The overestimation of the corundum concentration by QPA will give you the amorphous concentration as follows:
Amorphous= (QPA amount - actual amount) / (QPA amount *(1-actual amount)) Then you correct all QPA concentrations with the equation actual amount = (1-amorphous) * QPA amount (that is, if you want to exclude corundum as internal standard and get the relative concentrations of the remaining crystalline phases and the amorphous) I believe a good reference for this and the overall discussion is 'Rietveld quantitative amorphous content analysis', A,G. De La Torre, S. Bruque, M.A. Aranda. Journal of applied crystallography, 2001 Maria Chrysochoou Assistant Professor Department of Civil and Environmental Engineering University of Connecticut Storrs CT 06269 E-Mail: [EMAIL PROTECTED] Tel.: (860) 486 3594 Fax: (860) 486 2298 -----Original Message----- From: Lee Gerrard [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 14, 2008 8:21 AM To: rietveld_l@ill.fr Subject: Question on QPA - Amorphous/crystalline mix I have a question for the list as I know there are a number of people working on QPA. Ok the question is as follows:- We have a mixture of a number of crystalline phases (A and B) and an amorphous (glassy) phase. We can do Rietveld refinement on this and get weight percentage (wt.%) values for the crystalline components. We have added a known amount of corundum as a standard and refined again. Example values we get are as follows:- Phase A 10 wt.% Phase B 50 wt.% Corundum 40 wt.% BUT we know we have added only 33 wt.% corundum - are we able to calculate the wt.% of the amorphous content from the known values? I have tried scaling/ratio'ing the values to the known corundum amount therefore giving:- Phase A 8.25 % Phase B 41.25 % Corundum 33 % TOTAL 82.5 % which leaves 17.5 % left over. Hence must be the amorphous part?? I am not totally convinced by this method at all and would love to know how is best to go about solving this problem. Many thanks, Lee ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dr. Lee A. Gerrard BSc CChem CSci MRSC Materials Scientist Materials Science Research Division SB40.1 AWE Plc Aldermaston, Reading, Berkshire RG7 4PR Tel: +44 (0)118 982 6516 Fax: +44 (0)118 982 4739 Email: [EMAIL PROTECTED] ~~~~~~~~~~~~~~~~~~~~~~~~~~~
