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Size-Strain Line-Broadening Analysis of the Ceria Round-Robin Sample

Published

Author(s)

Davor Balzar, N Audebrand, M R. Daymond, A Fitch, A Hewat, J I. Langford, A Le Bail, D Louer, P Masson, Christopher N. McCowan, N Popa, P W. Stephens, B H. Toby

Abstract

We report the results of a line-broadening study on a ceria sample prepared for a size-strain round robin. The sample was prepared from a recursor hydrated ceria by heating in a silica crucible at 650 C for 45 hours. Another ceria sample wasprepared to correct for the effects of instrumental broadening by annealing commercially obtained ceria at 1300 C for 3 h and slowly cooling it in the furnace. The diffraction measurements were carried out on two laboratory and two synchrotron x-ray sources, two constant-wavelength neutron and a TOF neutron source. SEM micrographs have shown predominantly spherical grain shape with a lognormal size distribution. Diffraction measurements were analyzed by three methods: the model assuming a lognormal size distribution of spherical crystallites, Warren-Averbach analysis, and Rietveld refinement. The last two methodshave detected a relatively small strain in the sample, as opposed to the first method. Assuming a strain-free sample, the results from all three methods agree well. The average real crystallite size, on the assumption of a spherical crystallite shape, is about 180 A. The scatter of results given by different instruments is relatively small, although significantly larger than estimated standard uncertainties. The Rietveld-refinement results for this ceria sample indicate that the diffraction peaks can be successfully approximated with a pseudo-Voigt function. In a common approximation used in Rietveld-refinement programs, this implies that the size-broadened profile has to be a Voigt or pseudo-Voigt function with a significant Gaussian component.
Citation
Journal of Applied Crystallography
Volume
37
Issue
Part 6

Keywords

line broadening, Rietveld refinement, size-strain separation, Warren-Averbach analysis

Citation

Balzar, D. , Audebrand, N. , Daymond, M. , Fitch, A. , Hewat, A. , Langford, J. , Le, A. , Louer, D. , Masson, P. , McCowan, C. , Popa, N. , Stephens, P. and Toby, B. (2004), Size-Strain Line-Broadening Analysis of the Ceria Round-Robin Sample, Journal of Applied Crystallography, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851306 (Accessed April 12, 2024)
Created December 1, 2004, Updated February 19, 2017