bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoconductivity of Anisotropically Deformed Intrinsic Germanium
Authors: Romanov V. A. , Zhadko I. P. , Boiko I. I. 
Published: July 2007

AbstractTheoretical and experimental investigations are made of the photoconductivity in anisotropically deformed germanium in conditions favourable to the occurrence for electrical pinch. A saturation of the photocurrent for sufficiently high electric fields is predicted and observed. The effect of the electric field on the spatial distribution of the carriers in an illuminated crystal is investigated using the infrared spot method. Similar values of the surface recombination velocities are obtained from the current‐voltage and relaxation characteristics.
Mössbauer Effect in α‐Fe2O3
Authors: van der Woude F. 
Published: July 2007

AbstractExperimental data are obtained for the antiferromagnetic compound α‐Fe2O3 by the Mössbauer technique. α‐Fe2O3 exhibits interesting properties, viz. the quantization axis of the spins of the iron ions changes direction by 90° at Tt = 260 °K, and the between 260 °K and the Néel temperature of 956 °K it shows weak ferromagnetism. The changes of the internal fields at the transition temperature are studied in detail. The effective magnetic field Heff drops abruptly by 8 kOe on heating α‐Fe2O3 through the transition temperature. Furthermore, the curve of Heff against T shows temperature hysteresis around Tt. An explanation for the discontinuity in Heff at Tt can be given on the basis of a small asymmetry of the charge distribution of the 3d‐electrons of the Fe3+ ions; this produces a contribution on the effective magnetic field of the orbital and spin magnetic moments of these electrons which is in addition to the contact field. The temperature dependence of Heff is also determined and cannot be described in terms of a Brillouin curve for S = 5/2.
Studies on the Electrical Properties of Uranium Oxides II. Non‐stoichiometric U3O8
Authors: Singh N. , Karkhanavala M. D. 
Published: July 2007

AbstractThe electrical conductivity σ and Hall coefficient RH are measured over the range 250 to 400 °K on pellets of U3O8 sintered for different periods up to 120 h at 900 °C. The sintering results in a progressive decrease of the O/U ratio from 2.666 to 2.63 accompanied by an increase in the density from 5.62 (“green” density) to 8.08 g/cm3. The values of the electrical conductivity are corrected for porosity. With decreasing O/U ratio, the conductivity and Hall mobility increase, while the conductivity activation energy decreases. The results for the highly sintered (96.5% of theoretical density) material of composition UO2.63 are interpreted on the basis of the hopping of small polarons.
Screw Dislocations in and near Lamellar Inclusions
Authors: Chou Y. T. 
Published: July 2007

AbstractUsing the method of images, the stress field of a screw dislocation in and near a lamellar inclusion is determined. The general solution holds for many simple cases involving straight boundaries, such as metals with surface film, thin plates, or composite materials of laminated structure. The image force on the dislocation is derived and discussed in terms of the thickness and rigidity of the inclusion.
Crystal Growth Measurements on Potassium Aluminium Alum and Sodium Chlorate from Slightly Supersaturated Solutions
Authors: Bennema P. 
Published: July 2007

AbstractMeasurements of the rate of growth R of a potassium aluminium alum crystal and a sodium chlorate crystal are presented. For alum, when the relative supersaturation σ lies between 3 × 10−5 and 10−2, R is found to be proportional to σ but for σ greater than 10−2 when spontaneous nucleation occurs, some points (showing considerable scatter) are obtained which lie above the linear curve. For sodium chlorate in the range 3 × 10−5 ⪅ σ ⪅ 5 × 10−4 a distinctly non‐linear (nearly parabolic) (R, σ) law is observed and for the range 5 × 10−4 ⪅ σ ⪅ 1.5 × 10−3 a linear curve is found which upon extrapolation to low values of σ does not pass through the origin. The theoretical (R, σ) curve resulting from the surface diffusion model of Burton, Cabrera, and Frank [1, 2] fits the measured (R, σ) points of sodium chlorate in a satisfactory way. It follows from the experiments that R does not depend on the velocity of flow of the solution.
Crystal Field Calculation in the CdWO4 Lattice
Authors: Kubec F. 
Published: July 2007

AbstractThe components of the crystal field potential at a cadmium site in CdWO4 are evaluated using the point charge model and taking into account the effect of induced dipoles. The calculation is carried out in the direction of the magnetic z axis of Cu2+ in CdWO4 and Fe3+ in ZnWO4 by summing the monopoles up to 25000 and dipoles up to 1000. It is found that the dipolar contribution is substantial and alters the sign of the crystalline field component obtained from point‐charges only. As the value of this contribution is rather large, it is neccessary to take into account the covalency effect of the crystal and to reduce the charges of the diamagnetic ions. The ground state wave function of Cu2+ and the zero field splitting of Fe3+, determined from experiments, are in reasonable agreement with those obtained by this calculation.
Zum Epitaxieverhalten dünner Silberaufdampfschichten
Authors: Jahrreiss H. , Isken H. ‐J. 
Published: July 2007

AbstractAuf Steinsalzspaltflächen wurden Silberschichten verschiedener Dicke unter genauer Temperaturkontrolle aufgedampft und nach Ablösung von der Unterlage mittels Elektronenbeugung in Durchstrahlung untersucht. Die Aufdampfraten wurden dabei in sehr kleinen Schritten variiert, und es ergab sich für jede Temperatur T eine kritische Aufdampfrate Rk, bei der ein nahezu sprunghafter Übergang von rein monokristalliner Orientierung zu nur noch teilweiser Ausrichtung erfolgt. Der Funktionszusammenhang Rk(T) ermöglicht eine Bestimmung der Platzweschselenergie der Ag‐Atome auf der Oberfläche und stimmt überein mit der Modellvorstellung, daß mit der Ausbildung von Ag‐Atompaaren auf der NaCl‐Oberfläche ohne Möglichkeit vorherigen Platzwechsels in energetisch günstige Positionen eine vollständige Monokristallausrichtung nicht mehr zustandekommt.
AC Measurements on Hard Superconductors
Authors: Ullmaier H. A. 
Published: July 2007

AbstractCylindrical samples of PbIn, NbZr, and NbTa were exposed to a longitudinal, static magnetic field with a collinear alternating field, and the voltages produced in pick up coils wound around the samples were observed on an oscilloscope. The shape of the voltage‐time curves can be adequately explained by considering a surface sheath which is able to carry a certain critical surface current and a bulk region where the pinning forces dominate the magnetic behavior. It is shown that an analysis of the voltage‐time curves obtained yields values for the critical surface current and the bulk critical current density which are in good agreement with static measurements. While the bulk critical current density goes to zero when the external field reaches the upper critical field Hc2, the surface currents can be seen up to a field Hc3 > Hc2. Values of the bulk critical current density obtained were then used to determine the pinning force per unit volume and the pinning force on a single vortex line, as a function of the vortex line density.
Charge of Dislocations in Pure and γ‐Irradiated LiF
Authors: Rueda F. , Dekeyser W. 
Published: July 2007

AbstractThe electrical charge of newly created dislocations in non‐irradiated and γ‐irradiated LiF is studied by the indentation method. In both cases the dislocations are negatively charged. Subsequent annealing after irradiation produces a reversal of sign of that charge, the first isoelectric temperature being located in the range of bleaching of F‐ and M‐centres. These effects are attributed to negative vacancies produced by irradiation and thermal bleaching.
Theorie des Dielektrizitätstensors in Relaxationszeit‐Approximation
Authors: Mertsching J. 
Published: July 2007

AbstractIm Rahmen der “random phase approximation” wird mit Hilfe des statistischen Operators der Elektronen die Stromdichte berechnet, die durch ein elektromagnetisches Feld in einem Festkörper induziert wird. Dabei wird in der Bewegungsgleichung für den statistischen Operator der Stoßterm durch ein Relaxationsglied approximiert und die Gleichgewichtsverteilung derart gewählt, daß Stromdichte und Ladungsdichte eichinvariant sind und der Kontinuitätsgleichung genügen. Aus der induzierten Stromdichte lassen sich der komplexe Dielektrizitäts‐ und Permeabilitätstensor für beliebige Wellenvektoren q und Frequenzen ω, wenn auch bezüglich der transversalen Komponenten im allgemeinen nicht völlig eindeutig, bestimmen. Im Grenzfall q → 0 ist der Dielektrizitätstensor ϵ(ω) eindeutig bestimmt und setzt sich aus dem Intraband‐Drude‐Term sowie Interbandtermen zusammen, die verglichen mit den von Ehrenreich und Philipp 1962 angegebenen den zusätzlichen Faktor (1 + magnified image) enthalten, wobei τνν′ eine Interband‐Relaxationszeit ist.
Diffusion von Sn und Zn in Sn und in einer homogenen Sn‐Zn‐Legierung
Authors: Bergner D. , Lange W. 
Published: July 2007

AbstractNeben Ergebnissen methodischer Untersuchungen über die Anwendbarkeit der Fisherschen Methode zur Messung von Korngrenzendiffusionskoeffizienten werden die Ergebnisse von Messungen der Volumendiffusion von Sn und Zn und der Korngrenzendiffusion von Sn in Sn und in einer homogenen Sn‐Zn‐Legierung mit 0,5 Gew.% Zn mitgeteilt.
Twinning deformation in iron at 4 °K
Authors: McRickard S. B. 
Published: July 2007

AbstractFine grained, Ferrovac iron has been found to deform in a discontinuous manner when tested in tension at 4.2 °K. The deformation has been found to be a unique continuous twinning process which is initiated by a critical stress of 137000 psi and from which a uniform strain energy release of 0.01 eV/mol for each twinning event has been calculated. The characteristics of this twinning deformation are discussed and comparisons with other reported low temperature phenomena are made.
Zum linearen Anklingen der Photoleitfähigkeit in Halbleitern
Authors: Egorov V. D. 
Published: July 2007

AbstractEs wird der Einfluß der Oberflächenrekombination und einer parasitären Kapazität auf den Anfangsteil des Anklingens des Photosignals betrachtet. Die Ergebnisse ermöglichen Aussagen über die Verwendbarkeit eines Germanium‐Photowiderstandes zur Messung der Intensität von Lichtimpulsen.
Radiation‐induced point defect clusters in copper and gold
Authors: Merkle K. L. 
Published: July 2007

AbstractThe transmission electron microscope technique was used to investigate the defect structures introduced by bombardment of thin films of copper and gold with heavy particles. The black spot defects in gold can be shown to be produced directly in displacement cascades if the energies of the cascades are high enough. The size of the observed defect clusters increases with increasing primary energy. A very energetic primary can produce a bunch of closely spaced defect clusters. Charged particle irradiations of copper indicate that contrary to gold not every primary event above a certain threshold energy is observed. This is interpreted as being due to the formation of non‐overlapping subcascades, each of which might form a stable cluster but is generally too small to be observed under our experimental conditions. Those clusters in copper and gold that have been identified unambiguously are of vacancy type.
Radiation damage and xenon release in quartz and fused silica following ion bombardment
Authors: Matzke Hj. 
Published: July 2007

AbstractSingle‐crystalline quartz and fused silica were bombarded with 40 keV xenon ions to give integrated ion doses of up to 2 × 1016 ions/cm2. At low dose (8 × 1010 ions/cm2) diffusional release processes dominated with activation enthalpies of 58 and 61 kcal/mol for quartz (diffusion along and perpendicular to the c‐axis respectively) and 72 kcal/mol for fused silica. Diffusion in the amorphous phase was markedly slower than diffusion in the crystalline phase. At doses ≧ 4 × 1013 ions/cm2 radiation damage in the form of a phase change to a quasi‐amorphous state occurred in quartz, as revealed by reflection electron diffraction. The annealing of this structural damage coincided with enhanced thermally activated gas release at temperatures below those of volume diffusion. Fused silica showed a similar enhanced release at high bombardment dose. Thus, the quasi‐amorphous phase produced by ion bombardment is different from that of fused silica. The present results indicate further, in agreement with the literature on neutron irradiated quartz and fused silica, that both materials approach a common state at a high level of radiation damage.
Strahleninduzierte Phasenumwandlungen einiger Substanzen des Perowskit‐Gittertyps und ihre thermodynamische Behandlung
Authors: Hauser O. , Schenk M. 
Published: July 2007

AbstractEs werden experimentelle Ergebnisse über die thermischen und strahleninduzierten Phasenumwandlungen sowie über die Verschiebung der Umwandlungstemperaturen zwischen den Raum‐ und Hochtemperaturphasen von BaTiO3, PbZrO3 und PbTiO3 bekanntgegeben. Es wurden vorwiegend röntgenographische und kalorimetrische Untersuchungen durchgeführt. Für die Deutung der erzielten Ergebnisse werden strukturelle und thermodynamische Überlegungen herangezogen. Dabei zeigt sich, daß die strahleninduzierten und thermischen Phasenumwandlungen im Rahmen einer thermodynamischen Betrachtungsweise gemeinsam behandelt werden können.
Über den Begriff „aktives Gleitvolumen”︁ und dessen Bedeutung
Authors: Schwink Ch. 
Published: July 2007

AbstractDer Begriff „aktives Gleitvolumen”︁ bzw. „aktive Kristallänge”︁ wird in die Plastizitätslehre eingeführt. Er spielt eine wesentliche Rolle, wenn das aktive Gleitvolumen von den äußeren Verformungsparametern, Geschwindigkeit und Temperatur, abhängt. Das ist im allgemeinen dann zu erwarten, wenn Gleitvorgänge thermisch aktiviert ablaufen. Aus einer energetischen Überlegung wird eine Näherungsformel für die Abhängigkeit des aktiven Gleitvolumens von der Abgleitgeschwindigkeit gewonnen. Sie beschreibt die bisher vorliegenden experimentellen Ergebnisse. Folgerungen für die Analyse thermisch aktivierter Vorgänge, die sich aus der Veränderlichkeit des aktiven Gleitvolumens ergeben, werden kurz besprochen.
Colour centres in KCl doped with Zn+2, Cd+2, and Hg+2
Authors: Ben‐Dor L. , Glasner A. , Zolotov S. 
Published: July 2007

AbstractThe absorption spectra of additively coloured Zn+2, Cd+2 and Hg+2 doped KCl indicate the formation of monovalent as well as neutral atomic centres. The formation of these centres follows the trapping of electrons by the metal ions added to the KCl.
Elektronenmikroskopische Oberflächen‐ und Durchstrahlungsuntersuchungen von Eisen‐Einkristallen sowie der Einfluß der Orientierung auf deren Verfestigungsverhalten
Authors: Bilger H. 
Published: July 2007

AbstractDie Verfestigungskurven mittelorientierter Eisen‐Einkristalle können durch 3 Verfestigungsbereiche charakterisiert werden. Oberflächenbeobachtungen lassen im Bereich I überwiegend Einfachgleitung, im Bereich II Mehrfachgleitung erkennen. Die Laufwege der Schraubenversetzungen sind in beiden Bereichen kleiner als diejenigen der Stufenversetzungen. Im Bereich III findet die Abgleitung innerhalb welliger Gleitbänder statt. Die von Beginn an starke Verfestigung randorientierter Kristalle wird durch Mehrfachgleitung verursacht.
Study of energy transfer from 3d to 4f electrons in antiferromagnetic MnF2: Eu3+ crystals
Authors: Eremenko V. V. , Matyushkin E. V. , Petrov S. V. 
Published: July 2007

AbstractThe spectrum and luminescence intensity of the antiferromagnetic crystals MnF2:Eu3+ are investigated experimentally for temperatures between 20 and 90 °K. This range includes the magnetic ordering temperature TN (≈ 68 °K). At the temperature TH (≈ 0,5 TN), corresponding to the spin ordering of the excited Mn2+ ions, the luminescence intensity due to these ions shows a sudden increase while the luminescence intensity due to the Eu3+ ions suffers a sudden decrease. This indicates that an anomalous change occurs in the transfer of energy between the Mn2+ and Eu2+ ions due to the condensation of the local magnetic vibrations of the optically excited Mn2+ ions.
Solution hardening in niobium
Authors: Harris B. 
Published: July 2007

AbstractA study has been made of the solution hardening of niobium by tantalum, vanadium, zirconium, and tungsten. It is found that hardening is linear with composition at small concentrations and is simply related to the sum of the atomic size and elastic modulus differences. Agreement with the solution‐hardening model of Fleischer for f.c.c. metals is not exact, however, for the results indicate that the atomic size mismatch, rather than the elastic modulus difference, is the dominant factor in hardening. – Strain‐hardening, strain‐rate sensitivity, and temperature dependence of the flow‐stress are studied, and it is shown that the basic deformation mechanism remains unaltered by solute additions. It is suggested that the solutes raise the long‐range, athermal component of the flow‐stress and reduce the short‐range, thermally‐activated component.
Kriechexperimente an hochreinen Kupfer‐Einkristallen
Authors: Schmid G. 
Published: July 2007

AbstractNach der Methode der stufenweisen Belastung wurden Kupfer‐Einkristalle mit der Reinheit 99,999% bei 78 °K und bei Zimmertemperatur verformt. Neben dem zeitlichen Kriechgesetz wurde auch die Abhängigkeit der Abgleitgeschwindigkeit von der Temperatur und der Schubspannung mit Hilfe von Temperatur‐ und Lastwechseln gemessen. Die nach Schoeck durchgeführte Analyse der thermisch aktivierten Prozesse zwingt zu der Annahme, daß die Versetzungen häufig Rücksprünge ausführen und daß ein Spektrum von Hindernissen vorliegt. Aus dem Aktivierungsvolumen und der freien Aktivierungsenthalpie lassen sich die Versetzungsdichten in Abhängigkeit von der Verformung abschätzen. Der Vergleich mit den elektronenmikroskopisch gewonnenen Werten von Eßmann liefert eine recht befriedigende Übereinstimmung und zeigt, daß das Schneiden der Waldversetzungen geschwindigkeitsbestimmend ist.
Calculation of the mean inner potential of a crystal in the statistical theory
Authors: Anishchenko R. I. 
Published: July 2007

AbstractThe mean inner potential of a crystal is calculated for 49 different metals by using the Thomas‐Fermi‐Dirac model of a compressed atom. The dependence of the mean inner potential on the atomic number Z has a distinctly periodic character. The effect of the exchange interaction and the conduction electrons on the potential are taken into account. A comparison with experimental data shows good agreement for the heavy elements.
Adiabatic, Isothermal, and Intermediate Pressure Derivatives of the Elastic Constants for Cubic Symmetry. II. Numerical Results for 25 Materials
Authors: Barsch G. R. , Chang Z. P. 
Published: July 2007

AbstractThe purely adiabatic and the purely isothermal pressure derivatives of the elastic constants are calculated from the experimentally determined mixed isothermal‐adiabatic pressure coefficients of the elastic constants for 24 cubic crystals and one isotropic material. Also the linear combinations of the third‐order elastic constants that can be determined from these data are given for the different thermodynamic conditions. The first two expansion coeffcients of the volume versus pressure relation were determined from the ultrasonically measured elastic constants and their pressure coefficients and compared with Bridgman's high pressure volumetric data.
Vacuum Heat Treatment of CdS Single Crystals
Authors: Böer K. W. , Kennedy C. A. 
Published: July 2007

AbstractChanges of the spectral distribution of photoconductance and conductance glow curves after heat treatment between 370 and 620°K and immediate quenching of undoped CdS single crystal platelets in ultrahigh vacuo are described. After annealing, the electrical properties after heat‐treatment quenching sequences are largely reproducible. The results are interpreted as the dissociation of larger defect associates containing Cd vacancies and consequent production of single Cd vacancies causing a trap level at Ec – Et ≈︁ 0.4 eV and vacancy pairs with trap levels at Ec – Et ≈︁ 0.95 eV. Dissociation and stress enhanced diffusion of vacancies in the neighborhood of associates becomes noticeable at treatment temperatures above 350°K.
On the Scattering Processes in Semiconductors
Authors: Kołodziejczak J. 
Published: July 2007

AbstractThe scattering processes in semiconductors are analysed for the purpose of the solution of a non‐linear Boltzmann equation. The collision term in the Boltzmann equation is calculated for acoustic modes, and for polar and non‐polar optical modes. The differential collision operators are obtained for the isotropic part of the distribution function. The calculations are carried out assuming possible nonparabolicity of the energy band.
Messung von Versetzungsgeschwindigkeiten in Germanium
Authors: Schäfer S. 
Published: July 2007

AbstractDie Versetzungsgeschwindigkeit in Ge wird an Halbringen gemessen, deren Durchstoßpunkte an der Oberfläche mit einem Ätzmittel sichtbar gemacht werden. In der Nähe des einen Durchstoßpunktes hat der Versetzungshalbring Schrauben‐, in der Nähe des anderen 60°‐Charakter. Die Halbringe sind nicht stabil und können nur mit Hilfe einer Vorspannung in ihrer Ausgangslage gehalten werden. Die Versetzungsgeschwindigkeit wurde zwischen 220 und 580°C gemessen und hängt von der Temperatur T und der Spannung τ wie \documentclass{article}\pagestyle{empty}\begin{document}$ v = B_n \left({\frac{\tau }{{\tau _0 }}} \right)^m {\rm exp}\left({ - \frac{Q}{{kT}}} \right)$\end{document} ab. Es ist Q = 1,62 eV für Schrauben‐ und 60°‐Versetzungen; m ergibt sich zu 1,0 für Schraubenversetzungen und zu 1,2 für 60°‐Versetzungen‐Ferner ist Bn = 108 mm/s und τ0 = 1 kp/mm2.
On the Theory of Galvanomagnetic Phenomena in Strong Electric Fields
Authors: Kolodziejczak J. 
Published: July 2007

AbstractSome galvanomagnetic effects are calculated for electric fields which are sufficiently high to give quadrac tideviations from Ohm's law. The calculations are carried out assuming nonparabolicity of the energy band. Acoustic mode scattering, and polar and non‐polar optical mode scattering are included in the analysis. Kane's model of the nonparabolic band is used in the final result.
Dependence of the Ion–Electron Emission Coefficient on the Angle of Incidence
Authors: Evdokimov I. N. , Mashkova E. S. , Molchanov V. A. , Odintsov D. D. 
Published: July 2007

AbstractThe dependence of the ion‐electron emission coefficient on the angle of incidence is studied for targets of polycrystalline metals (Cu, Ag, Mo, Zr, W, Bi), and a graphite target, bombarded with 25 to 30 keV noble gas and nitrogen ions. The application of a magnetic field parallel to the axis of rotation shows that both the positive and negative ion currents to the collector are negligibly small. The emission coefficient increases as the angle of incidence increases up to angles of about 80 to 85°. Up to a certain limiting angle (from 36 to 81° for different ion‐target combinations) the angular dependence may be approximated by a reciprocal cosine law, while for larger angles the variation is rather slower. Comparisons are made, calculations based on the transparency model.
Microstrain Region and Transition to Macrostrain in 99.9% Polycrystalline Copper
Authors: Man J. , Holzmann M. , Vlach B. 
Published: July 2007

AbstractA study is made of the effect of grain size and substructure on the microstrain region and on the transition to the macrostrain region. The results do not agree with the conclusions obtained from the Brown‐Lukens theory. The possibility of using statistical theory to describe the stress‐strain dependences in the microstrain region is considered.