Want to use an internal standard for XRD quantification (amorphous phase quantification). I have read that corundum is the best internal standard for such an analysis and I am wondering to know why?! What makes corundum the best? I mean why can't I use NaCl as an internal standard (or something else)?
Your help is much appreciated!
For a generally applicable standard you want a compound that is (a) very chemically inert, including little to no tendency for hydration; (b) has very little (ideally zero) stoichiometric variability; (c) typically available powder has low aspect ratio (i.e. platelets or needle-like crystals are not desirable) to avoid texturing. Corundum is nearly ideal on all 3 counts. You also want a decent diffraction intensity; in this corundum is better than diamond, which otherwise would be a fine candidate.
Quartz is also extensively used as an internal standard. The values for 2 theta are well-known and it can be used to correct for instrumental broadening in the case of using the Scherrer equation in XRD line broadening.
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