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Irreversible Structural Transformation of five fold i-AlPdMn Quasicrystals after Ion Bombardment and Annealing
Ames Laboratory Conference Papers, Posters, and Presentations
  • Frank Schmithüsen, European Synchrotron Radiation Facility
  • Giovanni Cappello, Centre national de la recherche scientifique
  • S. Decossas, European Synchrotron Radiation Facility
  • G. Torricelli, European Synchrotron Radiation Facility
  • T.-L. Lee, European Synchrotron Radiation Facility
  • Marc de Boissieu, LTPCM INPG
  • Y. Calvayrac, Centre national de la recherche scientifique
  • Thomas A. Lograsso, Iowa State University
  • Fabio Comin, European Synchrotron Radiation Facility
  • Joël Chevrier, Centre national de la recherche scientifique
Document Type
Conference Proceeding
MRS Fall Meeting & Exhibit
Publication Date
(42.3584308, -71.0597732)
Five fold i-AlPdMn surface prepared under UHV by ion bombardment and annealing was so far considered to be bulk terminated. This result was substantially based on a quantitative LEED analyses [1]. Analysis of the specular rod in a X ray diffraction experiment at grazing incidence supported this result [2]. We present a new study of this surface by high resolution X ray diffraction at normal incidence. In this Bragg configuration the diffraction peak 18 – 29 for instance is at a photon energy of 2.873keV, the 72 – 116 reflection at 5.725keV. This results in an analyzed thickness of the sample surface of a few micrometers. The surface was cleaned by ion bombardment. During annealing (T≅880K), we clearly observed the progressive disappearance of the initial Bragg peak characteristic of the as cast bulk sample. Conversely a new Bragg peak grows at an energy position shifted by 1eV compared to the position of the original Bragg peak. This is a clear signature for an irreversible structural transformation which takes place on at least the micron thickness. On the transformed surface, both, a LEED pattern and a RHEED pattern, characteristic for a five fold surface were easily obtained. This high resolution experiment (the relative Bragg peak shift is 3ׁ10−4) was reproduced on samples from different initial compositions. This shows that five fold i-AlPdMn surface changes after preparation by ion bombardment and annealing at 900K on a micrometer thickness. This is not consistent with the conclusion that the surface is simply terminated by a cut of the original bulk. We conclude that a reorganization process of the quasicrystalline structure during annealing proceeds in the surface vicinity (probed depth is close to a few microns).

This article is from MRS Proceedings 643 (2000): K11.4.1, doi:10.1557/PROC-643-K11.2 .

Copyright Owner
Materials Research Society
Citation Information
Frank Schmithüsen, Giovanni Cappello, S. Decossas, G. Torricelli, et al.. "Irreversible Structural Transformation of five fold i-AlPdMn Quasicrystals after Ion Bombardment and Annealing" Boston, MA(2000)
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