Probe Software Users Forum

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This is a popularity contest.  The most popular standard material will be developed next.

We're shooting for $100/gram for that are not water soluble and are beam stable. Please indicate your preference in the above poll.

Remember, our ability to develop this next standard depends on our "nest egg" funds from sales of the first "crowd sourced" RbTiOPO4 at $100/gram from The CalChemist site here:

http://smf.probesoftware.com/index.php?topic=301.msg2872#msg2872

Marc will need to purchase the starting raw materials from this "nest egg" for whatever standard is polled as next most desired.

Just out of curiosity, what's the interest in UO2?  Would another depleted oxide or phosphate work? -Marc

Please (if you haven't already), vote in the standards to be developed next poll here (you must be logged in to vote and/or see the poll results!):

http://smf.probesoftware.com/index.php?topic=560.0

to help us identify the next candidate material for standard development.  More materials could be considered but it's at least a start...

So far 13 people (out of ~300 members) have voted.  It would be nice to get a more comprehensive sampling!

Thank-you!

Bump.   ;D

Please vote in the standard material poll above if you haven't already.  Remember you have to be logged in to see the poll results or to vote.

http://smf.probesoftware.com/index.php?topic=560.0

john

It's a close race between the top three standard candidate materials:

http://smf.probesoftware.com/index.php?topic=560.0

Remember you have to be logged in to see the poll results or to vote!

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://smf.probesoftware.com/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...

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.

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?

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

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.   

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?

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. 

I'd definitely be willing to contribute to an effort to synthesize Cs4Sr(PO3)6, as I've been looking for a reliable Cs standard for a number of years.  I get 48.6 wt% Cs and 51.6 wt% Cs2O.

Quote from: crystalgrower on January 26, 2018, 05:01:36 PM
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.

I would contribute something as well for a Cs synthetic if you think Cs4Sr(PO3)6 would be stoichiometric.  Do you know if it is stable under the beam and non water-soluble?

Right now I will say this

1. The Cs4Sr(PO3)6 is stoichiometric and not water soluble. Other oligophosphates I made are beam stable single crystals.

2.  Those of you who bought REEP5O14 standards between September 2009 and December 2011 were buying my work.  Of course the products only bore the company name. 

3. I have sufficient feedback here to try a batch when the weather improves in March or April (garage operation). Batch size would be 5 grams or so.

4. I'm in Toronto so I will contact Brian Joy off line to discuss assistance.  I have the raw materials. 

Thorium: The Taylor collection had large quantities (~300 grams) of ThO2 that had been cut into 2mm cubes.  These appear to all have ended up in the subset purchased by Astimex.  The material has been used longterm for probe, it is sintered from grains and takes a good polish.  The 2mm x 2mm face shows as about 8 grains after polishing. 

Maybe somebody can invite them to see if they want to sell groups of 5 cubes for a special price?  5 cubes would be close to a gram.   The advantage is that synthesis of any other phase would require very costly waste disposal. 

And how do people feel about simple compounds?  Oxides vs fluorides vs sulfies vs silicates?

Here's a variation on a crazy idea from Donovan...

As we know, trace element accuracy is possible in EPMA but there are a number of artifacts that can make such analyses problematic. Depending on the specific matrix involved there may be issues with off-peak background positions, on-peak interferences, sample (and detector) absorption edges and beam sample sensitivity to name just a few.

Therefore many of us are seeking secondary standards for checking our trace element accuracy in EPMA.  The problem of course is that getting homogeneous (and accurate) trace element standards is difficult.  For both natural and synthetic materials we have problems with inclusions or contamination and heterogeneity. Then there are the issues with knowing what the trace element level actually is.  Is it 110 PPM or is it 115 or 105 PPM?  Who knows?  Every technique has its systematic errors.  This is discussed in some length in this topic here:

http://smf.probesoftware.com/index.php?topic=928.0

But there are two values that we can know with very high accuracy, First we can know something is 100% with extremely high accuracy.  For example, if our Si or SiO2 EPMA standard has been analyzed for possible contaminants and all are less than a few PPM, then we can be pretty confident that our Si is 99.99% Si or our SiO2 is 99.99% SiO2 (or however many 9s we checked for).

Likewise, we can also know that something is *zero* with extremely high levels of accuracy.  In fact in these cases we can have trace element accuracy *equal* to our measurement precision level, by simply using a matrix matched pure synthetic blank standard.

For example, if we use highly sensitive techniques such as ICP-MS on a pure synthetic standard material, and we know that our possible contaminants (that is, trace elements of interest) are well below the detection limit of the microprobe (let's say 1 PPM), then by measuring a pure synthetic standard which is similar to our matrix and carefully analyzed so we know the traces are below EPMA sensitivity, we can now check the accuracy of our EPMA trace element measurement by simply seeing if we can measure zero. If we do not obtain a zero measurement, then something is wrong, perhaps the background is curved (it always is!). Or there's a spectral interference, etc., etc.  This of course is where the blank correction in PFE can be applied to correct our unknowns.

For very simple unknowns such as measuring traces in say quartz, we are already fine, because there are many highly pure SiO2 materials available at low cost.  But that is not the case for other materials of interest.

Let's take a simple case of measuring traces in say olivine.  We'd like to have matrix similar to our unknown. But growing a homogeneous olivine of intermediate composition is difficult. There's always some zoning in an MgFeSiO4 composition, but wait! We don't care what the major element composition is, we only care about the trace elements in some olivine composition.  That is we really only care that the trace elements Mn, Ni, Cr, Al, Ca, etc. are below the detection limit for EPMA.  That way we can check our trace element accuracy in a matrix matched standard because we know regardless of the actual Fe-Mg ratio, we should obtain zero +/- the measurement precision.

In fact, we would actually *want* our olivine trace element standard to have a range of composition!  Why? Because then we can find an appropriate Mg rich or Fe rich (matrix matched) area of our synthetic olivine to test our zero measurement accuracy!

Now let's take a nasty case of trace U and Pb in monazite. Traditionally we would try and obtain a perfect homogeneous synthetic monazite that is accurately doped with the trace elements of interest.  But that is extremely difficult to synthesize.  It is usually highly zoned in major element composition (and trace elements) and therefore it can not really be considered a standard.

But, as long as the trace elements in question (say U and Pb), are *not* present at EPMA detection limits- it does not matter!  Again, by having a highly zoned synthetic monazite that we know is free from U and Pb, we have the perfect standard to check our trace element accuracy and we can probably find an intermediate composition of Ce, Nd, Gd, Sm, Th, etc. phosphate, that is a close matrix match to our actual unknown and we have high accuracy for zero concentrations of U and Pb.

We can continue the same line of thinking to traces in alloys, traces in sulfides, etc.  Again: the actual composition doesn't have to be an exact match (or even known accurately for that matter). What really matters is that the trace elements of interest are below EPMA detection limits in a similar matrix.

So what I think we really need are highly purified starting materials, and then synthesize some olivines, monazite, etc. for use as secondary trace element standards, to test our trace accuracy determinations in a close matrix match material.

As has been said before:  "if you can't measure something, try measuring nothing, because if you can't measure nothing, you can't measure anything".  And I would take it one step further: " for best accuracy, try measuring nothing, in a matrix matched pure synthetic material".

Hey I told you it was crazy!   :)     What do you think?

I agree completely.

In addition, please note that XRF-WDS is a fast and sensitive tool for the trace impurities in both starting materials and final crystals.  Loose grains give a very reliable result if they are anywhere near heat stable. If you are lucky then the peak and bgd settings are close to those used for EPMA.  I think that unless you are using LA, then ICP-MS is good for some starting materials but by no means all products. 

I have been working on monazite synthesis on and off.  Have some good starting materials and a process to recrystallize into mm size crystals.  Process will restart in the fall after I finish moving.

Right now a wishlist for monazite would be helpful.  Th-free?  High-Th (12%) ?  Mid-Th (8%)? Low-Th(4%)?  La-Ce-Nd synthetic  mix to correct assays of other trace REE?

And oh yes single element RPO4 for La-Gd would also be part of the project.  Free of any flux traces, of course.

Yes, this is a very interesting approach John.  The zero test tells you a lot, and, as you suggest, the analysis of inhomogeneous materials can be quite useful indeed, and matrix matching is a critical part of this.  Of course, synthetic monazite would be useful as suggested by crystalgrower, maybe even as a primary standard if it could be synthesized homogeneously.  Any such reference material for blank testing, however, would need a range of Th concentrations, and a few wt.% Y, and at least a typical La, Ce, Nd concentration.  The range of Th in natural monazite can be very large (less than 1 wt.% to almost 20 wt.% but is most typically in the 1-8 wt.% range.  The measurements of Pb and U are complicated by interferences by Th and Y mostly, and in the case of UMb, by the Th M4 and M5 absorption edges.  When Philippe Goncalves synthesized some monazite here years ago, he could get the REE phosphates, and a mixed LREE phosphate, but adding Th became interesting as the products were very heterogeneous.  But this is still useful as you suggest!

Quote from: Mike Jercinovic on July 30, 2018, 01:33:23 PM
Yes, this is a very interesting approach John.  The zero test tells you a lot, and, as you suggest, the analysis of inhomogeneous materials can be quite useful indeed, and matrix matching is a critical part of this.  Of course, synthetic monazite would be useful as suggested by crystalgrower, maybe even as a primary standard if it could be synthesized homogeneously.  Any such reference material for blank testing, however, would need a range of Th concentrations, and a few wt.% Y, and at least a typical La, Ce, Nd concentration.  The range of Th in natural monazite can be very large (less than 1 wt.% to almost 20 wt.% but is most typically in the 1-8 wt.% range.  The measurements of Pb and U are complicated by interferences by Th and Y mostly, and in the case of UMb, by the Th M4 and M5 absorption edges.  When Philippe Goncalves synthesized some monazite here years ago, he could get the REE phosphates, and a mixed LREE phosphate, but adding Th became interesting as the products were very heterogeneous.  But this is still useful as you suggest!

Cool.

So crystalgrower should look at synthesizing something along the lines of the chemical ranges you suggest, but she should just be sure to obtain U and Pb free starting materials.

Of course the final products can be checked for U and Pb to be below EPMA sensitivities using mass spec techniques in any case.

Yes, U and Pb free would be great.  But after that, some U bearing, with and without Th, would be awesome as these actinides are so intertwined.  Now and then, we see a monazite with more U than Th in nature, but this is important just to sort out actinides at high spatial resolution in general - that is, lower kV so not using the U L line.  We want everything of course, whether is it reasonable or not!  hashtag delusional...

Quote from: Mike Jercinovic on July 30, 2018, 06:55:45 PM
Yes, U and Pb free would be great.  But after that, some U bearing, with and without Th, would be awesome as these actinides are so intertwined.  Now and then, we see a monazite with more U than Th in nature, but this is important just to sort out actinides at high spatial resolution in general - that is, lower kV so not using the U L line.  We want everything of course, whether is it reasonable or not!  hashtag delusional...

Yes, but since it's difficult to produce non-zero values (and maybe even impossible to dope trace levels homogeneously in some materials), but easy to produce (homogeneous) zero values. Let's start with easy!    :)

Sometime in the next few weeks I will post a table of ideas.

I made one big mistake last time I made mixed cation phosphates--I did not ask enough people for ideal compositions of mixes.  At that time I had a set of single element EDS spectra to test overlaps by plotting, but no WDS.  Got those right after I finished a 2010 AGU poster...

I found a way to separate black crystals  (I suspect UO2) from natural monazite.  That means the U can be crystallized into something like Ca(Bi,U)(PO4)2.  The Pb would be the natural "old" mineral amount--please advise if that is acceptable.

The "natural" monazite is a lower priority--I was thinking of recvrystallizing it with added Ca to improve homogeneity without losing too much of the Th.  Only the natural accumulated Pb would be present.  It would be Si-free.

Synthetics are in my world made from "clean" materials.  That means using at least 99.99% Nd and Pr.  NO Pb in any reagent, and NO U in the Th. 

There is one exception--any Th would have some Ra present since it ingrows quickly to equilibrium.  I could remove natural decay product Ra and Pb if that is considered part of the Pb-free requirement.  But the final material would have Ra present.

Hi CG,
That sounds great if you can produce synthetic monazite with no Pb or U.

Again, for the purposes of testing our zero measurements in monazite, we would like highly zoned crystals that include the elements that Mike mentioned above, and also that cover the compositional ranges he discussed. Do you think this is possible?  Or would it require more than one synthesis?

I'll bet you never thought you'd be asked to grow *zoned* crystals!  But as long as they are U and Pb free, they would be perfect for testing our backgrounds and interference corrections. This material could add a whole new level of accuracy to our trace monazite measurements.
john

Welll...if you insist...

I actually grew a layer of pure CePO4 on top of a natural monazite recently.  Which probe experts want to play with this?  I don't know what the gradient looks like. I have never been allowed to use the local EPMA or SEM. 

Quote from: crystalgrower on August 01, 2018, 01:04:34 PM
Welll...if you insist...

It would be totally awesome if you could develop such a material.  So can that range of monazite compositions, that Mike described above, be created in a single synthesis?  This might even be worth a short paper if you are interested.

Quote from: crystalgrower on August 01, 2018, 01:04:34 PM
I actually grew a layer of pure CePO4 on top of a natural monazite recently.  Which probe experts want to play with this?  I don't know what the gradient looks like. I have never been allowed to use the local EPMA or SEM.

I defer to Mike Jercinovic on this question, but I suspect that anything involving natural compositions won't be all that useful, as we need to really need to know "a priori" that there is zero U and Pb in the blank material for testing zero measurement accuracy.

But maybe this type of material would be interesting for a different experimental measurement?  Not being a geologist I can't really say, but I will give it some thought.
john

I suggested a material which is already made to see if any improvements are needed.  I understand that it is not ideal.  But it will make a useful first trial.  I just cannot assess it myself. One of the two layers is certainly free of Pb and U. The other is from Petaca  NM which has been dated and assayed before.  There is also some of the "clean" CePO4 to test separately for absence of U and Pb.

Quote from: crystalgrower on August 02, 2018, 01:10:33 PM
I suggested a material which is already made to see if any improvements are needed.  I understand that it is not ideal.  But it will make a useful first trial.  I just cannot assess it myself. One of the two layers is certainly free of Pb and U. The other is from Petaca  NM which has been dated and assayed before.  There is also some f the "clean" CePO4 to test separately for absence of U and Pb.

Hi CG,
I appreciate that.  Thanks.

The thing is, in order to test our zero measurements we need a synthetic monazite that has the all the elements that Mike mentioned and in the ranges that he mentioned.  Basically a zoned synthetic monazite that we *know* does not contain *any* Pb or U. 

This will allow us to test the absolute accuracy of the background positions for off-peak interferences and also test the absolute accuracy of the interference corrections for on-peak interferences.   Unfortunately a pure CePO4 doesn't really test either of those issues. And in the case of the natural composition seed crystal, knowing that the natural monazite core been analyzed previously doesn't help us either, because we can only truly trust a value of "absolute" zero (or at least a value less than the best possible EPMA sensitivity). 

As Mike said when I discussed this with him a few days ago, this sort of accuracy test is a very different way of approaching trace element standards and therefore requires a very different type of standard material than we traditionally utilize for EPMA trace element measurements.

If you want to call me some time please feel free and I can probably explain it better by skype or phone.

Right, the CePO4 is certainly not that good a material for the blank test, but is, of course excellent as a primary standard (same with all the REE phosphates).  We also have a piece of the Petaca NM monazite, which is both heterogeneous compositionally as well as having lots of inclusions...  looks a lot like some of the other large pegmatite monazites from northern NM (like the Wards, Elk Mt. monazite).  Not a super useful one for us compared to some of the cleaner ones from Brazil (Minas Gerais).  Natural monazite is very useful as a secondary reference material.  For the blank testing, a synthetic monazite with at least LREEs, Th, and Y is certainly most useful.  As John says, heterogeneity is fine (even preferable), or at least of range of Th/LREE.

This is exactly the kind of detailed info that I need.  I need to use the pure CePO4 as seeds.  You can ignore its presence. 

So to confirm:  I should start with a layer of pure La-Ce-Nd-Y mix (free of U and Pb) and then add Th+Ca.  Do you care if the Ce+3 goes to Ce+4 in that Th layer? (means slightly higher Ca). 

Extra base mix can be run by XRF to show traces present. 

Yes, awesome.  The Ce+3 to Ce+4 should not matter.  Only a few wt.% Y at most.  I don't think the structure will accommodate a much larger amount anyway and still stay monoclinic.