Assaying, Microscopy, Mineralogy & XRF/XRD

Assaying, Microscopy, Mineralogy & XRF/XRD 2017-03-23T09:37:54+00:00
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XRF Data Interpretation and Understanding Results (3 replies)

David Kano
1 year ago
David Kano 1 year ago

I´m new in this interesting in Data Interpretation in qualitative analysis and hope you can help me with this:

I have a powder Ag sample (containing little quantity of Ag2O) and have performed a WDXRF qualitative analysis (Rhodium target) with the LiF220 analysing crystal. I can clearly identify the AgKalpha, AgKbeta (fisrt and second order), Rh Kalpha and RhKbeta peaks. My question is about the presence of two broad peaks around these º2theta positions: 30.56º and 34.76º. Might these be half order AgKalpha, Kbeta lines (forbidden reflections) due to inhomogeneities of the crystal? Is the first time I see them. 

Maya Rothman
1 year ago
Maya Rothman 1 year ago

That is possible. These two angles are the proper position of the 1.5 order of Ag KA and Ag KB on a LiF220. This is not due to inhomogeneity of the crystal but to the crystalline structure of the LiF220. With this type of crystal half-orders peaks can appear, especially with high concentration. This is only a diffraction effect caused by the crystal. The peaks should look wider than a 1st order peak.

Helena Russell
1 year ago
Helena Russell 1 year ago

Typically half orders (0.5th and 1.5th order) are a factor 100 weaker than the major lines. In some cases it may be that the 1.5 KA line is shifted e.g. -0.1 degrees wrt the theoretical angle where the 1.5 KB may be as much as 0.3 degrees off, where the whole orders are on their expected positions. You will find half orders especially on LiF220, they are much less common for other crystals. Half order K-lines will appear more clearly for high concentrations of heavy elements in light matrices.

David Kano
1 year ago
David Kano 1 year ago

Thank you all for these valuable contributions! In fact, I also analysed this sample with the LiF200 crystal and these peaks don´t appear.

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