bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron microscopic investigations of precipitates in doped NaCl crystals
Authors: Raju I. V. K. Bhagavan
Published: January 2007

Precipitation morphology of NaCl:CdCl2 and NaCl:SrCl2 crystals is investigated by high voltage transmission electron microscopy. The volume fraction of the precipitates and the content of CdCl2 has been evaluated using the theory developed by Hillard. Selected area diffraction patterns of the precipitates and investigations of the misfit dislocations around the precipitates is presented.
Dislocation activity in single crystals of stannic iodide
Authors: Desai C. C. , Rai J. L.
Published: January 2007

Single crystals of stannic iodide (SnI4) have been grown employing the controlled‐reaction between SnCl2 and KI solutions by diffusion process in silica gels. As‐grown (111) surfaces of the crystals have been optically studied. Characteristic growth spirals and hopper growth patterns have been observed on them. By successively etching (111) surfaces in a 0.2 N HCl solution, it is established that the pits indicate the sites of dislocations in the crystals. This is further confirmed by comparing the etch patterns before and after chemically polishing (111) surfaces. The average dislocation in the SnI4 crystals have been determined and found to be 7.3 × 102 cm−2. Observations of polygonisations are described and the implications are discussed.
Investigation of the nature of point defects in in Te‐doped gallium antimonide
Authors: Wilke J. , Bublik V. T. , Osvenskii V. B. , Popkov A. N. , Braginskaya A. G. , Kolchina P. P.
Published: January 2007

Precision lattice constant and density measurements held on gallium antimonide single crystals grown from stoichiometric melts showed that doping of such crystals with Te lead to the intensification of Ga‐supersaturated solid solution decomposition process with initial Frenkel defect (Gai + VGa) production. It is supposed that Tesb — simple donors form complexes with VGa which are believed to be acceptors. Doping of GaSb with Te up to the levels above 2 · 1018 cm−3 leads to partial decomposition of GaSb(Te) solid solution supersaturated with Te.
Vacancy formation enthalpies in AIBIIIC chalcopyrite semiconductors
Authors: Neumann H.
Published: January 2007

Formation enthalpies ΔHv of single vacancies in all AIBIIIC2VI chalcopyrite structure compounds are estimated using the macroscopic cavity model. A comparison with atomic sublimation enthalpies ΔHsub of the BIII and CVI atoms derived from existing partial vapour pressure data shows that within the accuracy of this data and the theoretical calculations the relation ΔHv ⪆ ΔHsub is fulfilled as expected from general considerations.
Cathodoluminescent efficiency of Y3Al5O12 and YAlO3 single crystals in dependence on Ce3+ and other dopants concentration
Authors: Autrata R. , Schauer P. , Kvapil Jo. , Kvapil Ji.
Published: January 2007

The content of Ce3+ ions in the investigated single crystals grown under reducing conditions is limited by a low value of the distribution coefficient. This distribution coefficient decreases sharply with increasing concentration of Ce3+ ions in a melt. Cathodoluminescent efficiency rises with increasing Ce3+ concentration up to a certain state of saturation. At higher concentrations of Ce3+ ions emission from activator centres is dominant, while at lower concentrations defect centres play an important part. Iron acts as a strong quenching centre, especially in the YAlO3 lattice. Nd, Ir, Fe, Ti, Cr centres exhibit a high quenching effect, too. A trace amount of Mo enhances cathodoluminescent efficiency.
Chiral SmC* liquid crystals obtained by mixing of SmC and cholesteric phase
Authors: Pavel J. , Glogarová M. , Demus D. , Mädicke A. , Pelzl G.
Published: January 2007

The binary mixtures of the substance magnified image providing cholesteric phase exhibit a chiral SmC* phase for certain concentration and temperature range. This phase was verified to be ferroelectric. The temperature dependences of the spontaneous polarization and the coercive field were determined for three concentrations. The pitch of the helical structure is approximately indirectly proportional to the molar concentration of the cholesteric substance and varies from 3 μm to about 25 μm in the concentration range from 20 mol% to 5 mol% of the cholesteric substance. For the lower concentrations the sample is unwound in planar samples due to the surface anchoring. Two possible unwound planar configurations can be switched by electric field.
Copper precipitation in long‐time processed transistor samples
Authors: Gleichmann R. , Breitenstein O. , Mohr U.
Published: January 2007

Process‐induced crystal defects (point defects and extended defects) in completely processed transistor samples of floating zone silicon have been investigated by TEM analysis and DLTS measurements. It was possible to demonstrate that the lifetime of these samples is determined by the introduction of copper during the long‐time processing of the wafers. The predominant crystal defects within the wafer volume were found to be circular monolayers of copper silicide which due to their appearance could be easily confounded with stacking faults.
X‐ray and scanning cathodoluminescence imaging of small‐angle grain boundaries and dislocations in CdTe crystals
Authors: Klimkiewicz M. , Auleytner J.
Published: January 2007

By employing the Reflection X‐ray Topography (RXT), on one hand, and the Cathodoluminescence (CL‐IR) mode of operation of the Scanning Electron Microscope, on the other hand, wer are able to visualize the lattice defects in CdTe single crystals. The possibility of defect identification is the advantage of the RXT technique. Moreover, the examined surface can be imaged as a whole. Cathodoluminescence, however, guarantees higher resolution. The defects in CdTe crystals, observed in cathodoluminescence images, have been identified as small‐angle boundaries and screw dislocations.
Dependence of refractive indexes dispersion for LiNbO3 on impurity
Authors: Bodnar I. T. , Yarunichev V. P.
Published: January 2007

The effect of the impurities of the transition metals Co, Mn, Cr, Fe, Ni, Cu on the dispersion of the refractive indexes of LiNbO3 is studied. The dispersion curves for LiNbO3 are compared to those for the pure crystals. The relation between the difference of the refractive indexes of the pure and doped LiNbO3 and the ionic radius of the impurity is established.
Electrical properties of ZnO single crystals annealed in a zinc atmosphere
Authors: Ziegler E. , Heinrich A. , Oppermann H. , Stöver G.
Published: January 2007

The electrical conductivity and the Hall coefficient of ZnO single crystals annealed in a zinc atmosphere after growth were measured in a temperature range from 77 K to 1000 K. The results are compared with those of ZnO crystals from the zinc rich phase boundary. A shallow level with an activation energy at about 15 meV dominates in both groups of samples. Its concentration was found to correlate directly with the degree of non‐stoichiometry.
Structure refinement of an 1M‐lepidolite
Authors: Backhaus K. O.
Published: January 2007

The structure of an 1M‐lepidolite from Wakefield (Canada) has been investigated by X‐ray diffraction structure analysis. The refined atomic coordinates and occupation factors indicate an ordered distribution of the octahedrally coordinated cations. The structure has the space group C 2. The tetrahedra do not show any remarkable ordering of their central cations. Octahedral flattening is characterized by a mean octahedral angle of 58.66°. The tetrahedral rotation angle is equal to 5.9°.
EPR studies on Mn2+ centres in solid solutions of TSCC and TSCB
Authors: Küchler J. , Malige B. , Meister R. , Triebeneck R. , Windsch W.
Published: January 2007

EPR investigations of Mn2+‐doped solid solutions of TSCC and TSCB were performed between 130 K and 300 K. The axial fine structure parameter D vs bromine concentration x is nonlinear. The relation between the axial fine structure parameter and bromine concentration is discussed by means of a simple statistical model.
Application of the iodide synthesis to the preparation of indium arsenide bulk crystals and epitaxial layers
Authors: Trifonova E. F. , Karagiozov L. , Hitova L.
Published: January 2007

Bulk crystals and epitaxial layers have been prepared from iodidely synthesized InAs. Their parameters have been studied and compared with those of high‐temperature synthesized InAs. The synthesis mixture composition substantially effects the electrical parameters of the samples. Iodine is supposed to be a donor‐acting impurity in iodidely synthesized InAs.
Mechanism of chemical dissolution of calcite in lactic acid
Authors: Bhagia L. J. , Pandya J. R.
Published: January 2007

Effect of etching time and temperature on morphology of etch pits and etch rates in controlled dissolution of calcite by lactic acid it optically investigated in detail. Arrhenius equation is used to determine activation energy which is observed to change with the morphology of etch pits. Further, an attempt is made to understand the mechanism of dissolution by considering Laidler's theory of heterogeneous catalytic reactions.
A study of Z1‐centers in γ‐irradiated KCl:Ba2+ crystals
Authors: Reddy K. Narasimha , Rao U. V. Subba , Babu Hari
Published: January 2007

The purpose of the paper is to report the optical absorption and thermoluminescence measurements on KCl: Ba2+ crystal irradiated with γ‐rays. Bleaching in F‐band increases the glow peak around 75 °C and suppresses the 125 °C peak. A similar result is observed in preheat treated crystals. When this peak is thermally cleaned, the broadening of the absorption on the prolonged F‐bleached crystals is removed. On the basis of these observations, the glow peak at 75 °C is tentatively attributed to Z1‐centers.
I–V characteristics and break down studies of Sb2O3 structures
Authors: Kumar J. Siva , Narayana G. , Shekar M. Chandra , Rao U. V. Subba , Babu V. Hari
Published: January 2007

I–V characteristics of sandwiched Al–Sb2O3–Al structures have been studied for different thicknesses. The current‐voltage curves in general exhibit three regions, ohmic, non ohmic and breakdown regions. The breakdown voltage increases whereas the dielectric strength decreases with increase in Sb2O3 film thickness. The electrical breakdown studies have been done for dc and ac voltages and optical photomicrographs of breakdown patterns during different stages of voltage have been taken and the results are explained.
Electrical characteristics of GaAs LPE schottky diodes
Authors: Konakova R. V. , Tkhorik Yu. A. , Zaitsevskii I. L. , Benč V. , Morvic M. , Kordoš P. , Červenák J.
Published: January 2007

Structural and electrical properties of IMPATT diodes prepared from homoepitaxial GaAs films grown by liquid phase epitaxy have been investigated with the help of metallography and reverse I–V characteristic derivatives. The structural defects in epitaxial layers have been shown lead to the localization of current in separate regions (microplasmas) which brings up a soft breakdown. A method as been proposed for the observation of microplasmas at large currents.
Growth and structural characteristics of the chalcopyrite semiconductor CuInSe2
Authors: Janam Ram , Srivastava O. N.
Published: January 2007

The growth and structural characteristics of chalcopyrite semiconductor CuInSe2 have been investigated with particular emphasis on the photovoltaic behaviour of the CdS/CuInSe2 thin film heterojunction. It has been found that the structural phase of the CuInSe2 has an important bearing on the photovoltaic behaviour of the heterojunction. Thus the heterojunctions having the sphalerite type cubic CuInSe2 as one of its component have been found to possess better conversion effciency than those employing the chalcopyrite type tetragonal form of CuInSe2. Evidences and argument have been put forward to show that the better efficiency with sphalerite phase arises due to smaller lattice mismatch with CdS base. In addition to the type of structural phase, the state of order of CuInSe2 phase has been found to affect the performance of heterojunctions. The heterojunctions having the disordered sphalerite type CuInSe2 structure exhibits a much lower efficiency than those embodying the ordered CuInSe2 phase.
Doping process control in silicon epitaxy (I). System identification
Authors: Kósza G. , Morgenstern T. , Richter F. , Valkó P.
Published: January 2007

The transition behaviour of the phosphorus incorporation in silicon epitaxial layers grown in a CVD reactor has been investigated, considering the reactor as a linear control system with u = lg p0PH3 (t) as the input and y = lg N(t) as the output. The response of system to both upward and downward step inputs has been studied experimentally, using SiH4 and PH3 sources. The dopant system of a horizontal silicon epitaxial reactor has been identified and a mathematical model relating to the transient behaviour of the system has been found. The parameters of the model have been estimated from layer growth experiments. The step response functions found can be approximated by an exponential function relating to n time constants T, all equal to each other. It was found for the system investigated that the second order model is of sufficient accuracy for the optimal control calculations described in the next part of this series.
X‐ray double crystal diffractometer for testing of plane analyser crystals of LiF
Authors: Dressler L. , Wehrhan O.
Published: January 2007

A double crystal diffractometer (DCD) for testing LiF crystals is presented. It is possible to distinguish in a relatively short measuring time (nearly 10 minutes including change of sample and adjustment) between crystals with block desorientation angles >1′ and ≦ 1′ (1′ = 0.291 · 10−3 rad). The extention of area registered during a measurement depends on the kind of section of crystal and the kind of reflection; at the examination of {100}‐cleavage faces of LiF an elliptical area of a height of 15 mm and a length of 115 mm is registered.
Lattice disorder and optical absorption of PbTiO3 crystals
Authors: Bollmann W. , Wehrhan G.
Published: January 2007

The electric conductivity and the optical absorption of PbTiO3 crystals are explained by the existence of Pb3+ ions and free holes as electronic defects and of O– vacancies and interstitials as ionic anti‐Frenkel defects. The absorption band at 475 nm is caused by Pb3+ ions and produces the yellowish or brownish colour of the crystals. Using fluoridic fluxes instead of oxidic fluxes for the crystals growth a small part of O– ions is replaced by F− foreign ions. This substitution diminishes the Pb3+ ion content and causes an increased optical transmission of the PbTiO3 crystals.
Single crystals of barium substituted rare‐earth orthomanganites
Authors: Nevřiva M. , Pollert E.
Published: January 2007

The single crystals from the series of Re1‐xBaxMnO3solid solutions (Re = Pr, Nd) were prepared by the flux growth from the melt containing 0.41 BaO — 0.18 BaF2— 0.41 B2O3. as the flux constituents. The conditions of the growth, in particular the liquidus curves of the relevant pseudobinary systems, were determined by the high‐temperature microscope technique. The prepared crystals were characterized by X‐ray and chemical analysis.
Rotation field and continuity equation for texture evolution
Authors: Wierzbanowski K. , Clement A.
Published: January 2007

In the present paper a quite general approach is proposed for the problem of the formation of the prefered orientations (i.e. of the texture). The rotation field is considered by the present authors as the most general variable which describes completely the texture formation process. The proposed continuity equation transforms immediately the rotation field to the texture function (Orientation distribution function). The presented formatlism is illustrated by a few f.c.c. rolling textures.
Conoscopic optical method of determining liquid crystal low tilt angles
Authors: Komitov L. , Hauck G. , Koswig H. D.
Published: January 2007

A simple conoscopic optical method of determining liquid crystal low tilt angles with sufficient accuracy for many practical purposes is described. The similarity between this method and the crystal rotation one is shown. The limits of applicability of the conoscopic optical method are also given.
The influence of OH−‐ions on the mechanical properties in LiF and NaCl single crystals
Authors: Lubenets S. V. , Ostapchuk E. I. , Soifer L. M. , Appel F. , Kaufmann H.‐J.
Published: January 2007

An LiF‐ und NaCl‐Einkristallen wurde der Einfluß der Atmosphäre beim Wachstumsprozeß auf die Verformungseigenschaften untersucht. Die Atmosphären waren Luft oder Vakuum bzw. Argon. Die an Luft gezogenen Kristalle haben in einem breiten Temperaturintervall eine höhere Fließspannung und ein kleineres Aktivierungsvolumen. Außerdem ist die Versetzungsbeweglichkeit geringer. Die Unterschiede entstehen vermutlich durch OH−‐Ionen, die in den an Luft gezogenen Materialien in größerer Konzenration gefunden wurden. Die OH−‐Ionen können selbst Gitterverzerrungen erzeugen bzw. durch die Zusammenlagerung mit den zweiwertigen Kationverunreinigungen bilden. Auf diese Weise erhöht sich die Dichte der thermischen und athermischen Hindernisse für die Versetzungsbewegung.
Characteristic temperature of deformation of crystalline materials
Authors: Trefilov V. I. , Milman Yu. V. , Gridneva I. V.
Published: January 2007

Using the ceoncept of a characteristic deformation temperature, t* (knee temperature), below which the PEIERLS‐NABARRO stress becomes significant, some general regularities have been determined on the influence of temperature upon structural state and mechanical properties of crystalline materials. It is demonstrated that t* represents a natural boundary between the intervals of warm and cold deformation. At the temperature t*, the mechanisms of deformation, fracture, and recovery of properties in annealing vary significantly in the same manner for different crystals.
Induced growth striations in Quartz Crystals
Authors: Bernhardt Hj. , Alter U.
Published: January 2007

Due to periodical modulation of the temperature difference between the solution and growing rooms growth striations in quartz crystals have been induced. These induced striations have been found as smoky quartz coloration striations as Al containing material has been used. X‐ray topographic investigations found these growth striations even in the unirradiated quartz crystal.
Liquid‐phase epitaxy of Potassium Niobate
Authors: Khachaturyan O. A. , Madoyan R. S.
Published: January 2007

The possibility of potassium niobate films growing by means of liquid phase epitaxy technique was investigated. The physical and chemical analyses of K2O‐V2O5‐Nb2O5 system were carried out. Corundum wafers with {1¯210} and {0001} orientations served as substrates. The grown films were 10–30 μm thick. The grown heterostructures had a sharp, phase boundary line substrate‐film. Epitaxial layer perfection was investigated by X‐ray and electronographic methods.
Effect of γ‐irradiation on mechanically activated and on non‐activated LiF
Authors: Eifler R.‐J. , Ebert I. , Hennig H.‐P. , Schmidt J. , Kretzschmar U.
Published: January 2007

By means of EPR spectroscopy lattice defects have been investigated, which had been produced in OH− containing LiF by mechanical activation and subsequent irradiation (mainly γ‐irradiation). The structure of irradiation‐induced hydrogen centers shows characteristic differences dependent on the kind of LiF: Hs0 (hydrogen atoms in anion vacancies) are created in mechanically activated LiF powders, whereas Hi0 (hydrogen atoms in interstitial positions) in LiF single crystals. In both the cases also F centers are produced besides other paramagnetic defects. The observed defects can be used for an estimation of the degree of distortion in mechanically activated LiF.
Plasticity of high purity iron single crystals (I) 1. work hardening
Authors: Novák V. , Kadečková S. , Šesták B. , Zárubová N.
Published: January 2007

High purity iron single crystals were deformed in tension in the temperature range 4.2 to 473 K. Work‐hardening characteristics were determined and the plastic behaviour in dependence on temperature, strain rate and crystal orientation isz discussed. The transition temperature between low‐temperature and intermediate‐temperature deformation regimes was found to be ≅ 250 K, the critical temperature estimated from the temperature dependence of the critical resolved shear stress is ≅ 380 K. A hump on the temperature dependence of the critical resolved shear stress was observed in the vicinity of 250 K. These observations are qualitatively explained by special mobilities of dislocations in b.c.c. lattice.
Crystal growth of PbTe and (Pb, Sn)Te by the bridgman method and by THM
Authors: Gille P. , Mühlberg M. , Parthier L. , Rudolph P.
Published: January 2007

Synthesis and growth of PbTe and (Pb, Sn)Te single crystals by the Bridgman method and by the Travelling Heater Method (THM) from Te‐rich solutions are described. It is to be seen from comparative investigations that seeded THM growth reproducibly provides oriented single‐crystalline ingots free of low‐angle grain boundaries and with etch pit densities of 8–12 × 104 cm−2. All the materials were p‐type with carrier concentrations from 1 to 2 × 1018 cm−3.
Process characteristics and parameters of Anodic Oxidation by spark discharge (ANOF)
Authors: Krysmann W. , Kurze P. , Dittrich K.‐H. , Schneider H. G.
Published: January 2007

Process characteristics and parameters of ANOF as well as that special logarithmic relation of the layer formation parameters which is valid for the spark region are discussed. By calorimetric investigation it can be shown that the greatest share of electric energy will be transformed to heat and that the current quantity of ≈ 1.1.A · s · cm−2 is characteristic for the incubation period before spark discharge during the gas — solid reaction of aluminium coating.
The fracture behaviour of Chromium‐ and Titanium‐doped sapphire monocrystals
Authors: Müller B.
Published: January 2007

The influence of chromium and titanium on the fracture behaviour of sapphire crystals was analysed by means of crack indentation pattern, and the critical stress intensity factors for the easiest spalling planes of the sapphire were measured from the crack lengths at the indents. Together with information on the room temperature plasticity of sapphire the results allow conclusions on the influence of the dopants on crystallographic and glass‐like fracture features, respectively.
Effective oxygen charge in SiO2 and its dependence on the bond angle of oxygen
Authors: Geisser C. H. , Hübner K.
Published: January 2007

It is not clear until now, whether the oxygen bond angle and the effective oxygen charge in SiO2 are correlated or not. This paper reviews various theoretical and experimental facts concerning some special features of the atomic structure and of electronic properties of SiO2. They lead to contrary conclusions about the correlation between the effective oxygen charge and the oxygen bond angle in distinct SiO2 forms. Results basing on quantum‐chemical investigations are compared with conclusions drawn from the dielectric theory and from tight‐binding calculations of electronic states. A critical valuation of the different methods with special consideration of solid‐state investigations yield the result that the effective oxygen charge increases with increasing bond angle.
Crystal growth rate from the AgNO3‐Dimethylsulfoxide melt
Authors: Pacák P. , Špalková H.
Published: January 2007

The growth rate of AgNO3·DMSO crystals from its melt and concentrated aqueous solutions was studied in the dependence on supercooling (ΔT = 0.5–65°C) by microscopic technique. The experimental results were analyzed according to the formalism proposed for describing growth kinetics from melts.
The growth of oxide precipitates during intrinsic getter formation
Authors: Pekarev A. I. , Nemtsev G. Z.
Published: January 2007

The simulation of the process of the intrinsic oxide getter (IOG) formation in terms of the precipitate growth depending on oxygen concentration in single‐crystal silicon and the nucleation temperature is done. The conditions of annealing at continuously increasing temperature and those of two‐stage and isothermal anneals are calculated. The possibility of intrinsic getter formation in Si with the boron concentration of 1.1015 and that of oxygen 6–8.1017 cm−3 during a two‐step annealing is experimentally evaluated (according to the density of microdefects). The temperature of the most rapid growth of IOG predicted due to the simulation is defined.
Effective distribution coefficient of Si in Fe—Si alloys at floating zone melting
Authors: Vaněk P.
Published: January 2007

Effective distribution coefficients of silicon in Fe—Si alloys with 1.0–12.1 at.% Si in floating zone melting at various solidification rates were determined. The dependence of kef on the solidification rate was compared with the Burton‐Prim‐Slichter equation. Effective distribution coefficients extrapolated to a zero solidification rate were compared with equilibrium distribution coefficients taken from the equilibrium phase diagram of Fe—Si.
The Proton‐induced kossel effect and its application to crystallographic studies
Authors: Geist V. , Ascheron C.
Published: January 2007

A survey is given of the characteristic features of the proton‐induced Kossel effect and its use for crystallographic investigations of semiconductor materials. The excitation of the characteristic X‐rays was performed with protons in the energy range 0.5–1.5 MeV. Mainly long‐wave X‐radiation was used because of the high X‐ray yields and large Bragg angles also for reflections with low indices. The use of the effect for lattice parameter determinations, the identification of polar surfaces and the detection of tetragonal distortions is described. In this connection the advantage of simultaneously recording Kossel reflection and blocking pattern is also demonstrated. The different behaviour of the observed P—Kα‐ and Ga—Kα‐reflections in response to lattice damage is pointed out.
Electrical properties of Al‐CeO2‐Al thin film capacitor structures
Authors: Chandra Shekar M. , Hari Babu V.
Published: January 2007

Cerium Oxide films were prepared by vacuum thermal evaporation from tantalum boat in a conventional vacuum coating unit. Current‐voltage characteristics were studied for different film thicknesses. The breakdown voltage (VB) and dielectric field strength (EB) were calculated. It is found that the breakdown voltage increases and dielectric field strength decreases as the thickness of the film increases. The applicability of Forlani‐Minnaja relation is discussed. Current‐voltage characteristics were also drawn at different temperatures and breakdown voltages were calculated. The breakdown voltage decreases as the temperature of the structure increases but the variation is nonlinear. The variation of current density with temperature was studied and the activation energy for the migration of charge carriers was calculated and it is about 0.52 ev. The results were discussed.
Thermoluminescence of ZnO:Cu, La under UV and γ‐ray irradiation
Authors: Diwan D. , Bhushan S. , Kathuria S. P.
Published: January 2007

Thermoluminescence (TL) glow curves of ZnO: Cu, La have been recorded under UV and γ‐ray irradiations. These consist of a pronounced peak at 600°K alongwith some sharp transitions. The higher temperature peak has been studied by a number of methods namely heating rate, initial rise, isothermal decay and peak shape methods and activation energy (E), escape frequency factor (s) and the order of kinetics (l) have been determined and their nature has been discussed. E is found to be ∼1.63 eV and the order of kinetics l = 2 for this peak.
Formation of iron carbonitride and iron carbide phases during nitrogen ion implantation
Authors: Rauschenbach Bernd , Hohmuth Karl
Published: January 2007

Polycrystalline iron is implanted with nitrogen ions with high doses at room temperature. During nitrogen ion implantation iron is doped with carbon by recoil implantation. The formation and the transformation of iron carbonitrides and iron carbides are investigated by high‐voltage electron microscopy. The implantation‐induced phase formation of iron carbonitride phases are discussed.
Peculiarities of the cross‐section in chemically prepared SnO2‐ and SnO2:Sb layers
Authors: Dogil B. , Froissart F. , Horodecki A. J. , Precht W.
Published: January 2007

Layers of pure as well as Sb‐doped tin dioxide have been prepared using intentionally simple modification of CVD technique. By electron microscopy of cross‐section, at least two sublayers have been observed in samples of thickness of a few micrometers in both of the cases. Their formation is thought to be associated with small perturbation of thermodynamical equilibrium arising due to the layer growth.
The effect of B2O3 on the solubility of (YSmLuCa)3(FeGe)5O12 garnet in PbO‐B2O3 flux
Authors: Nitsch K. , Bok J. , Kučera M. , Petrík S. , Pištora J. , Višňovský Š.
Published: January 2007

The paper deals with the solubility of (YSmLuCa)3 (FeGe)5O12 garnet in PbO—B2O3 flux. An anionic model explaining the effect of B2O3 on the solubility of rare earth garnet is suggested. This model is based on the assumption that PbO in the melted mixture of PbO, B2O3, Fe2O3, R2O3, CaO, GeO2 dissociates into Pb2+ and O2−. The oxygen anions react with the other oxides under the formation of BO33−, FeO33−, RO69−, CaO22− and GeO32− anions, until the equilibrium is established. The garnet is dissociated into the anions mentioned above. The validity of the model is verified by an agreement of the experimentally determined saturation temperatures of the melts for LPE of garnet layers with the Arrhenius‐type expression of the solubility product of garnet
magnified image
where xi denotes the equilibrium concentrations of the anions in the melt and x° is the Ge content of the garnet film.
X‐ray investigations of BaLaGa3O7 single crystals
Authors: Przedmojski J. , Pura B. , Piekarczyk W. , Berkowski M.
Published: January 2007

X‐ray investigations have been carried out on single crystals of BaLaGa3O7. Debye temperature as well as thermal expansion coefficients were determined, and values of which are respectively
Neutron diffraction topography of crystals with highly misorientated regions
Authors: Chalupa B. , Vrána M. , Kulda J. , Lejček P.
Published: January 2007

By means of neutron topography the single crystals with highly misorientated regions were imaged.
The role of impurity precipitates on microhardness of NaCl:Ba2+ crystals
Authors: Narasimha Reddy K. , Lakshmipathi Rao M.
Published: January 2007

Microhardness studies of NaCl crystals doped with different concentrations of barium have been carried out both in the as grown state and after quenching them from various elevated temperatures. In heavily doped NaCl crystals visible precipitates are observed and after quenching these precipitates are dissolved partially. The effect of these precipitates on microhardness is discussed.
Nucleation and growth of some solution‐grown crystals in gel media: Visualization by interferometric holography
Authors: Lefaucheux F. , Robert M. C. , Bernard Y. , Gits S.
Published: January 2007

Holographic interferometry has been applied to the study of mass transfer induced by nucleation and growth in gel media. Real time obsrvations were made on growth of insoluble (CaHPO4, 2 H2O) and soluble (KDP) materials.
Some transport measurements of WSe2‐x single crystals
Authors: Agarwal M. K. , Jani A. R. , Kshtriya J. D. , Vashi M. N. , Garg P. K.
Published: January 2007

Electrical resistivity and its anisotropy, thermoelectric power and temperature coefficient of resistivity of WSe2‐x crystals have been measured (0.01 ≦x≦ 0.1) in the temperature range 300–448 K. Variations of these physical properties with respect to temperature and composition have been examined. The observed results are discussed in the light of semiconducting nature of the material.
VSZ‐5 Zeolite crystals — hydrothermal synthesis and characterization
Authors: Joshi M. S. , Mohan Rao P. , Choudhari A. L. , Kanitkar Ravindra G.
Published: January 2007

Procedure for hydrothermal synthesis of zeolite crystals, named here as VSZ‐5, is described. Needles, prismatic and prismatic pyramidal habits of these crystals are illustrated and described. By Mössbauer spectroscopy it is established that iron is leached out from the steel liner used. Phosphorus is introduced in the zeolite lattice. Surface structures on the crystals are illustrated.
Structure investigations of the Ge‐GeO2 system by high‐resolution electron microscopy
Authors: Werner P. , Rozhanski N. V. , Arslambecov A. V. , Heydenreich J.
Published: January 2007

The crystal structure of thermally oxidized Ge was investigated by high‐resolution electron microscopy (HREM), mainly the interface Ge/oxide. Under special conditions the reaction Ge + O2 → GeO2 which takes place at (111) surface planes leads to suitable thin crystal regions. The GeO2 occurs normally as amorphous films on the crystal surface. Furthermore, hexagonal GeO2 can grow at the interface Ge/oxide by a topotaxial reaction; the orientation relation between these two lattices was ascertained. Intensive electron irradiation was used to initiate and to observe structure changes in boundary regions.
Direction change of dislocations on passing a growth sector boundary in quartz crystals
Authors: Alter U. , Voigt G.
Published: January 2007

The behaviour of dislocations in quartz crystals changing their direction while passing from one growth sector into another where studied with X‐ray topography. The investigations were performed on crystals which had been grown in c direction from seeds cut from different growth sectors. The dislocations are newly arranged according to KLAPPER's theory, when they enter a growth sector with a different direction.
Irradiation‐induced change of valence of Cr3+ ions doped in alkali sulphates
Authors: Alybakov A. A. , Gubanova V. A. , Kudabaev K. , Sharsheev K.
Published: January 2007

It is shown by means of investigation of both optical absorption spectra and Roentgen K‐lines of chromium doped in LiKSO4, LiNaSO4, and Li2SO4 · H2O crystals, that X‐irradiation results in change of the impurity charge in a following way: Cr3+ + h → Cr4, Cr4+ + h → Cr5+.
Production of sapphire tubes for high‐pressure sodium lamps using the stepanov method at high rates of growth
Authors: Borodin V. A. , Steriopolo T. A. , Tatarchenko V. A. , Chernyshova L. I. , Yalovets T. N.
Published: January 2007

The process of the Stepanov growth of sapphire tubes is studied at the growth rates up to 20 mm · min−1 in a Mo crucible with graphite succeptor. It is established that the main factor preventing the production of high‐quality samples is contamination of the melt due to the gas transport reactions the growth chamber atmosphere and formation of oversaturated carbon solid solution in the Al2O3 matrix. The decomposition of this solid solution gives rise to the second‐phase‐particle precipitations. The production of highquality sapphire tubes at the growth rates up to 20 mm · min−1 is possible with a careful elimination of water vapours and oxygen from the growth chamber atmosphere.
Polymorphism and aging in terephthalic acid
Authors: Saska Michael , Myerson Allan S.
Published: January 2007

The role of the polymorphic transformation was investigated by X‐Ray diffraction in the habit modification process of terephthalic acid reported earlier (Gaines, Myerson). Contrary to the expectations it was found that only one of the two polymorphs described in the literature (Bailey, Brown) was present. Using an interatomic function derived (Derissen, Smit) to approximate the crystallographic properties of this class of organic acids, we calculated the lattice energies of the two proposed polymorphs of terephthalic acid. These were found to be 41.02 and 39.99 kcal/mole for the polymorphs I and II, respectively. The heat of transition calculated (1.03 kcal/mole) is small enough to be overcome by an increase of the enthropy term and the polymorphic transition is realizable.
Nucleation and precipitation in an Al‐Si(1 at.%) alloy investigated by positron annihilation
Authors: Krause R. , Dlubek G. , Brümmer O. , Skladnikiewitz S. , Daut H.
Published: January 2007

In AlSi alloys incoherent precipitates containing the pure solute element and having diamond cubic crystal structure are formed during a post‐quench annealing without formation of any metastable phase (Mondolfo). Quenched‐in vacancies have a strong effect on rates of precipitation from solid solution by transporting Si atoms as well as by their influence on the nucleation process. One suggestion is the precipitate formation by homogeneous nucleation of small Si clusters rich of vacancies (see for instance Beller). Another picture is the heterogeneous precipitation.

Positron annihilation can be expected to be very useful in studying small precipitate nuclei and the role of vacancies in the nucleation process. Positrons provide information of the concentration, configuration and internal structure of such lattice defects in solids, like dislocations, vacancies and vacancy‐clusters (Hautojärvi). The method is also very fruitful in studying small coherent precipitations (Dlubek et al. 1981). The aim of the present work is to study the nucleation and precipitation processes going on in an AlSi (1 at.%) alloy between room temperature and 300 °C by measuring the positron lifetime spectra.

The spectra of pure, well annealed metals without any localisation sites are one‐component exponential decay spectra. The time constant is called mean positron lifetime (in Al:τ = 165 ps). It is a measure of the reciprocal electron density. If positrons are localized at a certain kind of traps (such like vacancies or dislocations) a second exponential decay component will appear. The lifetime of the second, longer component is characteristic of the kind of the trap, the intensity of this component is connected with the trap density. It is for instance possible to distinguish clearly between monovacancies, divacancies and small vacancy clusters on the basis of the τ2 values (Hautojärvi).

The investigated AlSi(1 at.%) alloy was prepared from 4 N materials. After homogeneisation at 560 °C for some hours the samples were quenched into water at room temperature. Isochronal annealing treatment of samples was performed in 20 K steps (0.5 hours). After each annealing step the samples were slowly cooled down from the annealing temperature to room temperature within 5 minutes. Figure 1 shows the results of the isochronal annealing experiment.
Control over gas bubble distribution in shaped sapphire crystals
Authors: Borodin V. A. , Steriopolo T. A. , Tatarchenko V. A. , Yalovets T. N.
Published: January 2007

Bubble distribution in shaped sapphire crystals grown by Stepanov technique is found to depend on the field of velocities of the melt flows between the top surface of a die and the crystallization front. A die design defining the flows in the meniscus is a tool for control over the bubble distribution.
Composition and kinetic characteristics of vapour phase during mercuric iodide growing
Authors: Lyakh N. V.
Published: January 2007

The results of thermodynamical analysis of the vapour phase are presented for mostly often used growth conditions. It is shown that the vapour phase may contain: HgI2(g), Hg(g), I2(g), I(g). However, the degree of decomposition does not exceed one percent. Moverover, the following dependences are calculated and presented in a graphic form for HgI2 + I2 vapour mixture: the coefficient of dynamic viscosity from composition and temperature; the coefficient of diffusion with temperature and pressure; the coefficient of heat conductivity from composition and temperature.
Agglomeration of potash alum crystals
Authors: Karel Miloslav , Nývlt Jaroslav
Published: January 2007

Crystals of potash alum, crystallized in suspension at higher supersaturations, are partially agglomerated. Two sets of experiments have been chosen: batch experiments with precipitation of potash alum from its components and continuous crystallization by cooling. Using three different ways described in the preceding paper the size distribution of potash alum crystals was analyzed and the effect of agglomeration on calculated kinetic data demonstrated.
Nonstoichiometric defects in YAG and YAP
Authors: Kvapil Jiří , Kvapil Jos. , Perner B. , Mánek B. , Blažek K. , Hendrich Z.
Published: January 2007

Spectroscopic properties of undoped YAG and YAP grown under reducing protective atmosphere were compared. Blue (with F centre) or brown (with 0− centre) varieties both of the materials were prepared in the dependence of the Al2O3:Y2O3 ratio in the melt. Colour intensity depends on the H2O:H2 ratio in the protective atmosphere and on the sign of electrical potential above the melt level.

The coloration may be easily removed by an annealing at > 1200–1400 °C. All the irregularities of the colourations or their remowing by annealing may be attributed to the presence of impurities.
The migration of gas‐filled brine inclusions in rock salt under a temperature gradient
Authors: Müller E.
Published: January 2007

In natural halite crystals two sorts of inclusions will move if there exists a temperature gradient. The direction of moving brine inclusions is orientated towards the heat source.

Brine inclusions which additionally contain more than 10% gas move towards the cold end of a specimen. This model is well known but detailed information about the migration mechanism of these so‐called SORBY inclusions have been lacking in literature so far.

In this paper it will be demonstrated that SORBY inclusions having a diameter of up to 20 micrometers can move undisturbed through the crystal. SORBY inclusions with a diameter of more than 20 micrometers are fixed and form droplets with their tips directed towards the cold side of the specimen. Later when the tips have grown the inclusions will emit a new daughter inclusion which can move through the crystal. The velocity of migration depends on the generation of daughters.

Extended kinds of SORBY inclusions are stable for a long time. However, these can decay into many individuals which will move through the crystal like the others.
Reactor problems in modified chemical vapour deposition (i). the collapse of quartz glass tubes
Authors: Kirchhof J.
Published: January 2007

In the case of the so‐called “Modified Chemical Vapour Deposition” for the preparation of optical fiber preforms, the quartz glass reactor is identical with the substrate. Therefore, the knowledge of reactor properties such as the viscous flow of the tubes (collapse) and the heat transport through the wall are especially important for a successful control of the process. As a first step, an analysis is presented for the calculation of the viscous flow of the tubes under the real conditions of dynamic heating by a traversing flame. The experimental determination of the material parameters surface tension and viscosity by collapsing experiments yields an approach to the problem of the temperature distribution in the tube wall.
The coprecipitation of magnesium hydroxide aluminium hydroxide powders from aqueous solution with sodium hydroxide: Precipitate compositions and coprecipitation mechanisms
Authors: Packter A. , Panesar K. S.
Published: January 2007

Magnesium aluminium hydroxides were coprecipitated from different mixed metal cation solutions — at total CM = 0.1 M and Mg/Al2 ratios from 1 to 6 — with sodium hydroxide solution at ambient temperature, with different pre‐ageing conditions for the aluminium hydroxide pre‐precipitate. The coprecipitations were monitored by potentiometric (pH) titration and the final precipitate compositions were examined by chemical analysis, infrared spectrophotometry and thermal analysis.

Magnesium hydroxide was coprecipitated onto completely recrystallised aluminium hydroxide as a simple mixture.

Generally, with no to three days pre‐ageing, microcrystalline aluminium hydroxide was first precipitated at pH about 4; this then partially redissolved on further addition of sodium hydroxide (to form hydroxoaluminate anion) and magnesium aluminium hydroxide coprecipitates were formed continuously at pHs from 8.0–8.7 to 12.0–12.5. Their compositions were similar to the magnesium hydroxoaluminate hydrates formed by direct precipitation from high pH sodium hydroxoaluminate solutions.
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Interatomic force constants and localized effective charges in sphalerite‐structure compounds
Authors: Neumann H.
Published: January 2007

The Keating model with one bond‐stretching and one bond‐bending force constant and a localized effective charge to account for long‐range Coulomb forces and dipole‐dipole interactions is used to analyse the lattice vibrational properties of sphalerite‐structure binary compounds. It is shown that the trends in the model parameters can be readily explained in terms of the bond length and the bond ionicity.
The variable shaping technique — a new method of the sapphire growth
Authors: Borodin V. A. , Steriopolo T. A. , Tatarchenko V. A.
Published: January 2007

The paper presents results on sapphire growth by a new method which enables one to vary a configuration crystal cross‐section during the crystallization process. The field of application of those principally new products is also discussed.
A modified heater system for RF‐Czochralski equipments
Authors: Reiche P. , Hermoneit B. , Schultze D.
Published: January 2007

The temperature gradients in a Czochralski‐type crystal growth equipment with induction heating can be advantageously influenced by additionally heating the growing crystal and the crucible bottom during the pulling procedure. An experimental solution is presented for both afterheater and bottom heater coupled to the same induction coil as the crucible.
On the determination of kinetic data for the continuous crystallization of potassuim chloride
Authors: Kodura J. , Gramlich K. , Karwoth R.
Published: January 2007

A method for the determination of the kinetic constants and the realization of experiments for the bulk crystallization from solutions with particular reference to potassium chloride have been described. A new relation has been used for determining the kinetic constant, i, affording the advantage of being less sensitive to experimental errors. It can be regarded as fitting quite well with the data reported in the literature. A marked trend in the decrease in magnitude of the superscript, i, with increasing companion salt contents is noted. The value of i varies from 3.8 for technical potassium chloride to 2.0 for a fourcomponent solution.
Surface topographical studies of prism faces of ammonium tartrate single crystals
Authors: Saraf A. G. , Saraf K. B. , Wani P. A. , Bhandari S. U. , Bhoraskar S. V.
Published: January 2007

A study of surface structures of Prism faces (110) of ammonium tartrate single crystals grown by gel technique is described and illustrated. Vertical striations closly and widely spaced are observed. Isolated as well as densely populated rectangular elongated hillocks are reported and mechanism of the growth of these faces is assessed in the light of observed surface structure.