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An Analysis of the Effect of Different Instrumental Conditions on the Shapes of X-ray Powder Line Profiles

Published online by Cambridge University Press:  06 March 2019

R. W. Cheary  and
J. P. Cline
R. W. Cheary
Affiliation:
Department of Applied Physics, University of Technology, Sydney PO. Box 123, BroadwayNSW 2007, Australia
J. P. Cline
Affiliation:
Ceramics Division, National Institute of Standards and Technology Gaithersburg, MD 20899 USA
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Abstract

In this investigation we have examined how the full width at half maximum intensity (FWHM) and asymmetry of x-ray powder diffraction line profiles are influenced by the instrumental conditions adopted. Experimental x-ray data has been collected for a matrix of instrumental conditions by systematically varying the divergence slit angle (and the corresponding anti-scatter slit) over the range 0.25° to 1.25°, by using either a 0.05mm or 0.2mm receiving slit, or by removing the diffracted beam Soller slit. The line profile Standard Reference Material, SRM, 660 (LaB6) was used as the powder specimen in that it imparts minimal specimen induced broadening to the diffraction profiles. X-ray data were collected on a conventional, divergent beam, x-ray diffractometer using CuKα radiation.

The FWHM of the CuKα1 component can be as low as 0.035°2θ for high resolution conditions, but is normally ∼0.1°2θ at 2θ ≈ 30° for the instrumental conditions adopted in routine diffractometry. Below 2θ = 50°, the divergence slit has a significant effect on the FWHM and is the major cause of the increase in FWHM with decreasing 2θ. Results are presented of the 2θ dependence of FWHM values for each of the instrumental conditions recorded. A general relationship for the 2θ dependence of the FWHM and the asymmetry has been investigated to supersede the inappropriate Cagliotti expression frequently used in x-ray Rietvcld refinement.

Type
II. Phase Analysis, Accuracy and Standards in Powder Diffraction
Information
Advances in X-Ray Analysis , Volume 38: Forty-third Annual Conference on Applications of X-ray Analysis , 1994 , pp. 75 - 82
Copyright
Copyright © International Centre for Diffraction Data 1994

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