I am attempting to perform XRD analysis on the 21R Sialon polytype, by seeing how much aluminium nitride is within each sample. Although, I cannot perform Rietveld refinements on this as I have no XRD data for pure 21R. I have been unable to find any data through research.
What data do I need to perform this task, and is it possible to perform Rietveld calculations if it does not exist within my Match database.
I am using Match! to attempt to perform these calculations.
Article 21R-Sialon ceramics, obtained by hot pressing
Article A porous (La, Sm) co-doped Sialon-polytypoid ceramic with co...
Hi Luke,
These two papers state that a reference diffraction pattern for the 21R polytype can be found in JSPDS-53-1012. JSPDS is a data-base from the International Centre of Diffraction Data (ICDD) https://www.icdd.com/ and -53-1012 is the reference number of the pattern. As far as I know, you have to pay to access to this data-base, and unfortunately, I don't have access to it, so I can't help you out.
What you could do is contact the authors of any of the two papers I stated above and ask them to send you the JSPDS-53-1012 pattern that you could compare with your diffraction pattern. I am not familiar at all with the system you are studying but in the Huang paper I have linked to they state:
The disordered structure is common in the polytypoid phases because of the intergrowth that involves different numbers of structural blocks.6 It is difficult to prepare single crystals or powders with ordered structure (i.e. without intergrowth
). As a consequence, no crystal data is currently available in the Inorganic Crystal Structure Database (ICSD) for Sialon polytypoids.
This was in 2013 and I have no idea if the crystal structure was determined in the meantime. However, if the crystal structure is not known you cannot perform a Rietveld refinement of your data. If you would want to solve the crystal structure, you would either have to grow a single crystal, or try solving the structure from powder data using a software such as Expo2014 or FOX, but first you would also have to index the unit-cell... That said solving a structure from powder data is a rather difficult task and unfortunately still often unsuccessful (and even more so since your system appears to be discorded).
HTH,
Johannes
Johannes M. Meusburger
Hi Johannes,
Thankyou for pointing me in the right direction. It seems as though there is no crystal data for the 21R polytype.
Regards,
Luke
Hi Luke Forster,
Also since you have mentioned that you are just interested to find out what the phase fractions for the 21R polytype and the aluminium nitride are, I wanted to ask if you know the precise chemical formula of both phases? If yes, all you would have to do is perform a bulk chemical analysis (ICPMS, XRF, whatever) and you should easily be able to calculate the phase fraction.
HTH,
Johannes
Johannes M. Meusburger
Yes I do, although onsite we do not have access too MS or XRF equipment, just XRD analysis. Appreciate the help!
Regards,
Luke
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