Alice Courleux
Fri, 19 Feb 2010 05:34:33 -0800
Dear Rietvelders,I am using Fullprof to microstructural analysis of particles. I have one type of particle but different sample with different sizes (particles increase after heat treatment). Their crystallites size fluctuates between 10nm and 1µm. I know that 1µm is big for a refinement Rietveld. To calculate the size, I refine Y (Lorentzian componant) then Ig (Gauss component). If the crystallites are small (<20nm) I can only refine the Y parameter. If I try to refine Ig, I have a error message "negative Gaussian parameter" and no crystallites size. For bigger crystallites, I can refine Y and Ig. If I only refine Y, the crystallite size is smaller than the size with Y and Ig refinement. For the biggest crystallites if I only refine Y parameter the size is "99999nm". However if I refine Ig parameter too, I succeed to have a size (1300nm for example)... I don't understand why I can't refine Ig whatever the crystallites size... Is ther any reason to that? Should I only refine Y for all my samples? Or refine Y and Ig when it's work and only Y when Ig bugs?
Have you ever seen this problem? Thanks a lot for your help. Best regards, Alice -- Laboratoire des Multimatériaux et Interfaces - CNRS UMR 5615 Université Claude Bernard Lyon 1 3ème étage - Bâtiment Berthollet 43, boulevard du 11 Novembre 1918 69622 VILLEURBANNE Cedex Mail: alice.courl...@univ-lyon1.fr Tél: 04.72.43.12.34