Physics and Chemistry of Minerals

, Volume 10, Issue 2, pp 47–54 | Cite as

Investigation of superstructures in mullite by high resolution electron microscopy and electron diffraction

  • J. Ylä-Jääski
  • H.-U. Nissen
Article
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Abstract

Superstructures in synthetic mullite, Al4+2xSi2−2xO10−x, prepared using the zone melting technique, are studied by high resolution electron microscopy (HREM), electron diffraction, and in situ energy dispersive X-ray spectroscopy. For x=0.40 composition HREM images indicate only short-range order. Near x=0.5 composition mullite has an antiphase domain structure with antiphase boundaries (APB's) oriented parallel to (100). For higher Al-content the APB's run in non-rational orientations which are slightly inclined against the {601}-planes. We propose models for the superstructures in which oxygen vacancies are arranged in channels parallel to the crystal b-axis. The models are supported by a one-to-one match between observed and computer-simulated images. An Al-rich limit of x=2/3 for mullite is deduced on the basis of stereochemical considerations. Different ordering schemes for the tetrahedral cations are believed to result in the orientation change of the APB's near x=0.5 composition.

Keywords

Oxygen Vacancy Electron Diffraction Zone Melting Orientation Change Oriented Parallel 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag 1983

Authors and Affiliations

  • J. Ylä-Jääski
    • 1
  • H.-U. Nissen
    • 1
  1. 1.Laboratorium für FestkörperphysikEidgenössische Technische Hochschule, HönggerbergZürichSwitzerland

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