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X-Ray Determination of Site Occupation Parameters in Ordered Ternaries Cu(Aux.M1x.)M = Ni,Pd

Published online by Cambridge University Press:  26 February 2011

R. Kumar ,
C. J. Sparks ,
T. Shiraishi ,
E.D. Specht ,
P. Zschack ,
G. E. Ice  and
K. Hisatsune
R. Kumar
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831
C. J. Sparks
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831
T. Shiraishi
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 Kyushu University, Higashi-ku, Fukuoka 812, Japan
E.D. Specht
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831
P. Zschack
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831
G. E. Ice
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831
K. Hisatsune
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 Nagasaki University, Sakamoto-machi, Nagasaki 852, Japan
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Abstract

X-ray scattering data obtained for multiple wavelengths with synchrotron radiation were analyzed by the Rietveld method to determine Ni and Pd distributions on the Cu(000) and Au(½½½) sites in the CuAuI tetragonal P4/mmm structure. Alloys of CuAuxM1-x containing 6 at. % Ni or 10 and 25 at. % Pd were processed to obtain maximum ordering. Nickel is predominantly found on the Cu site and most all the Pd is found on the Au site. The uncertainty in site occupation parameters is discussed for various contributions which affect powder intensity measurements. For highly absorbing materials, an observed powder roughness effect decreases the low angle (2θ) intensities relative to the high 2θ intensities. This effect reduces the reliability of the thermal parameters and obscures a proper description of the thermal motion of the two sublattices. Corrections to the X-ray intensity data for surface roughness/porosity effects reduce uncertainties to about ±1 at. % on the refined value of the site occupations. This use of variable wavelength X-rays with simultaneous refinement of the corresponding data is capable of distinguishing site occupations even between two elements of almost equal scattering factor as, for example, Cu and Ni atoms in this investigation. Chemical phase stability is related to the site occupation parameters.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 369
Copyright
Copyright © Materials Research Society 1991

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References

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