Probably the best approach is to include a known quantity of an internal
standard in the sample. Sample preparation is very important and you
will have to make sure the standard is carefully weighed and that the
mixiing procedure that is used is efficient. You can then carry out
quantitative Rietveld refinement on the sample using a programme capable
of this.
After refinement, the rietveld programme should give a weight percent
value for the internal standard higher than the actual quantity that is
present (assuming there is an amorphous phase). The quantity of
amorphous material can be calculated using the equation
wa = 100* (1- (a/m))
where wa = weight% of amorphous material
a = actual weight% of internal standard
m = weight% of internal standard supplied by the Rietveld
programme
The quantities of crystalline phases can be calculated using the
equation:
wcn = (a/m) * mcn
where wcn = weight percent of crystalline phase n
mcn = weight% of crystalline phase n supplied by the
Rietveld programme.
You will then obviously have to correct your final values to take into
account the fact that the internal standard was not in the original
sample.
Regards,
Tom Dyer
Division of Civil Engineering
University of Dundee
