Can XRD-Rietveld analysis provide components / phases present in the amorphous phase the same way it does for crystalline material? Are there other methods available?
Dear Katrina Skerratt-Love ,
the evaluation of XRD pattern of amorphous material is a challenge because it mainly consist of a large broad hump which some times is more or less structured by one or two shoulders. From that perspective you already see, that there is much less information available compared to a 'crystalline' XRD pattern.
In order to compensate the lack of information a bit, one uses the small angle x-ray scattering (SAXS) technique, the experimental set up of which is in principle similar to an XRD one. The difference is the used range of a specal physical quantity known as the magnitude of the momonetum transfer vector q*), which is a parameter that involves the theta scale of the goniometer and the wavelength lambda in use.
Details about this and the evaluation procedure of such 'amorphous' pattern you will find for example in:
https://www-ssrl.slac.stanford.edu/conferences/workshops/scatter2006/talks/hufnagel.pdf
The outcome of such an evaluation is the pairdistribution function of the atoms in the amorphous sample;
Tutorial on pairdistribution function:
https://www.youtube.com/watch?v=NyAG_MU3jJs
I admit, that it is a hard job to dive deeper into this subject...
*) q = (4*pi/lamda)*sin(theta);
when applying the Bragg Law (lambda =2*dhkl*sin(theta)), you get
q = 2*pi/dhkl, that means: in q space the diffraction peaks and humps show up at well defined positions, which are not dependent on the wavelength as in the theta/2theta representation...
Good luck and
best regards
G.M.
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