July 2013


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"Andersen, Jens" <[log in to unmask]>
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JEOL-Focused Probe Users List <[log in to unmask]>
Mon, 29 Jul 2013 17:42:16 +0000
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Hi all.

I've been spending some time measuring indium (Lα)  in natural minerals, and (for those of you who tried this) you will be aware of the serious interference with Sn-Lη. There's no other significant x-ray line to use (apart from a minor Lβ4 line) So here comes the problem: when I measure stannite and cassiterite, the minimim "excess" indium concentration correlates very well with the Sn concentration and can be subtracted by a linear approximation. However, when measuring Sn metal, I get a significant additional surplus of indium that I can't explain. I'm pretty certain the the metal doesn't contain indium at the several hundreds of ppm level, as I've analysed several different standard reference materials from a variety of sources. All of the reference metals have this excess and are fairly constant with respect to this additional indium signal.

So what could cause this? I measure background positions on both sides of the peak, however I've been forced to put a background beyond the Sn-Lα peak. I checked for absorption edges, which are fine. I checked for minor metal substitution in cassiterite (notably Fe, Nb) which are not a problem. So what is it? Is the background shape particularly sensitive to the conductivity of the pure metal in contrast to the insulating cassiterite? Is the relative height of the Sn-Lη line influenced by the valency or bonding (metallic versus covalent)? 

I would be interested in any bright ideas to what could cause this.

Best regards, 


Jens Andersen
Camborne School of Mines
University of Exeter
Cornwall Campus
TR10 9EZ
01326 371 836