RE: High temperature PXRD fitting in TOPAS
Assuming that your sample is stable over the temperature range, then the temperature will only affect the cell paramaters. (and maybe crystallite size) Allowing them to refine should be enough to allow for good fits. Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] _ From: sisir ray [mailto:[EMAIL PROTECTED] Sent: Friday, 16 November 2007 12:22 To: rietveld_l@ill.fr Subject: High temperature PXRD fitting in TOPAS Hi, I have got high temperature Powder xrd data (from lab xray source) in the range of 30 ~1000 C . But i am not sure how to fit them correctly in TOPAS as i dont know where to put the temperature information. Any kind of suggestion is really appriciated. -- thankyou, regards shishir
High temperature PXRD fitting in TOPAS
Hi, I have got high temperature Powder xrd data (from lab xray source) in the range of 30 ~1000 C . But i am not sure how to fit them correctly in TOPAS as i dont know where to put the temperature information. Any kind of suggestion is really appriciated. -- thankyou, regards shishir
Sources of standard reference materials
Hi All, Does anyone know an appropriate source of standard reference materials for a line profile standard, like NIST SRM 660a (LaB6) - other than NIST, as they are out of stock and ...is expected to become available by November 2009. Thanks, Ross
Re: High temperature PXRD fitting in TOPAS
Hi! I guess you have several diffractograms, don't you? you can work one by one your data, but first you must have data about the configuration of diffractometer or experimental data of an standard material like LaB6 and fit. after that you can replace the experimental data and fit. The temperature affects B ( thermal parameters), it is my suggestion, best ishes Miguel Hesiquio - Original Message - From: sisir ray To: rietveld_l@ill.fr Sent: Thursday, November 15, 2007 5:22 PM Subject: High temperature PXRD fitting in TOPAS Hi, I have got high temperature Powder xrd data (from lab xray source) in the range of 30 ~1000 C . But i am not sure how to fit them correctly in TOPAS as i dont know where to put the temperature information. Any kind of suggestion is really appriciated. -- thankyou, regards shishir
Fw: High temperature PXRD fitting in TOPAS
- Original Message - From: Miguel Hesiquio To: rietveld_l@ill.fr Sent: Thursday, November 15, 2007 5:44 PM Subject: Re: High temperature PXRD fitting in TOPAS Hi! I guess you have several diffractograms, don't you? you can work one by one your data, but first you must have data about the configuration of diffractometer or experimental data of an standard material like LaB6 and fit. after that you can replace the experimental data and fit. The temperature affects B ( thermal parameters), it is my suggestion, best ishes Miguel Hesiquio - Original Message - From: sisir ray To: rietveld_l@ill.fr Sent: Thursday, November 15, 2007 5:22 PM Subject: High temperature PXRD fitting in TOPAS Hi, I have got high temperature Powder xrd data (from lab xray source) in the range of 30 ~1000 C . But i am not sure how to fit them correctly in TOPAS as i dont know where to put the temperature information. Any kind of suggestion is really appriciated. -- thankyou, regards shishir
Amorphous content
Hi, I am trying to determine amorphous content using Rietveld refinement and internal standard. However resulting content of amorphous phase is really unrealistic. Moreover testing the method using standards with known amorphous content does not clarify the situation. For example ZnO (NIST, 95% crystallinity) used as standard to determine amorphous content in CeO2 (also NIST standard with 91% crystallinity) yield 25% of amorphous phase which is a little bit too much comparing with expected 9%. We tested several different standards, mixtures and preparations, different diffractometers and software without much luck... Seems like something simple is missing... Any clues? Many thanks, Peter Zavalij X-ray Crystallographic Laboratory Department of Chemistry Biochemistry 091 Chemistry Building University of Maryland College Park, MD 20742-4454 Phone: (301)405-1861 Fax: (301)314-9121 E-mail: [EMAIL PROTECTED] http://www.chem.umd.edu/facility/xray/
RE: Amorphous content
At first glance it looks like a classic microabsorption problem, but I don't have the linear absorption coefficients to hand. Using an internal standard with a too small absorption will tend to over-estimate the amorphous content. Ce versus Zn is a pretty big contrast for CuKa, even if the particle sizes are small enough. The whole point of that NIST series (674 I think) is that they were to be used as appropriate contrast matching standards for quant analysis, and were supposed to be quite different from each other. Changing the wavelength to reduce the contrast (e.g. Mo) may help for that particular mix but probably won't completely solve it. Pam From: Peter Y. Zavalij [mailto:[EMAIL PROTECTED] Sent: November 15, 2007 9:07 PM To: rietveld_l@ill.fr Subject: Amorphous content Hi, I am trying to determine amorphous content using Rietveld refinement and internal standard. However resulting content of amorphous phase is really unrealistic. Moreover testing the method using standards with known amorphous content does not clarify the situation. For example ZnO (NIST, 95% crystallinity) used as standard to determine amorphous content in CeO2 (also NIST standard with 91% crystallinity) yield 25% of amorphous phase which is a little bit too much comparing with expected 9%. We tested several different standards, mixtures and preparations, different diffractometers and software without much luck... Seems like something simple is missing... Any clues? Many thanks, Peter Zavalij X-ray Crystallographic Laboratory Department of Chemistry Biochemistry 091 Chemistry Building University of Maryland College Park, MD 20742-4454 Phone: (301)405-1861 Fax: (301)314-9121 E-mail: [EMAIL PROTECTED] http://www.chem.umd.edu/facility/xray/
Re: Sources of standard reference materials
Hello Ross For this purpose you can use annealed (1573K, 3h, in air) CeO2 (D. Balzar et al., J. Appl. Cryst. 37 (2004), 911-924), which is by far cheaper than the NIST standard, I suppose. Regards Franz -- GMX FreeMail: 1 GB Postfach, 5 E-Mail-Adressen, 10 Free SMS. Alle Infos und kostenlose Anmeldung: http://www.gmx.net/de/go/freemail
