Julian has pointed to an important issue, the particle size in the
mixtures. Even when mue of the standard and sample material are in the
same magnitude, and even when the particles sizes of both powders
powders are known and acceptable small with respect to microabsorbtion,
absorbtion contrast
Is it really amorphous content, or is there a whole bunch of very fine
nanocrystalline stuff or material with a very high defect density that is
widening the peak? If the fitter is having trouble matching the peak shape, it
may be ascribing a fairly arbitrary portion between amorphous and cryst
Thinking a little outside of the crystallographic aspects, do you have element
analysis data? Either XRF or ICP-MS would give a good guide to the sample
composition, and it should match to the composition you are using in the
structure model.
I find it is worth drying both the sample and spike
> But with some electronic transmission analysis no amorphous is observed.
Could the TEM investigation have led to recrystallisation?
Have you tried polarised-light microscopy to check the character of the
amorphous phase?
Cheers, Uwe
-Ursprüngliche Nachricht-
Von: rietveld_l-requ...@i
Dear François,
Maybe you have a strongly disordered system. Depending on the type of disorder
and the distribution of diffuse intensity, it can also have an influence on the
reflection profile (thermal diffuse scattering).
Michael
Dr. Michael Wörle
Head Small Molecule Crystallography Center
Lab
It would be useful to have more details. Certain types of materials may be
tricky to refine if your measurement range extends beyond where you can
visibly see distinct peaks. At higher angles you might have a majority of
low intensity overlapping peaks (exacerbated by the addition of an internal
st
Dear François,
I can think of no reason for a correlation between your peak shape and your
resultant amorphous content, unless somehow the super-Lorentzian peak shape is
not providing accurate intensities. Have you tried your fit with another peak
shape or a fundamental parameters approach? I a
Dear François,
I've to admit that I am no expert on the quantitative phase analysis. If
the analysis suggest 40% amorphous compound, I'd expect that should be
clearly visible in the diffraction pattern as a fairly strong, broad
maximum with a FWHM of some 7 to 10° (CuKalpha). If you do not see
Dear Rietveld users,
I have some industrial compound presenting a strong hyper-Lorentzian peak shape
(eta=1.1 with HighScore). When we calculate the amorphous content after an
internal standard addition, the result is 40%. The micro-absorption effect has
been minimized (mu of the internal stan
