Hello, I am trying to do a very simple phase fraction quantification(many phases in my powder), a professor suggested just do a very simple quantification of (unit cell concentration of phase A)/(unit cell concentration of phase B) = Intensity of peak belong to A / Intensity of peak belong to B with consideration of multiplicity. Which we are assuming Polarization, absorption, and temperature effect do not impact XRD intensity too much, how much of this is true, also what's your overall view on this estimation?
Dear Shengquan Xuan ,
We have several methods to quantify the phase fraction in a sample. The Reference intensity ratio (RIR) is the method that your professor suggested. First, you have to scale all XRD experiments in basis of a known reference used for XRD experiment, sometimes it is just NaCl. However, even if you assume that all parameters are constant, you need information like density of the phases, linear attenuation coefficient, and structure factor constant. It is not quite simple and in my opinion do not give reliable results.
This material can help you with the RIR method:
https://www.icdd.com/assets/tutorials/Quantitative-Analysis-RIR.pdf
I strongly recommend you to use Rietveld refinement method. You have free software like GSAS/EXPGUI, GSAS II, or Fullprof.
the effects you cite depend on the kind of phases which constitute your mixture, the absorption coefficient could be very different between the phases so the quantitative analysis could be wrong. These methods are affected by errors. If you use a Rietveld refinement program you can take into account all these parameters in the same program and the quantitative analysis is more accurate
RIR is a old technique moreover you need the standard sample also. Rietveld refinement technique using GSAS, GSAS II or Fullprof may accurate phase fraction. But one has to be careful while refining the phase fraction otherwise it will lead to erroneous results.
Gustavo Henrique de Magalhães Gomes This is great information, Thank you! We have paid software to do Rietveld refinement, but the material I am working with has close to no CIF file available in the literature. And especially, there is no RIR value regarding the phase, RIR is required to do Rietveld refinement correct?
Shengquan Xuan you are welcome.
Which is your material?
I am used to employ GSAS/EXPGUI for Rietveld refinement. For this, you have to supply the .CIF files from all phases that you have in your sample. A XY notepad file with your XRD intensity, and a .prm file that contains the equipment values of broadening, equipment zero, and moreover (not needed in most cases, you can use a dummy .prm file - blank file).
You don't need RiR values for refinement, just the mentioned above using GSAS/EXPGUI. The same accounts for GSAS II. For FullProf, I do not have expertise.
Best regards,
Gustavo.
Gustavo Henrique de Magalhães Gomes I work with Hydromagnesite, Dypingite, and Nesquehonite. Hydromagnesite and Nesquehonite's CIF files I have downloaded from ICSD, and interestingly, I cannot do quantitative analysis with these CIFs without RIR values(the software cannot output phase fraction after the refinement). And Dypingite is the one I cannot get any CIF from any database.
Thank you Gustavo,
Marcella Bini Thank you for your input! do you have any idea how much of these factors(Polarization, absorption, and temperature) can influence the intensity? especially for inorganic materials?
Severe complication. The crystal structure of dypingite is not sufficiently known (it is monoclinic, but the group and position of atoms are unknown), so the cif file does not exist. As for the original question, linear absorption coefficients have the greatest influence on the intensities in mixtures. Parameters describing possible texturing are also important. I remember, for example, the case (mixture of 50/50% wt. Quartz + calcite), when due to differences in absorption coefficients and calcite texturation, the result visually corresponds to about 2/1.
Nothing is complicated. First try to do find out the compositions of the phases A and B. Once the phases are identified try to find out the standard XRD pattern from the ICDD database using the MATCH software and try to make the CIF file for both the phases and now you can do the Rietveld refinement and it will take care of temperature effect through thermal parameters. Of course polarization and absorption effects also will be taken care in the refinement.
Thank you Dalibor Matýsek and Dharmadoss Sornadurai for great insights, Dalibor Matýsek, is Dypingite a prominent material/mineral? is there a reason why this phase is hardly studied?
What do I know about dypingite? It is a fairly rare mineral found in hydrothermally altered serpentinites. It was described in 1970 from Dypingdal, Snarum region in Norway. It is one of a number of hydrated Mg hydroxycarbonates that are quite difficult to identify and may be less stable. A significant complication and reason for the low research will be that there are probably no crystals at all, measurable by XRD on a single crystal. Solving the structure by powder diffraction would probably require sychrotron diffraction.
However, from a good powder diffraction pattern, one could probably at least find out the space group and cell parameters.
Some reading about dypingite:
https://rruff.info/doclib/MinMag/Volume_48/48-348-437.pdf
Please check the fully-ready preprint article DOI: 10.13140/RG.2.2.27720.65287/3, Title: Qualitative Analyses of Thin Film-Based Materials Validating New Structures of Atoms
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