annakater
Dear Topas users,
I am trying to quantify the amorphous component in some patterns. I would like to avoid the addition method, so my plan was to use a "peak phase" to model the amorphous compound. I have a good determination of the background, so background-peak correlations should not be a problem. Would this make any sense? The main problem is of course that there is no scale factor for a peak phase, so the quantification should be based on another parameter. Any suggestions on how to solve this? Provided that the whole venture actually makes sense.
I saw Brucker is launching an addition to TOPAS, called PONKCS, advertising exactly this function - so I suppose there is more people out there that would preferably avoid spiking.
nvyscarlett
The original paper detailing the PONKCS method is Scarlett & Madsen, (2006) Powder Diffraction 21 (4). It details how to derive the calibration factor for quantification of an amorphous/unknown sample which is equivalent to the "ZMV" value for a known crystal structure. It requires though, that you have a sample which can be used for this calibration, i.e. a pure sample of the unknown or one in which its weight fraction is known. The peak phase you have fitted can be scaled as a fixed group and the resulting scale factor then used in the usual Hill/Howard QPA determination.
This methodology, including walk-throughs, has been presented at several TOPAS workshops and the material may be available via Bruker. Btw if you are in Australia there is a TOPAS workshop in Sydney next weekend where it will get another outing!
Good luck.
annakater
That is a nice and comprehensive paper, but I am not sure if the method is directly applicable for amorphous phases?
I have calculated density on the samples and the crystalline phases have been well determined, but it would not make any sense to try and calculate a unit cell volume for an amorphous component.
Unfortunately (or fortunately, considering the current weather conditions) i'm not in Australia, but thanks for the tip!
iangie
Ross Williams use PONKCS method succesfully quant two kinds of amorphous material. Paper available soon in Journal of American Ceramic Society. "Quantification of the extent of reaction of matakaoline based geopolymers using XRD, SEM and EDS"