bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat capacity and thermodynamic properties of LiGaO2 from 180 to 700 K
Authors: Neumann H. , Kühn G. , Neels H. , Nowak E. , Pirl E.
Published: January 2007

The heat capacity at constant pressure of LiGaO2 is measured in the temperature range from 180 to 700 K. An analysis of the experimental data shows that the anharmonic contribution to the heat capacity can be described by a polynomial of fourth order in the temperature. The standard enthalpies and entropies relative to 298.15 K are calculated from the measured heat capacity. Estimates of the standard enthalpy and entropy at 298.15 K are given.
X‐ray diffraction effects from 2H crystals undergoing transformation to the 4H structure by the shear mechanism
Authors: Sebastian M. T.
Published: January 2007

The 2H or ABAB… structure may be transformed to the 4H or ABCB… structure if deformation faults occur in a non‐random manner. The theory of X‐ray diffraction from one‐dimensionally disordered crystals undergoing the 2H → 4H structural transformation by the deformation mechanism is developed. For this it is necessary to consider that the faults are not distributed entirely at random but tend to occur in such a manner as to statistically create a 4H structure. The X‐ray diffraction effects are predicted.
Simplified treatment of transient doping behaviour in CVD (II)
Authors: Arnold H.
Published: January 2007

Using circuit representations, the influence of the deposition rate for semiconducting CVD layers on transient behavior of doping concentrations is rechecked for a simple decomposition reaction of the dopant species. The existence of a space‐charge region below the surface is taken into account. Simple estimations show that atomically abrupt doping transitions are to be expected, if the storage of foreign atoms in the surface is responsible for transient behaviour, and if their concentration becomes frozen in. In order to explain flatter doping profiles occurring with As and P in Si, molecular storage has to be included in the study. Only some simplified cases with one capacitance, or a sum of capacitances, in the circuit representation are being treated.
Growth and removing of tungsten whiskers under controlled conditions
Authors: Aleksandrov L. N. , Mordyuk V. S. , Tokarev A. T. , Rubtsov A. A.
Published: January 2007

The growth kinetic and size decreasing process of tungsten rod‐like crystals by heating in the iodine vapour are studied. Effects of tungsten filament temperature (2400 – 3500 K), iodine concentration (to 6 mg/cm3) and water contents (0.01 – 0.05 mg/cm3) are shown. Maximal growth rate of tungsten whiskers to 30 μm/min. Stopping of the growth and following removing by iodine reactions take place after heating to 3500 K.
Pyroelectric, dielectric, piezoelectric and electrooptic properties of monoclinic nitrilotriacetic acid N(CH2COOH)3 and orthorhombic X2Zr[N(CH2COO)3]2 · 2 H2O (X = K, Rb, Cs)
Authors: Richter U. , Haussühl S.
Published: January 2007

Large single crystals of monoclinic nitrilotriacetic acid, N(CH2COOH)3, NTA, and of orthorhombic isotypic X2Zr[N(CH2COO)3]2 · 2 H2O (X = K, Rb, Cs) have been grown from aqueous solutions. They possess optical quality and have dimensions up to 10 mm and larger. The complete dielectric, piezoelectric and electrooptic tensors have been determined. The maximum longitudinal and transversal piezoelectric effects exceed those of α‐quartz by roughly a factor 11. The pyroelectric effects in NTA and in the X2Zr‐salts (X = K, Rb, Cs) are by about a factor 3 larger than that in tourmaline, whereas the maximum electrooptic effects amount only to about half of that in KH2PO4. Qualitative measurements of the nonlinear optical properties by the aid of a SHG powder test and on single crystals revealed effects comparable with those observed in LiIO3. Phase matching is possible in these compounds. Replacing X by NH4 or Tl also acentric crystals are obtained with strong polar properties.
Phase transition of nematic to smectic C through an intermediate boundary induced smectic A structure
Authors: Simova P. , Petrov M.
Published: January 2007

An intermediate phase has been observed at the transition nematic to smectic C where a smectic A structure induced by the boundaries and a nematic phase exist simultaneously. The temperature interval of existence of the intermediate phase is of the order of one tenth of degree. Several conditions are necessary for its appearance: the latent heat L of the phase transition nematic‐smectic C of the liquid crystal should be sufficiently small (L < kBTc); the nematic phase should undergo a bend deformation by the boundaries (possibly a twist one as well) and the transition nematic‐smectic C should be carried out as slower as possible.
Growth of KDP single crystals by temperature reduction under diffusion transport
Authors: Santos A. , Garcia‐Ruiz J. M.
Published: January 2007

Growth rates of 37 μm/hour for {010} faces and 40 μm/hour for [001] directions have been found for KDP crystals growing in gelled media by temperature reduction. These values, higher than those recorded in alcohol‐diffusing techniques are in the range of more classical methods. A device for obtaining larger crystal size is also described.
On the bindings in the elements between V and Ga. 2. Phases from Co to Ga
Authors: Schubert K.
Published: January 2007

The analysis of bindings in the elements V to Fe (Part I) may be continued for the elements Co to Ga, so that further independent experimental data find a unified interpretation. The following explanations may be mentioned: (1) the occurrence of the Mg type at n = 9, (2) the valence electron concentration N = 0.6 at n = 8, 9, 10, (3) the tetragonal structures at n = 11, (4) the anomalous dependence of the structural axial ratio on n near n = 11, (5) the anomalous crystal axial ratio at n = 12, etc. A useful analysis parameter is the site number ratio N going through a maximum at n = 8, 9, 10 and causing thus the close chemical relationship of Fe, Co, Ni. One of the physical conditions for the phenomena is the high compliance of the correlation in the d‐band (e correlation) permitting predominantly a full occupation ceasing only at n = 13. The diversity of interpreted phenomena not understood earlier provides a corroborating support to the hypotheses of the plural correlations model.
The current understanding of epitaxial CVD silicon doping in the light of modelling and theory development (II). Theoretical foundations and incorporation equations
Authors: Kühne H.
Published: January 2007

Theoretical foundations selected from related fields of science (thermodynamic and chemical equilibria, kinetics of surface‐catalized reactions, open systems and steady‐state equilibria, solid‐state physics of semiconductors) are applied to epitaxial silicon layer doping to reveal the doping process mechanism. In this way it is shown how the empirically based relationships between the controlling parameters of the process and the doping effect (c.f. part I) can be explained by theory. In the course followed, the historical evolution is neglected in favour of the logical interconnection between the empirical and theoretical foundations.
Crystal growth and domain structure of triglycine sulphate doped with Pt(II)
Authors: Březina B. , Havránková M.
Published: January 2007

The single crystals of triglycine sulphate doped with bivalent Pt‐ions (TGS‐Pt) were grown in full‐shaped form, i.e. with many growth sectors. The domain structure of individual growth sectors was studied by the liquid crystal method. The growth sectors are mostly in a single domain state but spontaneous polarization is reversed in growth sector boundaries, which coincide with charged domain walls. Only the growth sector 001 reveals a blockshaped domain structure, however it differs from usual lenticular domains of the undoped TGS. The concentration of Pt in various growth sectors is different. The growth sectors with the higher concentration of Pt than 3 × 10−2% exhibit the unipolarity stable against thermal schocks.
Microstructures of gel‐grown ammonium hydrogen tartrate single crystals
Authors: Desai C. C. , Hanchinal A. N.
Published: January 2007

Single crystals of ammonium hydrogen tartrate (AHT) have been grown in silica gels by employing the controlled reaction between ammonium chloride and tartaric acid. Transparent AHT crystals upto 24 × 4 × 3 mm3 in size have been grown at room temperature. Optical and electron‐optical studies have been made on the various surface structures of {010} faces of the grown crystals. A variety of growth striations and growth hillocks have been observed. Growth layers modified by the presence of misaligned microcrystals have been illustrated. It has been suggested that two‐dimensional nucleation, spreading and pilling up of growth layers is mainly responsible for the growth of these crystals and the implications are discussed.
Electrical conduction in ferroelectric lead hydrogen phosphate single crystals
Authors: Desai C. C. , Ramana M. S. V.
Published: January 2007

Single crystals of LHP (Lead Hydrogen Phosphate) have been grown using the controlled reaction between lead nitrate and orthophosphoric acid solution by diffusion process in silica gel medium. Transparent crystals upto 6 × 4 × 3 mm3 in size have been grown at room temperature. The d.c. electrical conductivity of both single crystals and pelletized samples of LHP have been studied in the temperature range from 313 to 968 K. It has been observed that: (i) the d.c. conductivity of the crystalline sample is greater than that of thepellet sample, (ii) three distinct electrical conductivity processes have been observed and are interpreted as extrinsic, intrinsic, phase changes, and (iii) the activation energy for the conduction in the crystalline sample is greater than that of the pellet sample. The magnetic susceptibility measurements reveal that the paramagnetic characteristic of these materials and the implications are discussed.
Dielectric studies on binary mixtures containing 4‐trans‐4′ ‐n‐hexyl‐cyclohexyl‐isothiocyanato‐benzene
Authors: Raszewski Z. , Dąbrowski R. , Stolarzowa Z. , Zmija J.
Published: January 2007

We have studied binary mixtures with an induced smectic phase of 4‐trans‐4′ ‐n‐hexylcycohexyl isothiocyanatobenzene (6CHBT) with 4‐n‐ethyl‐4′‐pentylazoxybenzene (EPAB) by means of dielectric, microscopic and refractometric measurements. The effective values of components p ⟂ and p∥ of the dipole moment per one molecule of the mixture have been calculated from values of ϵ ⟂ and ϵ ∥. As a result of our studies, we have established that the heterocomplexes formed in the mixture are so weak that they do not cause any essential changes in the distribution of molecule charges. The observed deviations from additivity of the dielectric constant of the mixture are caused solely by a non‐additive behavior of the mixture density.
X‐ray quantitative determination of the phases in a batch for the synthesis of poly‐ and monocrystal yttriumaluminium garnet
Authors: Petrov Sr. , Chomakov Iv. , Bogdanov B. I.
Published: January 2007

For the synthesis of ceramics and single crystals of yttriumaluminium garnet, a batch consisting of Y2O3 and Al2O3 is first treated thermally in order to obtain the garnet phase Y3Al5O12. It is possible to make a choice of the optimum technological parameters of the batch if the amounts of all oxide phases, present during the synthesis, are well known.

A combined X‐ray quantitative method is suggested for this purpose. The initial oxides and a garnet phase are determined by the method with external standard. The rest two impurity oxide phases are determined as binary system. The specific diffraction characteristics of the present compounds were taken into account. The amounts of all phases in the batch, treated thermally from 1373 to 2075 K at every 100 K are shown.
Optical, X‐ray, and calorimetric studies of phase transitions in ND4BeF3
Authors: Waśkowska A. , Pietraszko A. , Czapla Z.
Published: January 2007

Phase transitions in ND4BeF3 crystals at T1 = 330 and T2 = 245 K were studied by specific heat (DSC) and X‐ray lattice parameters measurements in function of temperature. These ferroelastic transitions are accompanied by anomalous heat absorption, sudden changes in the unit cell parameters and crystal symmetry. Formation of domain structure in particular phases examined under a polarizing microscope is also described. Domain walls of the type (100), (010), and (001) observable at room temperature indicate on the triclinic symmetry of the Phase II. Above T1 the crystal becomes orthorhombic. First‐order phase transition at T2 causes the symmetry of the crystal in the Phase III to be monoclinic with the c‐axis unique. The phase transition diagram is proposed and compared with the phase situation in nondeuterated NH4BeF3 crystals.
Electrical conductivity of some mixed ferrites at Curie Point
Authors: Reddy P. Venugopal , Pratap K. J. , Rao T. Seshagiri
Published: January 2007

The behaviour of electrical conductivity of four ferrite semiconductor systems viz., Li‐Ni, Mn‐Mg, Co‐Zn and Ni‐Zn having different compositions has been studied in the vicinity of magnetic transformation temperature. Contrary to the predictions of an empirical formula (PARKER's) all the ferrites under investigation have exhibited marked and clear transitions at the Curie Point.
The precipitation of aluminium hydroxocarbonates powders from aqueous solution: Precipitate compositions and precipitation mechanisms
Authors: Packter A. , Panesar K. S.
Published: January 2007

A series of aluminium hydroxocarbonate hydrates were prepared by precipitation from aluminium nitrate solution, with five sodium hydrogen carbonate‐sodium carbonate solutions of different pH, at ambient temperature. The course of precipitation was monitored by pH measurement and the final precipitate compositions were determined by chemical analysis, infra‐red spectrophotometry, X‐ray diffraction and thermal analysis.

Precipitation generally occurred through three stages, primary precipitation of materials with low carbonate content at low pH with evolution of carbon dioxide, their dissolution to form hydroxcarbonato anions and then secondary reprecipitation of the final products at higher pH. These materials were mixtures of polyhydroxoaluminium carbonate hydrates of general composition Aln(OH)3n‐2CO3 · hH2O (where n = 2, 4, 6 and h = 6–8); their CO3 content increased with increasing pH and carbonate anion content of the precipitant solution.
The effect of manganese additions on the structure changes proceeding in rapidly solidified Al‐Cu alloys
Authors: Dzuong Lecong , Löffler H. , Thang Nguyen Quyet , Tri Hoang Minh
Published: January 2007

The effect of Mn additions (0… 2 wt%) on the decomposition of rapidly solidified Al‐4.0 wt% Cu alloys (cooling rate 103 to 104 K/s; LQ treatment) were studied during ageing between RT and 450 °C by hardness, X‐ray methods and electron microscopy. The results were compared with alloys homogenized in the region of the solid solution (SQ treatment).

(i) The LQ treatment results in a quite better homogeneous distribution of the alloyed elements than the SQ one, that is less particles of intermetallic phases are present in the ascast state. (ii) At T < 250 °C Mn additions affect the decomposition kinetics by trapping of vacancies (retardation) and the diminution of the solubility of Cu atoms (acceleration). The first effect dominates in the stage of G.P. zone formation, the second one during precipitation of intermediate phases. (iii) At T ≧ 300 °C the intermetallic compound Cu2Mn3Al20 forms associated with a significant increase of the hardness.
An X‐ray diffraction refinement of the crystal structure of natural apophyllite
Authors: Pechar F.
Published: January 2007

The crystal structure of apophyllite (Andersberg — GDR), with a = 8.966(2), c = = 15.767(1) Å, P4/mnc, z = 2, Q = 2.35 gm · cm−3, has been refined (R = 0.035) by least squares with 976 reflections collected with a diffractometer. Apophyllite is a sheet structure with the bringing SiO bond lengths 1.6236 Å, while the non‐bridging bond length SiO(3) is 1.5843 Å. The two independent SiOSi angles are 140.09, 140.76 degrees. The mean SiO bond length is 1.6138 Å.

As it was not possible to locate unequivocally the H‐atoms with the X‐ray data, the interpretation of the of water in the structure was based on the charge balance approach of DONNAY and ALLMAN. Assuming that the fluorine ion is bonded to calcium ion (Ca‐F = = 2.416 Å) and to H3 atom (F‐H3 = 0.9145(1) Å) and water molecule hydrogen bonded to silicate framework. The average bond distances O‐H are 0.962(2) Å and angle 105.24(1)°.
X‐ray investigation of the mechanisms of phase transformations in single crystals of ZnS, ZnxCd1−xS, and ZnxMn1−xS (II). Comparison of observed and calculated diffraction effects
Authors: Sebastian M. T. , Krishna P.
Published: January 2007

The experimentally observed intensity profiles recorded from ZnS, ZnxCd1−xS and ZnxMn1−xS crystals at different stages of the 2H‐3C and 2H‐6H transformations are compared with those computed theoretically from the three parameter model in the previous paper. It is found that the 2H‐3C and 2H‐6H transformations occur by the nonrandom nucleation of deformation faults. The probability of the growth of a nucleus is much greater than that of the creation of a fresh nucleus. At least two different fault probabilities have therefore to be employed in computing the diffraction effects in each case. The transformation behaviour of ZnxCd1−xS and ZnxMn1−xS crystals is strongly influenced by variations in stoichiometry (x). Large values of x (x > 0.95) favour the 2H‐3C transformation, whereas smaller values (x ≦ 0.94) favour the formation of the 6H phase. A comparison of the calculated and observed intensity distributions indicates that in some crystals the 2H‐3C and 2H‐6H transformations occur simultaneously in different regions of the same single crystal.
Crystal and molecular structure of Bis(glyoxal‐bis‐tert.butylimine)nickel(0)
Authors: Görls H. , Walther D. , Sieler J.
Published: January 2007

The crystal structure determination of the title compound was undertaken to determine the coordination geometry of nickel atom. Bis(glyoxal‐bis‐tert.butylimine)nickel(0) (C20H40NiN4) crystallizes in the space group Pna21 with Z = 4, a = 18.546(6), b = 9.331(8), and c = 13.505(8) Å. The structure was solved by the heavy atom method and refined to R = 0.065. The molecule has four‐coordinate nickel atom. The coordination geometry about the nickel atom is tetragonal.
X‐ray determination of thermal expansion of Na(ClO3)x(BrO3)1−x mixed crystals
Authors: Subhadra K. G. , Hussain K. A.
Published: January 2007

Lattice constants of sodium chlorate and sodium bromate and their mixed crystals were determined over the temperature range from room temperature to 320 °C. The observed lattice constants for the various compositions show strong deviations from those expected from Vegard's rule. The lattice constants at various temperatures were fitted to polynomials of type a = a0 + a1t + a2t2. The linear coefficients of expansion for the Na(ClO3)x · (BrO3)1−x series varies non‐linearly with composition showing negative deviations from linearity.
Infrared optical properties of Cu1−xLixSe2 thin films
Authors: Sobotta H. , Neumann H. , Mitaray S. , Riede V. , Kühn G.
Published: January 2007

Infrared absorption spectra of Cu1−xLixInSe2 thin films are measured at room temperature in the wavenumber range from 100 to 600 cm−1. The spectra exhibit two absorption bands in the wavenumber ranges 200–210 cm−1 and 330–355 cm−1 which are ascribed to vibrational modes due to InSe and LiSe vibrations, respectively. The influence of the phase transition from the chalcopyrite structure to the β‐NaFeO2 structure in the composition range x = 0.5–0.6 on the vibrational characteristics is established and discussed.
Hyperfine structure of Cr5+ EPR spectra in X‐irradiated potassium halide crystals doped with CrO and Ca2+
Authors: Akchalov Sh. , Alybakov A. , Zhanibekov M. , Karashev T. K. , Tojchiev N.
Published: January 2007

The hyperfine structure has been investigated in the EPR spectra of X‐irradiated KCl: CrO, Ca2+ and KBr: CrO, Ca2+ crystals. Preliminarily spectra were simplified by means of heating the crystals up to 400 K for KCl and 440 K for KBr, that destroys the less stable CrO · V centers. It is ascertained, that principal directions of g‐ and A‐tensors do not coincide, and principal A‐values are determined. Calculations, making use of the experimental meanings of g‐ and A‐tensor components, showed, that the degree of distortion of oxygen tetrahedra in CrO · Ca2+ · V centers is almost the same in both KCl and KBr crystals; besides, these calculations suggest the existence of a strong covalent bonding between the central Cr5+ ion and four oxygen ligands in CrO ions.
Method of X‐ray spectral microanalysis of PbTe and SnTe obtained by the iodide method
Authors: Assenov R. , Moshnikov V. A. , Patarov B. , Yaskov D. A.
Published: January 2007

This an examination of the characteristics of the X‐ray spectral microanalysis of the tellurides of lead and thin, obtained by the iodide method. It was demonstrated that applying the method of calculating the composition in relation to the relative intensity of the characteristic X‐ray radiations of the analytical lines TeLα and ILα secures the possibility of analyzing relief surfaces. Besides that, the method makes it possible to make calculations without using numerous traditional semi‐empirical expressions under conditions of changes in the values of the accelerating voltage.
A simple optical method of measuring the tilt bias angle of liquid crystals
Authors: Jain S. C. , Singh H. K. , Balakrishnan K. S. , Chandra S.
Published: January 2007

A simple optical method based on refractive indices measurement for determining the tilt bias angle of liquid crystals is described. The required refractive indices no, ne and nθ are measured by (i) Abbe's refractometer and by (ii) optical wedge method. The tilt bias angle by this technique can be determined to accuracy of ± 0.2° in the high tilt angle range (20° to 40°). This method is rather simple and quick and does not require any external magnetic field and/or knowledge of other physical constant of liquid crystals, as are necessary in some of the earlier reported methods.
Induced SA phases in binary systems with EDA complexing
Authors: Pelzl G. , Böttger U. , Diele S. , Demus D.
Published: January 2007

The phase diagrams of 13 binary systems are presented in which electron donor‐acceptor (EDA) complexing is clearly detectable. In all binary systems studied the same electron donor compound was used whereas the electron acceptor compounds were members of two homologous series. It was found that the induction of smectic A phases increases with increasing length of the alkyl chain of the acceptor compound and with increasing stability of the complexes.
New high precision lifetime measurements in pure copper and a 0.3 at.% AgSb alloy with a BaF2 lifetime spectrometer
Authors: Ederhof M. , Lühr‐Tanck W. , Sager A. , Kurschat Th. , Hehenkamp Th.
Published: January 2007

The temperature dependence of positron annihilation in copper and a 0.3 at.% AgSb alloy has been investigated by measuring the positron lifetime. In both cases the vacancy lifetime is nearly independent on temperature while the bulk lifetime shows a rapid increase after the onset of detectable vacancies. This increase can be explained by trapping during thermalization with an enhanced trapping rate.
Structural phase transitions in Cu2–xFeyS crystals
Authors: Ismailov D. I. , Asadov Yu. G. , Gasymov G. B.
Published: January 2007

Crystals with Cu2−xFeyS compositions (x = 0.30, 0.25, 0.20, 0.15; y = 0.05) have been synthetized and obtained by the method of slow cooling. X‐ray diffractometric studies have shown that at room temperature the above crystals consist of an orthorhombic phase (anilite), a monoclinic phase (djurlite), and their metastable high‐temperature facecentered cubic phases (FCC)1 and (FCC)2, respectively. A crystallographic relation has been found between the lattices of the orthorhombic, monoclinic and (FCC)1 phase. It is shown that all these phases transform in the final analysis to a single high‐temperature fcc phase. All the transitions are reversible, i.e. in the course of inverse cooling to room temperature, the diffraction patterns are restored completely in reverse order.
Positron lifetime in inhomogeneous metallic materials
Authors: Gondzik J. , Stachowiak H.
Published: January 2007

A positron is considered in an inhomogeneous jellium model according to a formalism following from the theory of liquids. This leads to a nonlocal treatment of the screening of this particle. Annihilation rates have been found inferior to the ones for a homogeneous electron gas, in agreement with positron lifetime measurements.
The interaction of Ni and Au with HCl during quenching
Authors: Beasley P. , Alam A. , West R. N.
Published: January 2007

During annealing of Ni and Au, previously quenched into HCl at 203 K, annealing stages that cannot easily be explained in terns of the migration of open volume defects are observed. The contamination of the hot samples with hydrogen released from the quenching fluid is suggested as the origin of these additional annealing stages.
Study of clustering of vacancies in cold‐worked nickel by positron annihilation spectroscopy
Authors: Sundar C. S. , Bharathi A. , Gopinathan K. P.
Published: January 2007

The clustering of vacancies occurring during the isochronal and isothermal annealing treatments of a 40% cold‐worked nickel has been investigated through positron lifetime measurements. The observed variation in lifetime has been quantitatively understood by modelling the defect reactions amongst vacancies leading to the formation of vacancy clusters.
Studies on the relation between the magnetic properties and positron lifetime of ALNICO 8 permanent magnet alloys
Authors: Shan‐Yi Liu , Guan‐Qu Zhu , Shao‐Jie Wang
Published: January 2007

Alloys ALNICO 8 have been wildly used in industries for their excellent magnetic properties and reliable temperature stability.

The present paper has studies the relation between the maximum magnetic energy product (MMEP) of columnar crystallizated AlNiCo 8 permanent magnet alloys cooled continuously in magnetic fields and positron lifetime in this material. The experimental results show that the minimum decay constant τ1 reaches gradually its saturation as MMEP increase, this means the trapped effect obviously happens in the specimens with low MMEP. With the increase of MMEP, the τ2 component reflecting the crystal imperfection decreased, hence, the crystal perfection improved. Mössbauer spectroscopic results also show that with the increase of MMEP, the more parts of magnetic moments orientate to magnetizate direction. This work gives valuable data to improve the properties of materials.
Application of the positron annihilation method for investigations of the diffusion of helium in metals
Authors: Pajak J. , Pietrzak R. , Szatanik R. , Rozenfeld B.
Published: January 2007

A method which permits to determine the diffusion coefficient of helium in metals from the measurements of the time dependence of the intensity of annihilation radiation has been outlined. The diffusion of helium cold‐rolled and cold‐rolled and annealed nickel has been investigated. It has been found that the value of the diffusion coefficient of helium along the grain boundaries and dislocations in nickel is of the order of 10−13 cm2 s−1.
On the possibility of polytypism in semistatistically defected wurtzite‐type crystals of CdS
Authors: Horodecki A. J.
Published: January 2007

The analysis of extraordinary reflections of X‐ray pattern of CdS thin films is presented which indicates the existence of 22 H polytype. For the conditions that are favourable for polytypism a new dependence of Madelung constant on the crystal structure is proposed. All of the results are consistent with the concept of semistatistically defected wurtzite crystal.
The possible influence of electric moments on the growth of thin films of pyroelectrics from vapour phase
Authors: Horodecki A. J.
Published: January 2007

Electric moments of substrate surface interact with any polar species coming‐in from vapour phase. The re‐mapping of substrate electricity will be continued if both these species and crystals are of uniaxial polarity. Consequently, the additional field at the growing surface is the resultant of crystal “memory” and of pyroelectric charge and seems to be the main reason for the texture. Moreover, considering the microrelaxation of growth the numerous pairs of cation vacancy — anion vacancy are expected. The results indicate the way for understanding the peculiarities of X‐ray pattern of CdS thin films.
Epitaxy of AIBIIIC semiconductors
Authors: Schumann B. , Tempel A. , Kühn G.
Published: January 2007

Epitaxial layers of AIBIIIC compounds were grown by the flash evaporation technique and investigated using reflection electron diffraction. Geometric‐structural considerations allow the prediction of epitaxial relationships and types of epitaxy (one‐ or three‐dimensional, multiple orientation). These properties of the epitaxial layers were confirmed experimentally. Furthermore, the epitaxial temperature ranges, non‐equilibrium phases, defects, and special features of the epitaxial growth are described. Especially, the influence of lattice misfit is discussed.
Heat capacity of Ag6Ge10p12 from 180 to 550 K
Authors: Nowak E. , Neumann H. , Omar M. S.
Published: January 2007

The molar heat capacity at constant pressure of Ag6Ge10P12 is measured in the temperature range from 180 to 550 K and the standard molar enthalpies and entropies relative to 298.15 K are calculated on the basis of these data. From a comparison of the temperature variation of the apparent Debye temperatures in CuGe2P3 and Ag6Ge10P12 it is concluded that lattice anharmonicity is more pronounced in Ag6Ge10P12 than in CuGe2P3.
Chemical etching and polishing of InP
Authors: Kurth E. , Reif A. , Gottschalch V. , Finster J. , Butter E.
Published: January 2007

This paper describes possibilities of several chemical preparations for the selective cleaning of InP surfaces. The investigations of the surface states after the chemical treatment were carried out by means of XPS measurements. A pre‐etching with (NH4)2S2O8:H2SO4:H2O and a polishing with 1% bromine in methanol produce optically smooth (100)‐ and (111) P surfaces free of oxides.
An estimation of fracture stress in a brittle solid
Authors: Majumdar B. , Dubey B. N. , Chandra B. P.
Published: January 2007

The present paper reports for the first time an exact analytic expression that can be used for obtaining fracture stress σF, when fracture occurs in the elastic limit and also when fracture occurs after general yield (σF > σY) in a brittle solid. The present paper may provide a new basis to fracture‐safe design of brittle materials.
Thermally stimulated depolarization currents in OH−‐doped NaCl and KCl crystals
Authors: Suszyńska M. , Capelletti R.
Published: January 2007

The main features of the high‐temperature ITC band are analyzed on the basis of experimental results obtained for NaCl and KCl crystals containing the hydroxyl ions. The unusual behaviour of this band has been compared with that described previously for alkali halides, AH, (LiF, NaCl, KCl) doped with some divalent cations, Me++, (Be, Eu, Ni, Pb).

It has been shown that — similar to the case of the Me++‐doping‐most of the results obtained can be explained in frames of the Maxwell‐Wagner‐Sillars model of interfacial polarization induced by the impurities forming the charge clouds to the dislocation lines. An ITC band can be detected due to the fact that these regions exhibit electric conductivity and dielectric constants different from those characteristic of the bulk material. The role of the charge of dislocations in the induced polarization phenomenon is shortly discussed.
Low temperature investigations of e−‐irradiated GaAs
Authors: Mascher P. , Kerr D. , Dannefaer S.
Published: January 2007

Positron lifetime measurements have been performed on electron irradiated chromium doped semi‐insulating GaAs as a function of annealing between 139 and 908 K. Trapping at negatively charged GaAs defects and by a vacancy mixture dominated by trivacancies took place in the as‐irradiated state. Upon annealing around 210 K divacancies were formed from the trivacancies as caused by migrating arsenic interstitials. Complete trapping prevailed up to 530 K but decreased then rapidly at higher temperatures due to the migration of divacancies which also remove the GaAs defects.
Dependence of positron capture rate on dislocation density in solid solutions of KCl—KBr
Authors: Dhanalakshmi S. R. , Nagarajan T. , Ramasamy S.
Published: January 2007

Generally well‐annealed alkali halide crystals exhibit three lifetime components. τ1 arises due to annihilation with anion and τ2 due to Bloch Ps. The origin of τ3 is not well understood. Positron lifetime and etching techniques have been performed on solid solutions of KCl100−xBrx with mole % of x = 0.0, 15, 30, 37, 50, 70, and 100. The positron lifetime spectra have been analysed to resolve into three components. The positron capture rate K3 for the longest lived component and the dislocation density shows a non‐linear variation with composition. The positron capture rate varies linearly with the dislocation density of the samples. The origin of τ3 is identified as due to positronium formation in the dislocations present in the samples. The trapping probability per dislocation has been estimated to be 2.2 × 10−12/s.
Positron lifetime studies of X‐irradiated N‐acetyl‐D,L‐alanine
Authors: Walker William W.
Published: January 2007

Polycrystalline samples of N‐acetyl‐D,L‐alanine (AA) which had received an X‐ray dose of approximately 6 Mrad have been studied by the positron annihilation technique. Data were obtained as a function of time following the radiation treatment, and also as a function of subsequent annealing temperature. The large decrease of the intensity of the longest lifetime component (I3) was observed to be reversible when assisted by heat treatment.
Structural characterization of the ammonium trimolybdate hydrate (NH4)2Mo3O10 · H2O
Authors: Hodorowicz S. A. , Lasocha W.
Published: January 2007

When normal molybdate solutions are acidified, various isopolymolybdates of increasing degrees of condensation are formed according to different acidifications and other conditions (Sasaki, Sillen; Tsigdinos; Tytko, Glemser). Attempts to identify some complexes have not, however, led to definite conclusions about their existence. In particular, Lindquist — basing on an analytical and X‐ray powder study — suggested that ammonium trimolybdates (NH4)2O · 3 MoO3 · aq described by some authors (Mellor; Guiter; Chans et al.) may be double salts of hepta‐ and octamolybdate. Recently, fibrillar crystals of ammonium isopolymolybdate have been isolated (Lasocha, Hodorowicz). The results of physicochemical analyses correspond to the formula (NH4)2Mo3O10 · H2O. In this paper we focus our attention on the structural characterization of the compound obtained.
Growth mechanism in atomic layer epitaxy (III) reevaporation of Cd and Te from CdTe (111) surfaces and thick elemental deposits monitored by quadrupole‐mass spectrometry
Authors: Herman M. A. , Juza P. , Faschinger W. , Sitter H.
Published: January 2007

Quadrupole‐mass spectroscopical (QMS) studies on isothermal reevaporation of Cd and Te species from the CdTe (111) surface have been performed in two extreme cases. The first concerns the reevaporation of thick, bulk‐like non‐crystalline Cd and Te films deposited in high vacuum at room temperature on the (111) surface, whereas in the second case evaporation of the constituent species from the bare single crystalline (111) surface has been investigated. The fluxes of the species desorbing in high vacuum (10−6 Pa) have been monitored with QMS and the desorption temperatures have been measured with a thermocouple mounted as near as possible to the sample surface. The following values Ea(Cd)bulk = 1.13 ± 0.12 eV, Ea(Te)bulk = 1.64 ± 0.18 eV and Ea(Cd)(111) = 1.13 ± 0.06 eV, Ea(Te)(111) = 1.92 ± 0.13 eV of the activation energies for these two cases have been determined from the slopes of the Arrhenius plots.

Using these experimental values, the numbers of atomic bonds NCd and NTe occurring in the atomic aggregates of quasi‐gas molecules forming the near surface quasi‐gas transition layers have been estimated. For Cd quasi‐gas molecules 2 ≤ NCd ≤ 5, whereas for Te molecules 3 ≤ NTe ≤ 10. However, no prediction concerning the number of atoms creating the quasi‐gas molecules could be made on the basis of the QMS investigations.

It has also been shown that Cd atoms evaporate from the bare single crystalline CdTe (111) surface with an activation energy that is equal (in the limits of the experimental error) to the activation energy for sublimation of Cd atoms from pure, non‐crystalline, bulk Cd pieces. The analogous activation energy measured for Te atoms is about 20% larger than that of the relevant sublimation process. This result confirms the fact that Te atoms are bound much stronger in the CdTe crystal lattice than Cd atoms.
Macrostructure of pyrolytic boron nitride
Authors: Arefiev K. P. , Lopatin V. V. , Surov Yu. P.
Published: January 2007

[Russian Text Ignore]
Spectrometer for the study of three‐photon annihilation of three‐photon annihilation of positrons
Authors: Georgiev A. , Misheva M. , Mishev P. , Toumbev G. , Vinarov N.
Published: January 2007

A three channel spectrometer for studying three‐photon annihilation is reported. It is based on a fast‐fast coincidence circuit and includes NaJ(Tl) scintillation detectors, constant fraction differential discriminators, a fast coincidence circuit with variable resolving time (6 ns—60 ns), a linear gate and a multichannel analyzer.

The possibility of using positron source 64Cu in the spectrometer, its advantages and disadvantages are discussed. In this connection we describe the special units coupled to the spectrometer as well as a method which helps to avoid the influence of the short decay time of 64Cu of the accuracy of the experimental results.
Automatic system for the storage and search of annihilation data
Authors: Abdurasulev Z. , Zhuravleva G. , Malyan V.
Published: January 2007

An automatic information‐searching system AIPS‐Positronika has been developed and is successfully working for several years at the Institute of Electronics of the Uzbek Academy of Sciences. It is intended for collecting, storing, searching and output of information on positron annihilation (Abdurasulev et al.). At present this system has been further developed as an annihilation data bank including the array of experimental annihilation spectra and their individual descriptions (Arifov et al.; Malyan et al.).
On the mechanism of AlSi alloy structure modification by metal antimony
Authors: Yaneva S. , Stojanova L. , Stoichev N. , Kamenova Z.
Published: January 2007

In the process of AlSi alloys solidification in presence of Sb the intermetallic compound AlSb is taking obviously a significant part. An adsorptional incorporation mechanism of AlSb action is proposed. It depends strongly on the antimony concentration in the melt.

The modifying effect is influenced also by a possibility of nucleation and growth of the AlSb phase itself.
Results of texture simulation in b.c.c. materials
Authors: Dörfel I.
Published: January 2007

Rolling textures of b.c.c. polycrystals are simulated by the „full constraint”︁ (FC)‐ and the „relaxed constraint”︁ (RC)‐Taylor model, by the FC‐model with glide asymmetry in {112}〈111〉slip systems included, by a combination of FC‐ and RC‐model, and by this combination with glide asymmetry included, respectively. Several cases of activated slip system families have been investigated. Simulation results are compared qualitatively with experimental ones.
Bulk modulus — volume relationship in alkali halides with rocksalt structure
Authors: Neumann H.
Published: January 2007

It is shown that the bulk modulus of the alkali halides with rocksalt structure follows the simple relation B = b0(1 — b1fc) V where V0 is the unit cell volume, fc the spectroscopically defined covalency of the chemical bond, and b0, b1, and n are constants having the same values for all compounds. This result is compared with the bulk modulus scaling law found for the tetrahedral semiconductors.
Photoelectrochemical solar cells based on TiS2/TiO2(TiOxSy) photoelectrodes
Authors: Chandra Babu K. S. , Srivastava O. N.
Published: January 2007

A new photoelectrode of TiS2/TiO2 alloy with a possible new TiOxSy phase has been synthesized for the first time in the present investigation. This photoanode exhibits improved photoelectrochemical (PEC) response as compared to either TiS2 or TiO2 photoelectrode. With this new photoelectrode high PEC conversion efficiency is evidenced by large photovoltage (840 mv) and significantly high photocurrent density (40 mA/cm2). The photovoltage obtained in the present system is significantly high and the photocurrent density is the highest reported so far for the TiO2 based systems. It has been suggested that the enhancement in photoactivity in the present system is due to the reduced band gap of TiOxSy alloy material. Such a band gap reduction is thought to be facilitated by the downward movement of the valence band of titanium disulphide which is made up of chalcogen atoms through substitution of sulphur atoms by oxygen atoms.
Synthesis and characterization of ZSM‐8‐type zeolite crystals
Authors: Joshi M. S. , Mohan Prabhu K.
Published: January 2007

Procedure for hydrothermal synthesis of ZSM‐8‐type zeolite crystals, using TEA—OH as a template, in the system having molar composition 16.2 (Na2O) — Al2O3 — 117 (SiO2) — 4.8 (TEA)2O — 3887 H2O at 170 °C is described. Results of characterization of these crystals by XRD, IR, EDAX, SEM, TGA, and adsorption studies are described and discussed. X‐ray diffraction studies establish that the crystals are ZSM‐8‐type with structure similar to that of ZSM‐5‐type crystals. Crystals have prismatic bipyramidal morphology with average size 18–25 microns. Degased calcined samples adsorb xylenes in the order p > m > 0. Pore length per unit cell, estimated from n‐hexane adsorption studies, is 46 Å.
Investigation on synthesis, characterization, and electronic behaviour of zinc oxide thin films in relation to fabrication of oxygen gas sensor
Authors: Arya S. P. S. , Srivastava O. N.
Published: January 2007

The zinc oxide thin films were prepared by spray pyrolysis method. The films were characterized by means of X‐ray diffraction and scanning electron microscopy techniques. The annealing treatment at 300 ± 30 °C for 15 and 30 hours improved the crystallinity of the film and also led to a homogeneous film surface. The O2 gas sensing properties of the zinc oxide thin film were studied by investigating the variation of the electrical resistance of the film as a function of O2 partial pressure at various temperatures. The gas sensing property was found to depend on the film characteristics in regard to its state of crystallinity and surface conditions. The gas sensing property was also dependent on the temperature at which the sensing was done. The optimum oxygen gas sensivity was obtained when the temperature of the zinc oxide sensor was maintained at 400 °C. The study reveals that sprayed zinc oxide thin films may be used as a low cost solid state oxygen gas sensor.
Characterization of plasma etching of molybdenum polycid conductor stacks in Cl2/CF4 and Cl2/CF4/O2
Authors: Handke R. , Lippert G.
Published: January 2007

The present paper is concerned with an extremly anisotropic two‐step patterning process for Mo2Si/poly‐Si double layers with an etch‐stop on thick P‐doped CVD‐SiO2. As etching gas Cl2/CF4/O2 and Cl2/CF4 are used. By means of etch rate dependencies, volatilities of possible reaction products and results, obtained from the literature it is attempted to develop a simple qualitative model on the chemism of the process.
Crystal structure of a newly oxidized aristolane sesquiterpenes, C15H22O3, from aristolochia debilis
Authors: Farag I. S. Ahmed , Kordy M. A. El , Kirfel A. , Will G.
Published: January 2007

Mr = 250, orthorhombic, P 212121, a = 9.583(6), b = 11.786(8), c = 12.298(9) Å, V = 1389.0 Å3, Z = 4, Dx = 1.20 g cm−3, F(000) = 544, MoKα, λ = 0.71069 Å, μ = 0.88 cm−1. Final R = 0.023 for 1006 observed reflections, T = 293 K. The structure was solved by direct methods and refined by full‐matrix least squares. It is an α, β unsaturated carbonyl compound with a trisubstituted double bonds. No significant variation in aromatic bond lengths. The strain affecting the molecule is largely due to angular deformation which is partly due to the fusion of the rings and partly due to substitution of H‐atoms by methyl groups and oxygen atoms.
Influence of penetration velocity and temperature by microindentation of NaCl single crystals
Authors: Boyarskaya Yu. S. , Grau P. , Zhitaru R. P. , Kluge G.
Published: January 2007

The kinetic of formation of microhardness indentations on NaCl‐single crystals has been investigated. The indentation was performed dynamically by a new recording technique, allowing to use different penetration velocities at distinct deformation temperatures. The characteristical indentation parameters are dependent on velocity and temperature in a partially complicated way showing the simultaneous action of different thermal activated deformation processes.
Interference pattern of X‐ray waves inside the crystal and its image in vacuum in double‐field approximation (II)
Authors: Aslanian V. G. , Bezirganian H. P. , Bezirganian P. H.
Published: January 2007

The energy flows of the X‐ray waves, diffracted in thick crystals in double‐field approximation, have been examined. It has been demonstrated that in a symmetric Laue case the energy flows in the upper layers are oriented in the direction of incidence and reflection, whereas in the lower layers they are oriented in the direction of the normal to the entrance surface of the crystal. The formation of pendular bands during diffraction of X‐rays in thick parallelepiped and wedge‐shaped crystals has been investigated. A method for obtaining pendular bands from such crystals is described.
Growth of hollow Bi2Se2S crystals from vapour
Authors: Arivuoli D. , Gnanam F. D. , Ramasamy P.
Published: January 2007

Hollow crystals of Bi2Se2S have been grown from vapour. Crystals show open lateral surface and the length of the crystals is 6 to 7 mm. An explanation is given for the growth mechanism of the hollow crystals.
Growth of Te(OH)6Na2HPO4 · H2O single crystals in silica gel and their characterization
Authors: Devanarayanan S. , Kalkura S. Narayana
Published: January 2007

Single crystals of Te(OH)6Na2HPO4 · H2O were grown in silica gel medium using single‐test tube diffusion method. Hexagonal pyramidal and hexagonal tabular single crystals were obtained. Crystals were characterized by IR, X‐ray, and Raman studies.
Effect of purification on the polytypism in solution‐grown cadmium iodide crystals
Authors: Chaudhary S. K. , Trigunayat G. C.
Published: January 2007

The effect of purification on the polytypism in cadmium iodide crystals has been studied by X‐ray diffraction in three hundred and sixty polytypes. Formation of small period polytype 2H is governed by both temperature and impurities contained in the starting material. 4H is the most stable polytype and higher occurrence of unidentified polytypes in crystals of purified material has been attributed to free movement of edge dislocations during growth. The results have been examined against empirical conclusions of earlier investigations.
X‐ray diffraction in thick perfect crystals with deformed subsurface layers
Authors: Bezirganyan P. H. , Aboyan A. O. , Tumasyan A. S.
Published: January 2007

The diffraction of X‐rays in thick perfect crystals with deformed subsurface layers has been investigated. It was shown that the kinematic scattering of X‐rays took place in deformed layers, while the dynamical one occurred in the perfect part of the crystal, ‐its bulk; also, that in beams of X‐rays diffracted on surface defects, the role played by the second harmonics of the applied characteristic radiation MoKα1 was essential.