Dear Mario,
If the quantity of FeCO3 appears to be smaller than the actual value, then it
could be due to absorption. If you are using a copper source (CuKalpha) then
that excites iron fluorescence, which is radiated equally in all directions...
this means that the beam does not penetrate the FeCO3 particles entirely, and
results in incomplete diffraction from these particles.
There are programs that correct for this problem, but as far as I know there is
no freeware to deal with this effect.
- Kurt
*********
Kurt Leinenweber
Dept. of Chemistry and Biochemistry
Arizona State University
Tempe, AZ 85287-1604
phone (480)-965-8853
fax (480)-965-2747
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-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Monday, October 27, 2008 8:48 AM
To: Rietveld_l@ill.fr
Subject: Quantitative analysis
Dear all,
I have this question,
I have been refined one mixture (of well-know percentage composition) of
CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation in CaCO3 (104)
and CaF2 (111) with good results. When I add to the mixture FeCO3 and I
refine with preferential orientation (104), it happens that when I don´t
apply the preferential orientation in all this phases, I have correct
values of percentage composition, but when I apply the preferential
orientation the refinement is good but with incorrect values of percentage
composition. This experiment has been taken in Bragg Brentano geometry.
How I should refine this mixture?
Thanks a lot by your help.
Mario Macías
Universidad Industrial de Santander
Colombia
