This is a can of worms that keeps cropping up now and again.  Rather than go 
into masses of detail I'd suggest looking at the Rietveld mailing list archive 
for some fairly detailed discussions on the subject.  I'd go with Bob's route 
as it's applicable in a laboratory environment but foolproof it isn't and good 
sample preparation is vital.
 
Pam

________________________________

From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED]
Sent: Wed 27/02/2008 11:52 AM
To: rietveld_l@ill.fr
Subject: RE: % Crystallinity



John (& others),
The best way to determine %crystallinity (or %amorphous) is to do "spiking" 
experiments with material with known (preferably ~100%) crystallinity. The 
change in the apparent phase fractions by Bragg intensities as compared to that 
expected from the masses can be used to estimate the fraction that doesn't 
Bragg scatter (i.e. the amorphous content). The spiking material should also be 
chosen to have nearly matching absorption to avoid systematic effects (e.g. 
Brindley corrections). It does not have to be the same phase as the crystalline 
phase in your sample. There are literature references to this but I can't 
recall the exact ones to look at. Perhaps others might know them better. (BTW - 
this is not a PDF problem).
Bob Von Dreele

________________________________

From: john o callaghan [mailto:[EMAIL PROTECTED]
Sent: Wed 2/27/2008 5:58 AM
To: rietveld_l@ill.fr
Subject: % Crystallinity


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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