Please prepare for a shameless plug for the newly certified NIST SRM 676a:
In order to measure amorphous content (via non-PDF diffraction methods) one needs two things: 1) An unbiased diffraction method for measurement of phase abundance (laughter please) and 2) A standard of known phase purity. A quantitative Rietveld analysis of data from a divergent beam powder diffractometer yields results that are consistently biased by a few percent. The nature of the bias appears dependent on the phases being measured and I don't really know of the origin. But by process of elimination, I think it is due to an over simplistic model for the Lorentz/polarization factor. Therefore, you are better off using nonconventional sources, or accepting that your results may be inaccurate to a few percent. For 10+ years I/we have been pursuing an experimental design to measure absolute phase purity. It has taken several iterations to obtain results I/we cared to talk about. SRM 676 was recertified ~2 years ago for phase purity, however, stocks of it were exhausted (the recertification is retroactive). SRM 676a was released for sale a week or two ago and offers improvements in both the phase purity (99%) and the error bounds on the certified value.
See: https://srmors.nist.gov/view_detail.cfm?srm=676A
I haven't written the work up yet (I'm working on it); but the experimental design is described in the certificate.
Regards,
Jim
At 06:58 AM 2/27/2008, you wrote:
Dear Users,
I'm trying to determine the percentage crystallinity in a crystalline/amorphous mixture, could someone point me in a foolproof direction.
Thanks,
John
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