Nelson (and others) The Scherrer equation is a quick and easy method to get a feel for relative sizes for data from the same instrument and is still a useful tool in that regard. However, beware of relying on absolute values from the Scherrer equation in work to be submitted for peer review. Depending on the referee you could be given a very hard time for not using something more rigorous - quite a bit of work has been done since Scherrer's paper in 1918. Look into the background and assumptions alluded to by Jeff more closely and you'll find out why I for one would be one of those 'awkward' referees.
Best regards Pam From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Nicolich, Jeffrey Sent: Tuesday, 07 January, 2014 11:15 AM To: Nelson; rietveld_l@ill.fr Subject: RE: limitation sherrer formula Nelson, There is no upper limit on particle size. The crystallite size limit depends only on your ability to measure a meaningful difference in line broadening between your sample and your instrument standard (e.g. LaB6, NIST SRM 660). A well aligned K-alpha1 machine can get you close to 1 micron (at least theoretically), but for a typical laboratory instrument ~200 nm is very reasonable. You can simply plug in some example numbers into the Scherrer formula to understand why this is. Keep in mind the Scherrer equation is only an approximation based on many assumptions. While there are more sophisticated x-ray methods available, they all have in common a larger error at larger crystallite size numbers. Perhaps light-scattering, image analysis or some other alternative technique would be more appropriate for your application? Best regards, Jeff Jeffrey Nicolich | Sr. Analytical Chemist W. R. Grace & Co., 62 Whittemore Ave, Cambridge, MA 02140, USA | T +1 617.498.3816 | F +1 617.498.4360 | jeffrey.nicol...@grace.com<mailto:jeffrey.nicol...@grace.com> ________________________________ THIS EMAIL AND ANY ATTACHED FILES ARE CONFIDENTIAL AND MAY BE LEGALLY PRIVILEGED. If you are not the addressee, any disclosure, reproduction, copying, distribution, or use of this communication is strictly prohibited. If you have received this transmission in error please notify the sender immediately and then delete this email. From: rietveld_l-requ...@ill.fr<mailto:rietveld_l-requ...@ill.fr> [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Nelson Sent: Tuesday, January 07, 2014 10:28 AM To: rietveld_l@ill.fr<mailto:rietveld_l@ill.fr> Subject: limitation sherrer formula Dear Rietvelds The Scherrer formula is only applicable if the particle size is ~ 200 nm or less - it makes use of the line width due to the limited distance range ? This is true ? Wich paper are recomended to know why ? Best regards
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