General EPMA > EPMA Standard Materials
Standards Which Should Be Developed For EPMA Next
John Donovan:
By the way, I just had a nice chat with Julien Allaz, who as you may know is heading up the MAS FIGMAS effort (with Anette von der Handt and Owen Neill), to document our current standards and manage future efforts in developing new standards.
I just want to say for the record that I fully support their efforts and that our own efforts here to "jump the gun" and start thinking about new standards is just merely to "prime the pump" informally to get us all thinking and talking about opportunities for new, pure, robust and plentiful(!) standard materials for SEM and EPMA.
I would characterize the FIGMAS effort as the "formal" process, and our own small efforts a complementary "informal" process. My personal take is that although we absolutely need to document what we already have, before we can get really serious about new standards, we already know that there are specific elements in specific phases that we know we don't have any reasonable availability of. For example Rb and Cs primary standards. That is why I was so happy to obtain the RbTiOPO4 standard material that the Calchemist site is now offering at $100/gram.
http://www.calchemist.com/standards.htm
Cheap and significant quantities of pure standard materials is the goal!
I should also add that I personally have no interest in a Cs standard (though it is leading in our informal poll at the moment), but I do know that what's out there for Cs are only very small (flyspeck) quantities, of relatively poorly characterized natural materials. And since we already have a recipe for a Cs zirconyl phosphate phase, it might be one candidate new standard. Maybe.
Frankly I'd personally be more interested in a pure end member fayalite (Fe2SiO4) for testing matrix corrections, but I think it should be a community decision... depending on the difficulty of preparation of course, hence the poll here:
http://probesoftware.com/smf/index.php?topic=560.0
In any case, I would expect that if the MAS or FIGMAS group decides to perform a survey on what standard to develop next, it will be much more complete survey, with better statistics (one would hope anyway!). But this simple poll is just one small attempt to begin to "test the waters" as they say!
Julien said he is still working on the FIGMAS web site but will post something here as soon as he can. We of course are all very interested in what the future will bring...
crystalgrower:
Any combination of Cs and Zr and PO4 will give two phases: CsZr2(PO4)3 as already reported, and CsPO3. It is not a matter of heat or pressure, but cation radius.
Now there is a reliable published synthesis for Cs4Ba(PO3)6 which yes has a lot of EDS overlaps. Materials Research Bulletin vol 12 pages 13-16 in French. I would try Cs4Sr(PO3)6 using the same starting proportions and temperatures.
There are also reliable syntheses for Th(PO3)4 and U(PO3)4 Any takers?
FYI all the metaphosphates that I have suggested are totally insoluble. No colour centres when run on full scan XRF. They polish very well. They fit your cost profile. The people who have purchased rare earth ultraphosphates can vouch for longterm electron beam stability of similar compounds.
I know. They ain;t silicates.
Probeman:
--- Quote from: crystalgrower on January 26, 2018, 11:09:28 AM ---Any combination of Cs and Zr and PO4 will give two phases: CsZr2(PO4)3 as already reported, and CsPO3. It is not a matter of heat or pressure, but cation radius.
Now there is a reliable published synthesis for Cs4Ba(PO3)6 which yes has a lot of EDS overlaps. Materials Research Bulletin vol 12 pages 13-16 in French. I would try Cs4Sr(PO3)6 using the same starting proportions and temperatures.
There are also reliable syntheses for Th(PO3)4 and U(PO3)4 Any takers?
--- End quote ---
I'm interested in any high concentration Cs synthetic that is stoichiometric, non-water soluble and beam stable. The RbTiOPO4 is perfect is all these respects, but according to Marc Schrier there is no Cs analog of this Rb compound.
So if CsZr2(PO4)3 fits the bill with regards to stoichiometry, insolubility and beam stability, I would be very interested.
Or is there a Cs compound that is even higher Cs concentration? We were originally hoping for a CsZrOPO4 compound, but when Marc tried to synthesize it we got CsZr2(PO4)3 instead, so maybe that's the only choice in a Cs phosphate?
john
Probeman:
--- Quote from: Probeman on January 26, 2018, 11:20:25 AM ---So if CsZr2(PO4)3 fits the bill with regards to stoichiometry, insolubility and beam stability, I would be very interested.
--- End quote ---
I wonder if we could "crowd source" this project? What would you guess it would cost for you to make say 5 or 10 grams of this compound?
crystalgrower:
The Cs4Sr(PO3)6 calculates about 46% Cs.
It's straightforward to make in a Pt crucible. You need Cs2CO3 and SrO or SrCO3 and H3PO4 and a furnace that will hold at 400C. It takes a few hours to react the mixture on a hotplate to a stable liquid. Then you let it cook overnight at 400C.
Time depends on crucible size. Only caveat is that you must have pure Pt. The alloy used for XRF pellets will not survive for long with the P2O5 glass that is formed.
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