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Synchrotron X‐ray powder diffraction
Author(s) -
Hastings J. B.,
Thomlinson W.,
Cox D. E.
Publication year - 1984
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889884011043
Subject(s) - monochromator , synchrotron , synchrotron radiation , diffraction , resolution (logic) , powder diffraction , mosaicity , optics , x ray , materials science , x ray crystallography , wavelength , physics , crystallography , chemistry , artificial intelligence , computer science
The application of synchrotron X‐ray radiation to powder diffraction is described. A perfect Si double‐crystal monochromator at the Cornell High Energy Synchrotron Source (CHESS) was used in conjunction with Si, Ge, LiF and Al 2 O 3 analyzers to investigate resolution and intensity characteristics at selected wavelengths between 1.07 and 1.54 Å. The results obtained with Ge at 1.54 Å gave a resolution Δd/d of 5 × 10 −4 at 2 θ = 30°, falling to 2 × 10 −4 at 2 θ = 140°. Analysis of the peak shapes is described in detail, with particular emphasis on the asymmetry observed at angles below 50° due to axial divergence effects. With a simple correction to allow for these, the peak shapes are found to be well represented by a convolution of Gaussian and Lorentzian components, the respective peak widths of these being related to the intrinsic resolution and sample broadening effects. It is pointed out that the use of a crystal analyzer should eliminate shifts in the Bragg‐peak positions owing to the displacement‐type aberrations which occur with conventional focusing‐type diffractometers. Except for a constant zero error, the mean discrepancy in observed and calculated peak positions between 0 and 90° for reference samples CeO 2 , Al 2 O 3 and NiO is found to be only about 0.003°. Finally, some general remarks are made about the application of the Rietveld profile technique to structural analysis from synchrotron powder diffraction data.