I have an XRD result of my samples, I would like to know how to calculate the amount of amorphous phase?
Hello,
Quantification of PXRD is quite a complex issue and quantification of amorphous impurities is particularly complicated. There are a number of methodologies, but all are based on the addition of a known amount of internal standard. Probably the most serious approach is to combination the internal standard method with the Rietveld method. However, the Rietveld method requires knowledge of the crystal structures of all crystalline phases.
We do not know anything about the nature of the sample, so it is not possible to design a quantification procedure.
PXRD/or XRPD is not the best technique to calculate the amount of amorphous phase, although it is a 'golden' rule to experimentally define crystalline materials from amorphous. If you just need to know a 'dirty' estimation, you can characterize your materials according to the FWHM of different peaks and particularly the baseline of an overall diffraction peaks pattern.
An amorphous solid is characterized by an almost complete lack of periodicity revealed by a broad maxima in the x-ray spectrum. To get a rough idea, take a look the ratio of area under the broad maxima to the area under the intensity of diffracted peaks.
Dear Angelica Cardoza ,
Elif Tarhan Bor is very close close to the answer.
Commonly the amount of crystallinity is calculated by the ratio Ic/(Ic+Ia) with Ic as the integral of the 'crystalline' peaks and Ia as the integral of the amorphous peaks. One may multiply by 100 to have the % crystallinity.
The amount of amorphous phase is accordingly Ia/(Ic +Ia).
Please see for example the answers of:
https://www.researchgate.net/post/How-to-calculate-the-percentage-crystallinity-from-XRD-plot-using-origin-software
However, it is often not simple to identify the amorphous part Ia, especially in the presence of a background and a lot of closely arranged crystalline peaks.
Thus I must recommend the answer of Dalibor Matýsek to have careful look on your sample system and the crystal structure of the crystalline phase(s).
Best regards
G.M.
Hello, if it could be of your interest, I introduce you which, in my opinion, is the most adequate technique in this regard. In my investigation, I have successfully applied Rietveld refinement using controlled proportions of high cristalline Al2O3 as a standard. It is very useful to quantitatively determine both cristalline and amorphous phase. You can take a look at some of my publications where we applied this technique. Best regards.
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