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

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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;
Title: Size-Strain Line-Broadening Analysis of the Ceria Round-Robin Sample
Published: December 01, 2004
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
Pages: pp. 1 - 14
Keywords: line broadening;Rietveld refinement;size-strain separation;Warren-Averbach analysis
Research Areas: Materials Science
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