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The influence of surface roughness on diffracted X-ray intensities in Bragg–Brentano geometry and its effect on the structure determination by means of Rietveld analysis

Published online by Cambridge University Press:  10 January 2013

W. Pitschke ,
H. Hermann  and
N. Mattern
W. Pitschke
Affiliation:
Institut für Festkörper- und Werkstofforschung Dresden Helmholtzstraße 20, D-0-8027 Dresden, Germany
H. Hermann
Affiliation:
Institut für Festkörper- und Werkstofforschung Dresden Helmholtzstraße 20, D-0-8027 Dresden, Germany
N. Mattern
Affiliation:
Institut für Festkörper- und Werkstofforschung Dresden Helmholtzstraße 20, D-0-8027 Dresden, Germany
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Abstract

Measurements of X-ray diffraction patterns of high-Tc superconductor and tungsten–carbide powder samples using a Bragg–Brentano diffractometer showed systematic variations of the intensities for different preparation conditions. For specimens with high surface roughness, an angle-dependent decrease of the intensities is observed which is caused by the microabsorption of the X-rays due to the microstructure of the powder sample. In Rietveld analysis, the thermal parameters are strongly influenced by this effect and may tend to negative values. A realistic description of the surface structure of flat powder samples is proposed. Using an analytical approximation for the microabsorption effect and its dependence on the microstructural parameters the Rietveld refinement yields reasonable values for the thermal parameters.

Type
Research Article
Information
Powder Diffraction , Volume 8 , Issue 2 , June 1993 , pp. 74 - 83
Copyright
Copyright © Cambridge University Press 1993

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