I am trying to synthesize a crystalline inorganic compound with a very low tendency of devitrification. A posteriori, XRD patterns reveal the presence of a non-negligible amount of amorphous material through the crystalline matrix. So, how can I practically determine the amount/percentage of this amorphous phase?
Hi Mohammed
In the following article you will find how to do it using XRD:
Determination of crystallinity in crystallized glasses by X-ray diffraction Original Research Article
Journal of Non-Crystalline Solids, Volume 21, Issue 1, June 1976, Pages 125-136
L. Červinka, J. Dusil
If fraction of amorphous phase is low (below 30%) thermal conductivity measurement will help to estimate percentage. Just assume thermal conductivity of amorphous phase 0 and you get an upper volume fraction limit. Of course, you will need a reference 100% crystalline material to compare.
Hi Mohammed
In the following article you will find how to do it using XRD:
Determination of crystallinity in crystallized glasses by X-ray diffraction Original Research Article
Journal of Non-Crystalline Solids, Volume 21, Issue 1, June 1976, Pages 125-136
L. Červinka, J. Dusil
Hello Mohammad,
For the X-ray diffraction patterns, you need a calibration curve. Again, it is not very precise if the quantity of the amorphous phase is low.
Differential Scanning Calorimetry can help you quantifying the amorphous phase very precisely.
% of Crystallinity is a relative term. There is no compound ideally known to be 100 % crystalline. To know the highest crystalline compound, it is possible from the sum of prominent XRD or FT-IR peaks at standard conditions. Another method, if the compound is porous, based on its N2 or model compound- adsorption one can find out the most crystalline compound. In computer modelling, one can find out the maximum possible adsorption of a particular compound over the solid.
A relative common practice is to assume the diffraction pattern of your material to be the sum of various gaussian curves, both sharp and broad in form, all convoluted in the finall pattern. You need to perform a deconvolution of this curves, so that you can determine the areas of each individual gaussian. The broader curves are related to amorphous regions; the sharper ones to crystalline planes. The crystallinity index is just the sum of the areas of the sharp curves over the sum of the areas of both sharp and broad curves.
This method is known as Ruland's Method and, although prone to operatorwise experimental error, is a rapid and relatively simple way to gauge the amount of crystalline and/or amorphous phases present in a semicrystalline material.
Regards.
Thank you so much for your precious help and for sharing your knowledge around the different existing techniques!
You can use spiking method and quantify the amorphous content using rietveld refinement.
@Anup Can you please provide further information about this method of quantification.
Thank you in advance.
add known amount of any crystalline phase(spiked phase)(which is not present in your sample) into your sample, mix well and get the XRD pattern. Quantify it using Rietveld refinement (there are several softwares for Rietveld).
if your sample contains any amorphous phase then you will get overestimation of your spiked phase. then using simple arithmetic you can quantify the amorphous content.
you can find plenty of literatures on this spiking method, just google it!!
I have the same problem. Can someone send me the paper "Determination of crystallinity in crystallized glasses by X-ray diffraction"?
anyway, you can use the Rietveld method and an internal standard, such as rutile or corundum. My experience is with GSAS-EXPGUI software package. Regards
Next to spiking (Internal standard method) you can also use an external standard (K-Factor method) to determine the amorphous percentage from an XRPD pattern The original publication about this method is:
B.H. O’Connor & M.D. Raven, Application of the Rietveld Refinement Procedure in Assaying Powdered Mixtures, Powder Diffraction (1988), 3, 2–6.
Here is a short overview how it works:
Conference Paper RIETVELD AMORPHOUS QUANTIFICATION WITHOUT PAIN: THE K-FACTOR APPROACH
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering