Re: XRF and XRD best practice...
The basic question how useful chemical analysis can be for quantitative phase analysis of rocks is simply the ratio between the number of phases and the number of main elements contained, i.e. the complexity of the system. If you have rocks containing a big number of minerals maybe having variable or unknown chemical formulae, and the number of unknowns is bigger than the number of main elements, than the linear equation system is under-determined and you can just calculate ranges of possible mineralogical compositions. But of course in fortunate, simple cases it is possible to calculate the mineralogical composition directly from the XRF analysis. In principle it is possible to add chemical constraints to a Rietveld refinement. However, in my experience the qualitative mineralogical analysis of rocks is a much bigger hurdle, and the typical uncertainties in qualitative mineralogical analysis and the uncertainties of average mineral formulae in complex rocks prohibit an effective use of this tool for QPA. Best regards Reinhard Am 14/02/2014 22:21, schrieb Łukasz Kruszewski: Hi. I think XRF can help only in case of simple samples or, e.g., to disclude some strange elements, by proving there's none of them in the particular sample. But when you have, lets say, a mixture containing a spinel and periclase (MgO), then you won't be able to confirm by XRF itself that all the Mg determined is cointained in periclase only, as spinels take Mg too. An EDS or WDS system would be better here, but of course it gives reasonable results for thin sections mostly. However, even tiny 3D chunks of a sample can be used to confirm the presence of the particular species you've included in the QPA refinement. Good luck! Luke Kruszewski Hello all, I use Rietveld primarily for quantitative phase analysis of rock samples. We collect XRF and XRD data on our samples. Is there a best practice for using these data together? Or a recognized method or procedure for evaluating the agreement between the two? Can the XRF be used to restrain the phase concentrations in a refinement? Thank you all for the years of advice I have gotten from this forum. All the best, Blaise -- TU Bergakademie Freiberg Dr. R. Kleeberg Mineralogisches Labor Brennhausgasse 14 D-09596 Freiberg Tel.++49 (0) 3731-39-3244 Fax. ++49 (0) 3731-39-3129 ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Re: XRF and XRD best practice...
There are many ways how elemental analysis (e.g. by XRF) can be used to guide the XRD phase quantification. This becomes especially relevant when using 2 in 1 equipment like Thermo ARL 9000 Workstation. The XRD-XRF combination is often used (by various ways) in cement industry - you may search for references from this field for a good start. The whole process becomes tricky when amorphous phase(s) is present as XRD obviously sees only crystalline part. Consequently, combining the two techniques, one can (often; by certain procedures) extract the amorphous phase content. _ Maxim V. Lobanov Department of Chemistry Moscow State University loba...@icr.chem.msu.ru Friday, February 14, 2014, 7:40:35 PM, you wrote: Hello all, I use Rietveld primarily for quantitative phase analysis of rock samples. We collect XRF and XRD data on our samples. Is there a best practice for using these data together? Or a recognized method or procedure for evaluating the agreement between the two? Can the XRF be used to restrain the phase concentrations in a refinement? Thank you all for the years of advice I have gotten from this forum. All the best, Blaise ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Re: XRF and XRD best practice...
Hi. I think XRF can help only in case of simple samples or, e.g., to disclude some strange elements, by proving there's none of them in the particular sample. But when you have, lets say, a mixture containing a spinel and periclase (MgO), then you won't be able to confirm by XRF itself that all the Mg determined is cointained in periclase only, as spinels take Mg too. An EDS or WDS system would be better here, but of course it gives reasonable results for thin sections mostly. However, even tiny 3D chunks of a sample can be used to confirm the presence of the particular species you've included in the QPA refinement. Good luck! Luke Kruszewski Hello all, I use Rietveld primarily for quantitative phase analysis of rock samples. We collect XRF and XRD data on our samples. Is there a best practice for using these data together? Or a recognized method or procedure for evaluating the agreement between the two? Can the XRF be used to restrain the phase concentrations in a refinement? Thank you all for the years of advice I have gotten from this forum. All the best, Blaise -- Łukasz Kruszewski, Ph.D., adjunct Polish Academy of Sciences Institute of Geological Sciences X-Ray Diffraction Laboratory (coordinator) Twarda 51/55 str. 00-818 Warsaw Poland ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
