13.563(3), c = 18.264(3) Å, β = 115.49(4)°, Z = 4, U = 1670.9(6) Å3, Dx = 1.295 Mg m−3, μ(MoKα) = 0.855 cm−1, crystal size: 0.3 × 0.2 × 0.2 mm, colour: yellow. Final R = 0.086 for 1973 independent reflections excluding those with |F0 < 3σ(F0). The intensities were measured with an automatic diffractometer. There are two symmetrically independent molecules in the unit cell. The azomethine imine parts of the molecules are similar to those of four other relevant structures determined by X‐ray analysis. A polymethinic part of a molecule is linked with an aromatic part via the bond C(4)–C(5). The mean pyrenyl plains and the mean plains of the five membered rings include dihedral angles of 29.6° for molecule A and 23.7° for molecule B.
Precision lattice parameter determination of coloured quartz monocrystals
Authors: Grosswig S. , Härtwig J. , Alter U. , Christoph A.
Published: January 2007

Several possibilities for the determination of relative lattice parameter changes and for the absolute measurement of lattice parameters are discussed. Special attention has been given to a measuring device for the high‐precision lattice parameter determination according to the BOND method. This device allows to determine the lattice parameters with a relative accuracy of 2 × 10−7. As an example the methods discussed are applied to the investigation of a smoky coloured quartz crystal plate and the results obtained by them were compared.
On batch homogeneity in horizontal CVD reactors (I). Model of heating the process gas
Authors: Richter F.
Published: January 2007

A model of heating of the process gas during its flow along the heater is given as a supposition for a modelling of the batch homogeneity with layer deposition and gas phase etching processes in horizontal CVD‐reactors. An analytical expression is derived for the resulting longitudinal temperature profile T(x) in dependence of gas properties, suszeptor temperature, geometric parameters of the reactor, and gas flow rate.
Dielectric relaxation and Freedericksz effect
Authors: Kresse H.
Published: January 2007

We have found that the dielectric anisotropy Δ′ of 4‐n‐butyloxy‐4′‐n‐pentyl‐azobenzene is positive at all frequencies. There is in the MHz region a dielectric dispersion for ϵ′” only which gives a decrease of Δ′. By means of Freedericksz effect was investigated a new variant for the dependence of electrical orientation on the frequency.
Double heterostructure lasers prepared by LPE on medium‐quality GaAs substrates under controlled as vapour conditions
Authors: Novotný J. , Šrobár F. , Zelinka J.
Published: January 2007

The fact that defect formation in (Ga, Al)As LPE layers can be suppressed by the presence of arsenic vapour is employed to improve properties of double heterostructure (DH) lasers. The controlled vapour pressure (CVP) method is implemented using a modified LPE horizontal carbon boat. Growth kinetics study under near‐equilibrium conditions shows that the presence of arsenic vapour diminishes the growth rate of aluminium‐containing layers; no such influence has been observed with the GaAs layers. The CVP method, compared with the customary LPE, has a beneficial effect on the DH surface and cross sections perfection, as well as on the lasing characteristics (differential quantum efficiency, threshold current). Observed values of the parameter T0, characterizing temperature dependence of the laser threshold current, fall into the vicinty of 200 K. The results have been obtained on medium‐quality GaAs substrates.
Simple theoretical estimate of surface energy, bulk modulus, and atomization energy of AIBIIIC compounds
Authors: Neumann H.
Published: January 2007

The specific surface energy of the (112) face of the chalcopyrite structure AIBIIIC2VI compounds is calculated accounting for contributions from long‐ranged, metallic forces and short‐ranged, directional covalent forces. From the surface energies the bulk modulus and the atomization energy of all AIBIIIC2VI compounds are evaluated. A comparison with experimental data shows that the trends in these quantities are correctly described whilst their absolute values are overestimated by not more than about 10%.
Characterization of treated pbte surfaces by means of RHEED and RBS
Authors: Salewski W. , Schenk M.
Published: January 2007

Differently treated PbTe surfaces have been investigated by means of reflection high energy electron diffraction (RHEED) and Rutherford backscattering (RBS). It has been shown that chemical lap polishing followed by heat treatment is the best method to fulfil the requirements of the following epitaxy process concerning the absence of contaminations, the high structural surface perfection, and the flatness of the substrates.

The influence of heat treatment on surface perfection, and chemical composition in the surface region has been investigated to determine the optimal conditions for the tempering step before epitaxy.
Isothermal contact of III–V saturated solutions with different III‐V substrates: Two mode of behavior
Authors: Bolkhovityanov Yu. B.
Published: January 2007

A correlation is established between the relaxation mode of non‐equilibrium solid‐liquid interfaces and the sign and magnitude of the lattice mismatch between a substrate and the solid which is in equilibrium with the liquid phase contacting the substrate. For a positive mismatch of a resulting film and the substrate the relaxation proceeds via substrate dissolution or spatially separated dissolution and growth; for a negative mismatch the melt droplets penetrate into the substrate. To illustrate this correlation we use examples from the literature as well as our own experimental results on isothermal contact of binary and ternary III‐V melts (saturated with respect to native solids) with different III‐V substrates.
Fluctuation mechanism of normal crystal growth during solidification of binary metallic melts
Authors: Chistyakov Yu. D. , Baikov Yu. A. , Schneider H. G. , Ruth V.
Published: January 2007

A recently published theory on the solidification of a one‐component melt has been extended to the more complex case of binary systems. The theory is based on the model of a two‐phase transitional zone existing between the crystalline phase and the melt. The concentration of solid state atoms within each mono‐atomic layer of the transitional zone are assumed to fluctuate due to thermal fluctuations. A crystal growth law has been derived expressing the crystallization velocity in terms of probability functions describing these concentrations fluctuations. When certain restricting conditions concerning the atomic interaction energies within the transitional zone and the distribution of the atoms among the solid and liquid phases at supercooling are fulfilled the crystal growth law attains a simple form predicting for small supercoolings a growth rate proportional to supercooling (linear growth law), roughly proportional to physical parameter θAA, and with a weak dependence on another parameter Δ.
Growth and morphology of p‐terphenyl single crystals
Authors: Borecka B. , Lipiński A.
Published: January 2007

The results of a preliminary investigation of the growth and morphology of p‐terphenyl crystals grown by sublimation and by solvent evaporation methods are reported. It was observed that lozenge–shaped (001) crystal plates are obtained from xylene and benzene solution while dendritic crystals by sublimation. Crystallographic orientation of the plates and microscopic observations of as‐grown crystal surfaces are also described.
The morphotropy phase transition in PZT‐Pb(WCd)O3‐ ceramics
Authors: Kwapuliński J. , Kupriyanov M.
Published: January 2007

The changes of the crystal lattice parameters of the solid solution formed on the basis of PbTiO3 and PbZrO3 with the constant addition of 10 mol percent PbW0.5Cd0.5O3 has been investigated. In samples containing 37.5 to 45.5 mol percent of PbTiO3 the coexistence of two phases was observed. In this concentration region the change of lattice constant and homogeneous parameter of deformation appeared.
Formation and properties of carbon black at high‐temperature pyrolysis of hydrocarbons and the role of ions
Authors: Schierhorn E. , Spangenberg H.‐J. , Lachmann J. , Steinike U.
Published: January 2007

The thermal decomposition of hydrocarbons during high‐temperature pyrolysis is described, and the resulting formation of carbon black is explained by a radical mechanism. Structural properties of acetylene and plasma blacks determined by electron microscopy and X‐ray diffraction are given. Measurements with an electrical probe revealed a direct relation between the ion density in the plasma and the number of primary carbon black particles.
An estimation of the angular correlation curves being characteristic of positron annihilation in dislocations, vacancies, and vacancy clusters in Ni
Authors: Dlubek G. , Meyendorf N. , Brümmer O.
Published: January 2007

Angular correlation curves are measured in Ni‐0.1 at.% Sb; 90% cold‐rolled during isochronal annealing. The behaviour of the parameters S, W, and R is interpreted by the formation of three‐dimensional vacancy clusters nucleated at Sb atoms. Using results of positron lifetime measurement previously performed we estimate the angular correlation curves being characteristic of positron annihilation in bulk, dislocations, vacancies and vacancy cluster of different size (n = 5, 10, 20, and 50 vacancies per cluster).
Reactivity of CCl4 plasma against SiO2 surfaces
Authors: Tiller H.‐J. , Göbel R. , Breitbarth F.‐W.
Published: January 2007

SiO2 is etched considerably by a CCl4 plasma at surface power densities of about 0.3 W cm−2. This etching process is investigated by the SiCl4 formation with aid of mass spectroscopy where final products of the etching process and the extracted ions were studied in dependence on time in a closed plasma volume. The primary step of the etching process is the activation of SiO2 by the plasma involving breaking of siloxan bridges.

The overall mechanism of the SiO2 etching by the CCl4 plasma is proposed in form of magnified image The rate limiting constants are k0 and k3. The SiCl4 formation is decreased or inhibited by an admixture of Cl2, H2, O2 or CO to the CCl4 plasma.

CCl4‐Plasmen führen zu einem Ätzangriff an SiO2‐Oberflächen. Dieser Ätzprozeß ist bei Leistungsdichten an der zu ätzenden Oberfläche von > 0,3 W cm−2 deutlich über eine SiCl4‐Bildung nachweisbar. Der Primärschritt ist eine Aktivierung der SiO2‐Oberfläche durch das Plasma, die zu Bindungsbrüchen der Siloxanbrücken führt.
Mesoscopic and microscopic aspects of the PSB formation mechanism in fatigued FCC monocrystals
Authors: Blochwitz C. , Burmeister H.‐J. , Kremling U.
Published: January 2007

Persistent zones of plastic strain localization (PSBs) can be observed in fatigued fee monocrystals above the “nucleation cycle number” Nn and the “nucleation stress” amplitude τn, respectively. They follow after temporary strain localizations existing at N < Nn and being discernible by oscillations of the relative shape of the hysteresis loops (VH) or by strain bursts. Using a simple rheological model the frequency of internal stresses of mesoscopic wave length (“mesoscopic stresses”) was determined for Ni monocrystals fatigued at four different plastic strain amplitudes up to Nn. A “mesoscopic threshold stress” τ* has been found to be exceeded within the whole volume of the dislocation‐dense regions (DRs) at N ≧ Nn. By comparison of τ* with the stress for the operation of Frank‐Read sources of the segment lengths l0 at the border of the DRs, it might be assumed that above Nn and τn respectively a mechanism of dislocation sources acts, compensating the high annihilation rate of movable dislocations in the zones of strain localization. In so doing the formation of persistent zones of strain localization becomes possible, in which the “ladder‐like” dislocation structure of the final PSBs develops successively.
Surface morphology and growth mechanisms of argyrodite‐type Cu6PS5 hal crystals
Authors: Fiechter S. , Eckstein J. , Van Enckevort W. J. P. , Binsma J. J. M.
Published: January 2007

Single crystals of Cu6PS5Hal (Hal = Cl, Br, I) have been grown by dissociative sublimation and by chemical vapour transport with P, S, Hal, CuHal and combinations thereof as transporting agents in the temperature range 800 to 1000 K. Microscopic observation of the tetrahedral faces revealed several growth features. Macrosteps, closed loop steps and surface protuberances are always accompanied with the presence of liquid CuHal/Cu2S droplets on the growing crystal surface. The phenomena are characteristic for a two‐dimensional Vapour‐Liquid‐Solid growth mechanism. In the absence of CuHal/Cu2S liquid phase, direct growth from the gas phase (VS growth) takes place leading to hillocks and growth spirals with low step heights (∼ 5–10 Å).
Periodic precipitation of barium molybdate in silica gel
Authors: Kurien K. V. , Vaidyan V. K. , Ittyachen M. A.
Published: January 2007

The mechanism of formation of the rhythmic pattern of precipitate of barium molybdate in one‐dimensional Liesegang phenomena is investigated quantitatively. They rhythmicity is found to be influenced by the molarity of inner and outer electrolytes and pH of the gel medium. The ‘time‐law’, ‘spacing‐law’ and ‘Δx‐law’ are verified.
(110) Twins of n‐C28H58 crystals: Habit changes and lattice net studies
Authors: Prasad P. B. V. , Raju I. V. K. Bhagavan
Published: January 2007

The (110) twins of normal octacosane crystals with hexagonal shape are observed. Various factors that may lead to a shape change are considered. Effect of growth rate anisotropy on the reentrent faces is studied with the help of growth patterns which are derived from a lattice net.
Phase transformation in a linear polycrystal with a rate law of n‐th order
Authors: Schulze G. E. W.
Published: January 2007

A phase transformation in a one component polycrystal starts to grow instantaneously and with a constant rate from the grain boundaries. After the time t there exist regions of the old and of the new phase. The derivation of the statistical quantities characterizing this state at t is unknown yet. Therefore we reduce this complicate three‐dimensional problem to a one‐dimensional model analogously to the linear chain in lattice dynamics or to the one‐dimensional energy band model. A closed analytical treatment of this model is practicable. It is derived in detail for those one‐dimensional systems, which transform according to a rate law of n‐th order (n ≧ 0).
The crystal structure of dodecyltrimethylammoniumbromide
Authors: Szulzewsky K. , Schulz B. , Vollhardt D.
Published: January 2007

C15H34BrN, monoclinic, P 21/m,a= 21.603(9),b= 7.261(3),c= 5.636(2) Å, β = 86.85(2)°,Z= 2,V= 882.72 Å3,Dx= 1.160 g/cm3, μ(MoKα) = 2.45 cm−1, λ(MoKα) = 0.71069 Å. The structure of this cationic surfactant was solved with Patterson methods and refined toR= 0.091 for 2057 measured reflections. The dodecyl chains are slightly screwed around their chain axes. The hydrocarbon chains are statistically disordered. The polar regions satisfy the mirror plane which is by remaining parts only statistically fulfilled. In the process of structure refinement statistical disorder has been included by separation of some atom positions. The sublattice of the hydrocarbon chains is nearly O⟂ withas= 5.14,bs= 7.26,cs= 2.52 Å.
Influence of film structure on the electron energy loss spectra of GaAs thin films
Authors: Boudriot H. , Kubier B. , Deus K. , Gründler R. , Kusior E.
Published: January 2007

Energy loss measurements of fast electrons on GaAs yielded values for the plasma oscillation, interband transitions and the dielectric function in the region 5 — 30 ev. The results are discussed in comparison with literature statements. It is dealt especially with the influence of the degree of crystallinity of examined GaAs‐films on the energy loss spectrum and the quantities derived from it.
Study of the complex vibrational spectra of natural mesolite
Authors: Pechar F.
Published: January 2007

The vibrational spectra of the natural zeolite, mesolite (locality Akureyri‐Island) were measured in the infrared (200—400 cm−1) and the far infrared — FIR (40—400 cm−1) regions: the infrared reflectance (200—1400 cm−1) and Raman scattering (50—3600 cm−1) spectra of the polycrystalline material were also measured.

The Schimanouchi GCCC, BGLZ, and LSMA programs were used to calculate the force constants and vibrational frequencies of the SiO, AlO, OH, cation‐oxygen, OSiO, OAlO, HOH bonds and libration of H2O and Si(Al)OSi on the basis of the symmetry coordinates. The KKK‐1 program (Petzelt, Kroupa) was used to calculate the dispersion curves of the complex refractive index for both parts of the complex dielectric permittivity in the whole measured wavenumber region. The bands in the spectra were assigned to the vibrations of the individual bonds and structural groups of the mesolite on the basis of theoretical calculations.
New liquid crystalline tetrazine derivatives for guest‐host displays
Authors: Isenberg A. , Krücke B. , Pelzl G. , Zaschke H. , Demus D.
Published: January 2007

A number of new liquid crystalline tetrazine derivatives was synthesized. The electro‐optical studies showed that the 3‐n‐alkyl‐6‐[4‐(4‐n‐alkyl‐cyclohexanoyloxy)phenyl]‐1,2,4,5‐tetrazines are excellent dyes for guest‐host displays with positive colour contrast.
The molecular and crystal structure of 2‐oxo‐1‐pyrrolidine‐acetamide
Authors: Pritzkow W.
Published: January 2007

C6H10N2O2, P1, a = 6,607(2) Å, b = 8,538(2) Å, c = 6,392(2) Å, α = 102,43(2)°, β = 91,11(2)°, y = 79,82(2)°, V = 349,1 Å3, Z = 2, Dm = 1,36 g × cm−3, Dx = 1,35 g × × cm−3, MoKα radiation, λ = 1.71069 Å, μ(MoKα) = 1.11 cm−1. The structure was solved by direct methods. The parameters were refined by full matrix least squares technique to a final R = 0.088 for 834 reflections with ∥F0∥ > 4σ(F0). The dihedral angle between the least‐squares plane through the pyrrolidine ring and that through the acetamide group is 90.4°. The NH … O hydrogen bonds connect molecules to form bands parallel to the z axis.
A topological approach to studies of ordered structures of absorbed gases in host lattices (I). The structure of γ‐PdD0.5
Authors: Fritsche H.‐G. , Bonchev D. , Mekenyan O.
Published: January 2007

A graph‐theoretical method is proposed which describes the deformation caused in the host lattice by absorbed gas atoms, as well as their ordering. The method predicts correctly the ordered γ‐phase of PdD0,5.
Gas bubble associated mass transport in Bridgman‐Stockbarger melt growth system
Authors: Petrosyan A. G.
Published: January 2007

Experimental evidence has been obtained showing that gas bubbles may be responsible for melt stirring in Bridgman‐Stockbarger growth system which results in Pfann type impurity distribution profiles along the crystal length. The hypothesis of the gas bubble associated mass transfer mechanism is supported by the production of Y3Al5O12–Nd3+ single crystals under conditions which eliminate or limit gas bubble nucleation in the melts with Nd3+ distribution profiles similar to those generally observed in melt growth systems where the mass transport in the melts is limited to diffusion.
Needle‐shaped and platelet growth of borax crystals
Authors: Takoo R. K. , Joshi M. S. , Patel B. R.
Published: January 2007

Needle‐shaphed and platelet growth of borax crystals from solutions is reported. Results of microtopographical studies on both the varieties are discussed. It is suggested that a slow rate of evaporation favours needle growth and a faster rate is conducive to the growth of platelets.
The precipitation of calcium hydroxoaluminate hydrate powders from sodium hydroxoaluminate solutions: Precipitate phases and precipitation mechanisms
Authors: Packter A. , Derry A.
Published: January 2007

Calcium hydroxoaluminate hydrates were precipitated from different sodium hydroxoaluminate and hydroxoaluminate‐excess hydroxide solutions at ambient temperature (at CAl = 0.1 to 0.3 M and at XS OH/Al = 0 to above 8). The precipitations were monitored by potentiometric (pH) measurements. Precipitate morphologies were examined by optical microscopy and precipitate compositions were determine by chemical analysis, infra‐red spectrophotometry and thermal analysis.

Generally at OH/Al ratios of 4 to 4.5 (XS OH/Al = 1 to 1.5), the compound 2 CaO · · Al2O3 · 8 H2O (C2AH8) was precipitated with some aluminium hydroxide; then at OH/Al ratios of 5 to above 11 (XS OH/Al = 2 to above 8), the compound 2 CaO · Al2O3 · 8 H2O was precipitated with increasing amounts of the compound 4 CaO · Al2O3 · 13 H2O (C4AH13).
A thermoluminescence study of Z2‐centres in terbium‐doped NaCl crystals
Authors: Reddy K. Narasimha , Ahmed Md. Iqbal , Pandaraiah N. , Rao U. V. Subba , Babu V. Hari
Published: January 2007

Thermoluminescence (TL), optical absorption are used to correlate thermal annealing of Z2‐centres with TL peak occurring around 110 °C in Terbium doped NaCl crystals. The TL glow peak occurring around 190 °C it attributed to the thermal annealing of F‐centres. The thermal activation parameters are calculated for both Z2‐ and F‐centre peaks.
Deformation and microhardness studies on KClO4 single crystals
Authors: Bhatt V. P. , Patel R. M. , Desai C. F.
Published: January 2007

The deformation characteristics of KClO4 single crystals have been studied by the methods of static and dynamic indentation on (001) plane. The cracks produced by the dynamic indentation have been interpreted in terms of slip‐twin interactions. Also, the load dependence of Vickers microhardness and its anisotropy in this crystal are reported. The observed hardness anisotropy has been used to confirm the indices of the slip system 〈101〉 〈111〉 operative in this crystal at ordinary temperatures.
The relaxation behaviour of strenght and fracture toughness of amorphous metal‐metalloid alloys
Authors: Wetzig K. , Pompe W. , Fiedler H. , Aljochin V. P.
Published: January 2007

The effect of an annealing treatment on crack and fracture kinetics and on mechanical properties of Fe40Ni40P10B6 and Fe5Co70Si15B10 amorphous ribbons — both pure and with defined impurities — was investigated by in‐situ tensile experiments in SEM. The effect of relaxation processes on tensile strength, microhardness and fracture toughness was analysed. A result of technological interest is the increase of fracture toughness after an annealing treatment in the temperature range Tann. = (0.55 … 0.6) · Tcryst.. This effect will be enhanced by defined chemical impurities, and it can be well interpreted by a model of fracture toughness variation during a temper process. In this model the deformation behaviour cannot be described within the scope of a homogeneous solid, but it is determined by a relationship between closely localized deformation instabilities.
Structure of the grain boundary region in an Al–15 at.% Zn and Al–2.0 at.% Zn–1.3 at.% Mg alloy aged at elevated temperatures
Authors: Syneček V. , Simmerska M. , Bartuška P. , Löffler H. , Gerlach R.
Published: January 2007

The results of TEM investigations are presented of the effects of various solutions and ageing treatments, cooling and quenching rates as well as of tensile stress at elevated temperatures on the microstructure of the grain boundary (GB) region of the examined AlZn and AlZnMg alloys.

A pronounced influence was found of partial coherency of GB stable β(Zn) precipitates with the α matrix in the AlZn alloy on the asymmetry of Zn depleted GB region and on the shape of GB precipitates. The role of GB's as sources and sinks of vacancies and the effect of stress gradients in GB regions were emphasized in the establishment of differences in the nucleation and decomposition characteristics within the GB region as compared to those within the grain interior. The existence of a negative stress gradient towards the GB has been suggested to lead to the observed gradual retardation of transformation kinetics within the GB region in AlZn alloys. A rapid quench from annealing to ageing temperature introduced large local stresses close to GB giving rise to “band of precipitates” on subsequent ageing within the former precipitate free region (PFZ) in AlZnMg alloy. Similar enhancement of local stresses accompanied by acceleration of decomposition kinetics was also observed in the aged AlZn sample subjected to a prior tensile creep exposure within the one‐phase region.
The use of an electrode potential in the investigation of a single‐crystal semiconductor matrix (I). On the nature of structural sensitivity of an electrode potential
Authors: Gulidov D. N. , Aidelman B. L. , Kwyatt N. A. , Chistyakov Yu. D. , Sverdlin E. A.
Published: January 2007

The fields of application of electrode potential measurement technique for the evaluation of structural perfection of single‐crystal semiconductor matrix are considered. The dependence of the silicon stationary potential on the value of elastic stresses in etching electrolytes is investigated. The structural sensitivity of the technique is confirmed by the investigation of planar anisotropy of mechanical damages due to the treatment of silicon wafers with (111) orientation and by the investigation of distribution of thermal elastic stresses in silicon — silicon dioxide interface.
Heteroepitaxy of ferrite‐spinel layers by CVD method
Authors: Aleksandrov L. N. , Mitlina L. A. , Molchanov V. V. , Vasilyev A. L.
Published: January 2007

The nucleation mechanism, the substructure, the inner stresses, and the formation of different dislocation structures were studied in the epitaxial ferrospinel layers. Monocrystalline layers of Mg‐Mn‐, Min‐ and Li‐ferrites were grown by the CVD method in a small gap on MgO substrates. The initial growth stage begins with the formation of three‐dimensional nuclei, but after their coalescence the mechanism of layer‐to‐layer growth is realized. X‐ray topographical study shows that the layer structure up to 6 μm thick was formed by slip steps but above 10 μm by cleavage steps. The residual elastic compressive stresses studied by X‐ray tensometry are about 6 × 108 N/m2. The development of dislocation structure of layers depending on their thickness and growth conditions was studied by means of optical and scanning electron microscopy: for synthesis temperatures up to 1200 K only the dislocation sliping was observed, above 1370 K their overcreeping occurred.
About the average bond ionicity in AIBIIIC compounds
Authors: Neumann H.
Published: January 2007

Average ionicities of the AIBIIIC2VI compounds are derived from the long‐wavelength electronic susceptibility and from the antisymmetric gap and the total width of the valence band. It is found that the ionicities determined in this manner are slightly larger than the arithmetic and geometric means of the individual bond ionicities are always below the critical ionicity value for the transition from tetrahedral to octrahedral coordination which explains the stability of the chalcopyrite structure in these compounds.
Growth of ammonium hydrogen tartrate single crystals in silica hydrogel
Authors: Desai C. C. , Hanchinal A. N.
Published: January 2007

Ammonium Hydrogen Tartrate (AHT) single crystals have been grown for the first time in silica hydrogel. The controlled reaction between tartaric acid and ammonium chloride solutions by diffusion process in gel medium has been employed. The colourless transparent AHT crystals upto 22 × 4 × 2 mm3 in size have been grown at room temperature. A brief description of the material preparation, growth procedure and crystal nucleation, have been given. X‐ray analysis showed that the AHT crystals belong to monoclinic crystal system. The average density of crystals measured pyknometrically and found to be 1.636 g cm−3. The effect of concentration of reactants on the growth and morphology of these crystals has been studied. The observations of the microstructures on the faces of these crystals revealed that they have been grown by layer mechanism. Chemical etching has been used to show the perfection of the crystals and implications are discussed.
Mathematical model of particle size distribution of crystals taking into account the growth dispersion
Authors: Baumann K.‐H.
Published: January 2007

This paper presents a mathematical model to describe the effect which the growth dispersion has on the particle‐size distribution of crystals which are formed in a crystallizer with an ideally mixed suspension and ideal product discharge (MSMPR crystallizer). This model starts from a number density distribution of crystals, which shows dependence on the process duration, the rate of crystal growth and the crystal size. The model differs from the diffusion model. The distribution data calculated are in agreement with distribution data measured and published by a number of other authors. The influence of the two parametersbandrLHon the mathematically determined frequency distributions is being studied.
The coprecipitation of magnesium nickel hydroxide solid solutions from aqueous solution: Precipitate compositions and precipitation mechanisms
Authors: Packter A. , Uppaladinni S. C.
Published: January 2007

Magnesium nickel hydroxides (solid solutions) were coprecipitated from different mixed metal cation solutions (overall concentration 0.1 M) and from hydroxide solution (0.1 M). The course of different coprecipitations was monitored by potentiometric (pH) titrations. Final Coprecipitate compositions were determined by chemical analysis, infra‐red spectrophotometry and thermal analysis. The ionic equilibria involved in different coprecipitations and the precipitation mechanisms are discussed.
Contribution of Z1‐centers in radiation hardening of NaCl: Sm2+ crystals — a study
Authors: Narasimha Reddy K. , Iqbal Ahmed Md. , Subba Rao U. V. , Hari Babu V.
Published: January 2007

Microhardness studies on X‐irradiated NaCl and NaCl:Sm crystals are studied with varying times of X‐irradiation in pre‐quenched and quenched crystals. The contribution of Z1‐centers in radiation hardening studies is discussed.
The role of impurity dispersion and hardness anisotropy studies in NaCl:Sm crystals
Authors: Narasimha Reddy K. , Subba Rao U. V. , Hari Babu V.
Published: January 2007

The effect of the distributed impurities and their state of dispersion on hardness of crystal is studied from microhardness measurements on NaCl crystals doped with different concentrations of samarium both in as‐grown state as well as after quenching them from various elevated temperatures. It is found that the small additions of impurity decrease the hardness. This has been explained on the basis of formation and dissolution of precipitates
Ionic conductivity of BaFBr
Authors: Somaiah K. , Hari Babu V.
Published: January 2007

The ionic conductivity of flux grown BaFBr crystals is reported. Measurements were made parallel to the crystallographic C‐axis in the temperature range 300 to 800 K. The ionic conductivity of the BaFBr pellet is found to be more than that of a single crystal. A tentative identification of low and high temperature conduction has been made as extrinsic association and extrinsic dissociation state of defect in the crystal while in pellet extrinsic dissociation and intrinsic regions. The probable mechanism for the conduction process has been discussed on the basis of structural considerations of the unit cell.
Linear growth of two‐phase regions during unmixing of NaCl‐KCl crystals
Authors: Andreev G. A. , Buritskova L. G.
Published: January 2007

Microscopic and flotation density investigations have been performed of unmixing in equimolar single crystals of NaCl‐KCl at elevated temperatures. The surface nucleation is found to be characteristic of the decomposition process. The two‐phase regions formed at the surface grow inward at a constant linear rate. The activation energy for the movement of the decomposition front is 0.9 eV at 180 to 260°C. The decomposition is anisotropic, <111> being the fastest unmixing direction. The decomposition zones nucleated on air bubbles inside the crystal tend to acquire a cube‐like form.
A study of complex glow curves of Quenched NaCl:Ca crystals
Authors: Narasimha Reddy K. , Nageshwer Rao C. , Lakshmipathi Rao M.
Published: January 2007

Glow curves of the thermally pretreated NaCl:Ca crystals are recorded and are found to be complex in nature. The complex glow curve is analysed using thermal cleaning technique and the trap parameters are calculated by various methods. The glow peaks have been tentatively attributed to impurity and various types of colour centers.
Crystal and molecular structure of p‐Toluquinone‐monoguanylhydrazone, C8H10N4O
Authors: Reck G. , Kretschmer R.‐G. , Schulze W.
Published: January 2007

The crystal structure of p‐toluquinone‐monoguanylhydrazone is orthorhombic, space group Pna21 with 4 formula units C8H10N4O in the unit cell. The lattice constants are a = 7.589, b = 20.117, and c = 5.699 Å. The structure was refined to the conventional R = 0.05. The configuration and conformation of the molecule as well as the unusual hydrogen bridge system are discussed.
Electron microscope studies of phase transformations in thin films of Tin Diselenide
Authors: Fernandez‐Samuel A. M. , Saxena U. , Srivastava O. N.
Published: January 2007

The present investigations explore the structural characteristics of the thin films of tin diselenide (SnSe2). Unlike bulk, only sparse studies are available on the structural characteristics in the thin form. SnSe2 is known to exhibit almost exclusively the 2H CdI2 type structure in bulk (single crystal) form. Particular emphasis on phase formation and structural transformations obtained in the thin film form has been given. The results reveal that all as‐deposited films are amorphous in nature and undergo an amorphous → crystalline transformation upon pulse annealing (∼200 °C), the crystalline phase exhibiting the 2H bulk structure. Further pulse annealing at higher temperatures (∼300 to 500 °C) results in thermal decomposition of this 2H phase, giving rise to several other phases, namely SnSe (orthorhombic), SnSe (cubic) and Sn2Se3 (tetragonal) phases, the SnSe phases exhibiting variations in lattice parameters. In addition, a new incommensurate phase of SnSe has been obtained. A model is proposed for the formation of this phase from the orthorhombie SnSe phase. The final product of decomposition is found to be tetragonal tin.
Structural defects and their genesis in corundum monocrystals
Authors: Dobrovinskaya E. R. , Litvinov L. A. , Pishchik V. V.
Published: January 2007

Besides the formation of dislocations and block boundaries behind the crystallization front, there is much experimental evidence indicating the presence of rather big aggregates in various crystal‐forming media. Experimental facts are given proving them to exist in Al2O3 melt. The perfection of a grown crystal depends on aggregation degree of the melt which can be controlled by both impurity cncentration and supercooling of the melt. E.g. in Verneuil‐grown crystals a change in Cr concentration from 1 ṁ 10=3 to 1% leads to a change in aggregate sizes from 100 to 1000 Å. With Stepanov‐, Czochralski‐, and horizontally directed crystallization methods a variation in supercooling the melt enables to change the size of the aggregates from 150 to 400 Å. High values of the diffusion coefficient are accounted for by a higher concentration of the holes. The main reason increasing the number of holes in the crystals grown by the mentioned methods is the presence of the boundaries between incoherently accreted aggregates.
Influence of lateral branches on the properties of liquid‐crystalline 1,4‐Bis‐[4‐n‐hexylbenzoyloxy]‐2‐subst.‐benzenes (I).: measurement of density, viscosity and optical anisotropy
Authors: Hauser A. , Rettig R. , Selbmann Ch. , Weissflog W. , Wulf J. , Demus D.
Published: January 2007

8 compounds of the substance class of the 1,4‐bis‐[4‐n‐hexylbenzoyloxy]‐2‐subset.‐benzenes

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and additionally 1,4‐bis‐[4‐n‐hexyleyclohexanoyloxy]‐2‐ethylbenzene were sythesized and density, viscosity and optical refractive indices were measured in the nematic and isotropic state. The lateral branching causes decrease of the melting and clearing temperatures, diminishing of the optical anisotropy and order parameter, but increase of the viscosity.
Concentration dependence of the electron diffusion length in p‐type GaAs
Authors: Vigil E. , Diaz P.
Published: January 2007

The concentration dependence of the electron diffusion length in p‐type GaAs is analyzed based on experimental values reported in the literature and recent studies of minority carriers mobility in GaAs. The dependence of Ln with doping impurity concentration is determined for τnr ≫ τr and good agreement is found with highest reported experimental values of Ln; considerations are made about τnr. The dependence of electron mobility, diffusion constant, and radiative recombination lifetime on concentration are also given.
Asymmetry of isolated dislocation mobility in Silicon single crystals
Authors: Nikitenko V. I. , Farber B. Ya. , Yakimov E. B.
Published: January 2007

The main quantitative characteristics of asymmetry of isolated dislocation mobility in Si single crystals manifested in an essential difference (up to an order of magnitude) of the velocities of broadening and narrowing dislocation half‐loops have been investigated. Transition from broadening to narrowing of the dislocation half‐loop is found to result in the nonmonotonic temperature dependence of the 60° segments velocities as well as in changing the stress dependence of the velocity. The high temperature annealing of the sample befor the reversal of the dislocation glide is found to cause the asymmetry disappearance. The analysis of the results obtained is performed. It is concluded that the phenomenon observed may be due to a rearrangement of the point defect structure during the course of the dislocation glide.
Quantum effects in low temperature plastic deformation
Authors: Labusch R.
Published: January 2007

A quantum mechanical calculation of the transition rate of a dislocation segment across an obstacle of finite width is performed. Compared with previous theories the achievement of the new treatment is that the finite compliance of the force distance profile is taken into account in the evaluation of the oscillatory modes. As a consequence, not only the DEBYEtemperature of the dislocation line but also the obstacle compliance enters the transition rate and determines the temperature regime in which quantum effects become observable. Furthermore, the results of classical thermal activation theory that is valid at high temperatures are for the first time derived from first principles.
Screw dislocation core structure and plastic deformation of BCC Metals
Authors: Kuramoto E. , Aono Y. , Tsutsumi T.
Published: January 2007

The core structure and an energy distribution around a screw dislocation core in model bcc lattice have been investigated in both unstressed and stressed states to clarify the controlling factors which determines the core type and the shape of PEIERLS potential. In the case of iron total four types of core structure were obtained, namely, unpolarized, polarized, split and high energy position and the shape of PEIERLS potential was so‐called camel hump type which gives a steadfast explanation for the presence of a hump on the yield stress — temperature curve of iron single crystal. The calculated results for the spatial distribution of the PEIERLS potential around a core show that the range of distribution is relatively small in the low PEIERLS stress case (iron), but is large in high PEIERLS stress case (vanadium).
Thermally activated deformation of Alpha Zirconium
Authors: Trojanová Z. , Lukáč P.
Published: January 2007

The effect of temperature on the yield stress of polycrystalline α‐zirconium has been examined at temperatures between 77 and 900 K. A strong temperature dependence of the yield stress (interrupted in the temperature ranges 300 to 400 K and 500 to 700 K where the yield stress is independent of temperature) indicates the occurence of the thermally activated processes during deformation. The activation volume at the onset of deformation has been determined as a function of temperature in the range 77 to 523 K.
On the morphology of <100>‐textured Germanium Crystallites in Zn—Ge Eutectic Alloy
Authors: Vetter JÖRg , Frühauf Joachim , Schneider Helmut GÜNther
Published: January 2007

Different geometry parameters for the cross‐like germanium crystallites (eutectic dendrites) of the Zn‐Ge eutectic alloys unidirectionally solidified have been related to the growth rate R and liquid temperature gradient G using linear regression analysis. It has been found that for eutectic dendrite spacing λ, balk length d and balk thickness b follow the relationship of the type w = CwR−rwG−gw; Cw is a constant. The spacing relationship of eutectic dendrites (rλ = 0.21; gλ = 0.48) shows a similarity with published experimental and theoretical results on primary dendrite arm spacing (rλ = 0.25; gλ = 0.5). It has been shown in terms of a profile ration λ/d that for geometrical similar morphologies the relationship λ2R = const. is valid.
Pearson plot of chalcopyrite type (E11), phases
Authors: Paufler P. , Rotsch P.
Published: January 2007

Linear equations are obtained from a hard sphere model that relate the unit cell dimensions of E11 compounds to the atomic diameters for coordination number 4. They are compared with experimental data for 36 compounds. So, the explicit identification of the atomic arrays that control the lattice parameters a and c can be performed.
Studies on syntactically coalesced Silicon Carbide polytype structures
Authors: Singh S. R.
Published: January 2007

The structure of two new silicon carbide polytypes, found in syntactic coalescence with a basic structure 6 H, have been worked out. The structure of polytype 21 H is [(33)263] and that of polytype 93R is [(33)434]3. The polytype 93R belongs to the structure series [(33)n34]3. One of the (00.1) growth face reveals the growth spiral. The splitting of diffraction spots indicates the existence of a high period polytype in the crystal. This high period polytype have been identified as 558H or 1674R. The growth mechanism have been discussed in the light of above observations.
Study relating to temperature stability of the Natural Laumontite Zeolite
Authors: Rykl D. , Pechar F.
Published: January 2007

On the basis of the DTA measurements, the natural laumontite zeolite has been subjected to thermal decomposition at temperatures of 20, 250, 420, 580, 750, and 1000°C. The decomposition products were identified by the X‐ray powder method (CuKα‐) and IR spectroscopy (Nujol). It has been determined that the crystal structure of laumontite is stable up to the temperatures of 250°C. The dehydration of the mineral that takes place has three phases. With the increasing temperature, besides the conserved laumontite basic lattice (up to 420°C), a new phase “X” (paraleumontite) is produced. At 1000°C the laumontite is transformed in anorthite. The following phenomena correspond to dehydration: The intensity decrease of the OH stretching vibration, vanishing of librations and H2O bending vibrations. The remaining water is hydrolytically split up and forms structural OH‐groups which partially outlast up to 1000°C.