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  • 1970-1974  (8)
  • 1
    Electronic Resource
    Electronic Resource
    High-voltage transmission scanning electron microscopy (1970)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 3 (1970), S. 49-59 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The use of scanning electron microscopy for the study of thin specimens by transmission has advantages over conventional transmission electron microscopy in terms of simplicity and cheapness, reduction in damage to irradiation-sensitive specimens and convenience for electron diffraction, energy analysis and the electronic measurement and recording of images. These advantages are specially important for microscopes operating in the range 200 kV to 1 MeV. The design of a 600 kV instrument to exploit these advantages is described. The possible modes of operation employing deflexion systems and an energy analyser are discussed with reference to light- and dark-field microscopy, convergent beam diffraction and conventional focused diffraction patterns. The reciprocity principle is invoked to relate both image contrast and instrument design in scanning electron microscopy to that in conventional transmission electron microscopy. Examples are given of light- and dark-field images and diffraction patterns obtained with the instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889870005642
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Line patterns in wide-angle convergent beam electron diffraction (1971)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 4 (1971), S. 482-487 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Wide-angle convergent-beam electron diffraction patterns from thin single crystals show sets of parallel lines somewhat similar to Kikuchi or Kossel lines. In some cases, each line separates into a black and white line pair when the electron beam is defocused. It is shown that this separation depends on the curvature of the crystal. A method for analysis of the line geometry is proposed which takes into account the aberrations of the electron lens. Using a high-voltage transmission scanning electron microscope, through-focus series of patterns from graphite crystals have been obtained and analyzed to give values for the radius of curvature of the crystal. In defocussed patterns the distortions of the lattice by defects are clearly visible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889871007507
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Short-range ordering of vacancies and Fermi surface of TiO (1971)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 376-383 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of the disordered (high-temperature) phase of titanium monoxide has been studied by electron diffraction. Composition-dependent complex distributions of diffuse scattering are observed and interpreted in terms of short-range-ordered configurations of lattice vacancies. The proposition that the form of the diffuse scattering may correspond to ordering under the influence of long-range electronic energy terms and so show a direct relationship to the topology of the Fermi surface is examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739471000834
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Comments on the BJR theory of electron diffraction (1970)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 26 (1970), S. 152-153 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: In the BJR theory of electron diffraction an absorption effect due to weak beams is introduced into the two-beam approximation for the dynamical diffraction of electrons by thick crystals. This is shown to be unjustified for diffraction from perfect crystals. The use of the theory to derive the temperature dependence of diffraction intensities must therefore be modified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739470000232
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    High-resolution dark-field electron microscopy. II. Short-range order in crystals (1973)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 29 (1973), S. 537-540 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The simple theory for the intensity distributions in high-resolution dark-field electron microscope images of thin specimens, derived from the phase-object approximation, is applied to discussion of images obtained from the diffuse scattering in electron diffraction patterns from crystals having short-range ordering of atoms on the lattice sites. It is shown that interpretation of the intensity distribution in terms of images of 'microdomains' is not usually justified. It is necessary to take into account the statistics of superposition of defects, possible dynamical diffraction effects and the fact that both positive and negative deviations from the average value of projected potential may give intensity maxima. Examples used to illustrate these points include a hypothetical case of a disordered CuAu crystal and some experimental observations of disordered LiFeO2 showing a resolution of details on an atomic scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739473001336
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    High-resolution dark-field electron microscopy. I. Useful approximations (1973)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 29 (1973), S. 529-536 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Simple expressions are derived for the form of the intensity distributions in high-resolution dark-field electron micrographs of thin specimens for which the phase-object approximation may be applied. For cases in which the phase change of the electron wave can be assumed to be small it is shown that there is an optimum defocus value which gives the best, interpretable resolution. For dark-field images obtained either with a central beam stop or with a tilted incident beam, the image intensity is shown to depend on the square of the deviation of the projected potential from an average value. The further complications resulting when the phase change cannot be assumed small are discussed and illustrated by means of a simple example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739473001324
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Periodicity in thickness of electron-microscope crystal-lattice images (1973)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 29 (1973), S. 710-714 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: High-resolution electron micrographs of crystal lattices showing a recognizable correlation of intensity with atom positions are normally obtained only for very thin crystals (less than about 100 Å thick). For some crystals of niobium and titanium-niobium oxides, it has been observed that this thin-crystal contrast is repeated for thicknesses of the order of 1000 Å. This is regarded as evidence that under conditions of high symmetry of excitation, the wave field in the crystal is essentially periodic with distance in the beam direction if a particular relationship exists between the structure amplitudes and the excitation errors for the diffraction process. This is confirmed by calculations made for f.c.c. lattices with Cu, CuAu3, or Au atoms and for a range of wavelengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739473001737
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    High resolution electron microscopy of tourmaline crystals (1973)
    Springer
    Mineralogy and petrology 20 (1973), S. 216-224 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Hochauflösende Elektronen-Mikrographien wurden von zwei Typen von Turmalinkristallen, die auf einer Goniometereinrichtung so orientiert waren, daß der Elektronenstrahl parallel zurc-Achse verlief, erhalten. Bilder mit einer 3 Å-Auflösung, die entfokusiert aufgenommen wurden, geben direkte Hinweise auf die Atomanordnung; sie deuten auf Ordnung mittlerer Reichweite der Metallatome in Buergerit und zeigen unerwarteterweiseh31l-Symmetrie bei Elbait-Schörl-Mischkristallen. Das Auftreten von Ordnung wird als vermutlicher Elektronenbestrahlungseffekt gedeutet.
    Notes: Summary High resolution electron micrographs have been obtained from crystals of two types of tourmaline, aligned in a goniometer stage so that the electron beam is parallel to thec axis. Images having a resolution of about 3 Å taken out of focus show direct indications of the atomic arrangement; they suggest medium-range ordering of the metal atoms in buergerite and unexpectedh31l symmetry in elbaite-schorl solid solution. The appearance of ordering is tentatively explained in terms of electron-irradiation effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081921
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