ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
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 Al2O3 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 2θ = 30°, falling to 2 × 10−4 at 2θ = 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 CeO2, Al2O3 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889884011043
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