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Structural Studies Of Al55 Si7Cu25.5 Fe12.5 1/1-Cubic Approximant By Means Of X-Ray Rietveld, Method And Haadf-Stem

Published online by Cambridge University Press:  10 February 2011

H. Yamada ,
T. Takeuchi ,
U. Mizutani  and
N. Tanaka
H. Yamada
Affiliation:
Department of Crystalline Materials Science, Nagoya University, Nagoya 464–8603, JAPAN, mizutani@nuap.nagoya-ud.ach.jp
T. Takeuchi
Affiliation:
Department of Crystalline Materials Science, Nagoya University, Nagoya 464–8603, JAPAN, mizutani@nuap.nagoya-ud.ach.jp
U. Mizutani
Affiliation:
Department of Crystalline Materials Science, Nagoya University, Nagoya 464–8603, JAPAN, mizutani@nuap.nagoya-ud.ach.jp
N. Tanaka
Affiliation:
Department of Applied Physics, Nagoya University, Nagoya 464–8603, Japan
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Abstract

By combining the powdered x-ray Rietveld analysis and the High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM), we have made the detailed structural analysis for the Mackay-type Al55Si7Cu25.5Fe12.5, 1/1-cubic approximant. Electron diffraction measurements revealed its space group to be Pni3. Both position and occupancy in every atomic site are refined by means of the Rietveld analysis. The factors Rwp and Riwhich are taken as measures for the precision of the Rietveld analysis, are reduced to 2.57 and 3.89 %, respectively. The refined structure of this approximant is a simple cubic with the lattice constant of 12.31916(2) Å. Two different icosahedral clusters consisting of triply stacked atomic shells exist at the vertex and body centered positions in the CsCl-type unit cell. In addition, we propose that there exists most likely a “structural disorder” in the first shell of the cluster in one of the sublattices. The HAADF images taken along [100] and [111] directions agree with the projection images calculated from the Rietveld-refined structure, lending a strong support to the validity of the present atomic structure model deduced from the Rietveld analysis.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 553: Symposium LL – Quasicrystals , 1998 , 117
Copyright
Copyright © Materials Research Society 1999

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References

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