Probe Software Users Forum

Quote"Houston, we have a problem" – Jack Swigert, Apollo 13

We also have a problem, though hopefully not one of life or death. However, it is a serious problem and one that requires our collective attention. It is a question of accuracy in the field of microanalysis.

Let's start by asking what might be the largest source of inaccuracy today in microanalysis.

Some of us would say: by *not* using standards. That is, standardless EDS analysis. Unfortunately we seem to have reached an impasse on what can be done about this situation (aside from getting EDS vendors to remove the "Quant" button and getting every SEM lab to obtain proper standards!), so let's put this aside for now, more on this later.

Then what might be the second largest source of inaccuracy in microanalysis today? We would suggest: by using standards!  Now what could we possibly mean by this statement?

Well, 40 years ago there was another problem in microanalysis. Namely that the analytical physical models for matrix corrections at that time were simply not very good. To address this issue, various empirical and semi-empirical methods were developed and tried (e.g., alpha factors, calibration curves, ZAF, etc.). But most of the time, for high accuracy work in these early days, it was usually necessary to utilize "matrix matched" standards. That is, find some "known" material that was similar to our unknowns, in order to minimize the matrix correction extrapolations from the standard to the unknown.  As we all know, if the unknown is the same composition as the standard, the matrix correction is exactly 1.000.

So what did people do? Well, heroes such as Gene Jarosewich and others went into their mineral collections and picked out some large, well crystallized natural specimens and diligently performed wet chemistry and other characterization on the pulverized material. Many of us have made similar efforts in our own laboratories to find such "matrix matched" standards.

Unfortunately these natural materials often had trace and minor element impurities, were inhomogeneous and zoned, containing various inclusions of different minerals and like the restaurant review we've all heard about: the food was terrible, and the portions small. That is, when a request for standard material was made, we would often only receive tiny flyspecks.

Since that time we have been the beneficiaries of many advances in the physical models for matrix corrections (e.g., phi-rho-z models such as PAP, XPP, Brown, Armstrong, improved mass absorption coefficients, improved fluorescence corrections, etc.), so that today we can often obtain accuracy better than 2% relative in most matrices. Sometimes, especially for minor and trace elements, our accuracy is only limited by our measurement precision!  So such "matrix matched" standards are often no longer necessary in many cases. But what is necessary are large quantities of high purity, high accuracy standards!

But here we are today still relying on these sometimes poorly characterized, natural, impure, heterogeneous, inclusion ridden standard materials (and such small portions!), which are now arguably a major source of inaccuracy in our field. See Fournelle, J., & Scott, J. (2017).

Note: due to differences in chemical bonding and coordination, there  can be subtle peak shift and shape effects, and therefore we  may still be required to utilize oxide and silicate standards for analyzing oxide and silicate materials, and sulfide and sulfosalt standards for analyzing sulfide and sulfosalt materials, etc. We can probably live with that!

For possible evidence of these issues see Gale et al., (2013) "The mean composition of ocean ridge basalts" and also Yang et al. (1996) "Experiments and models of anhydrous, basaltic olivine-plagioclase-augite saturated melts from 0.001 to 10 kbar" where they state: "An interlaboratory comparison has been made (Reynolds 1995) including MIT, the Smithsonian Institution in Washington, Lamont Doherty and University of Hawaii. It is the practice in our laboratory to correct microprobe data obtained elsewhere to an MIT reference before making thermobarometric or modeling analyses (see Table 1). Although Grove et al. (1992) neglected to discuss this issue, the Smithsonian data discussed in that paper was corrected before plotting and estimation of crystallization pressure. Failure to do so can result in significant errors, and is most commonly evident as a discrepancy in the pressures estimated from the different equations". Also please see figure 1 below from Penny Wieser for a graphical representation of these various interlaboratory biases.

So what can be done about this situation? Well, notable efforts have been made at NIST to synthesize mineral glass standards, e.g., K-411, K-412 and more recently at the USGS basaltic glasses BCR-2G, BHVO-2G and BIR-1G and these glasses be very useful standards if produced in sufficient (kilogram) quantities so that every microanalysis lab on the planet can obtain them. Compositional characterization of such glasses is however quite non-trivial, but can be done with enough effort. If only such glasses were available in kilogram quantities and freely available. Indeed if they are available in such large quantities, they should be part of every standard collection, but apparently they are not. So what might we do?

We propose that a modest to moderate investment by our international microanalysis community can provide high purity, high accuracy standards for current and future generations of microanalysts.

We propose by utilizing high purity synthetic single crystal materials produced in kilogram quantities every microanalytical laboratory in the world could have access to the same standards. Such end-member single crystals of high purity can be, unlike glass standards which require further compositional characterization, already known in composition!

Note: some questions have been raised as to the degree of, or closeness to, stoichiometry of industrially-produced synthetic materials. Specifically, to what accuracy can the chemical stoichiometry of such single crystals be determined? For example, if a high purity single crystal is homogeneous on the micro-scale, is it also likely to be chemically stoichiometric? This will require further investigation.

E.g., high purity, single crystal Mg2SiO4 should be exactly Mg: 34.550 Si: 19.962 O:  57.143 weight percent (assuming accepted terrestrial isotopic distributions!). And it is grown industrially today as a laser material.

We propose to invest in high purity, stoichiometric (thermodynamically constrained end-member), synthetic standard materials produced in kilogram quantities. Specifically, pure enough single crystals so that homogeneity is not in question (though both purity and homogeneity can be checked), and enough quantity so that *every* microanalytical laboratory in the world has access to the *same* primary standards. In other words, the global standardization of microanalysis, much as was done hundreds of years ago for the metric system, when there were no global standards for commercial or scientific weights and measures. Call it the metrification of microanalysis standards if you will.

We do not propose that these materials be produced in academic/government laboratories; most do not appear set up for kilogram production quantities. However we would very much depend on the expertise of those individuals among our colleagues who are experienced in the growth of such materials to advise us as to what synthetic minerals may be commercially possible. 

Instead, we propose that there are sufficient industrial/commercial resources capable of producing semi-conductor and optical/electronic materials, so that we could contract out the production of such high purity single crystal boules for these standard materials. What standards should we invest in producing?  That is a good question. We think this is for us as a community to decide. Some polling on this question should be organized.

We might guess that the average cost of the synthesis per kilogram of such high purity synthetic standard materials might average around $10K each (pers. comm., Marc Schrier, Calchemist).  Some materials are already available (e.g., SiO2, MgO, Al2O3, MgAl2O4, Mg2SiO4, YAG, YIG, Fe2O3, TiO2, SrTiO3, RbTiOPO4, KTiPO4, MnO, Fe3O4, NiO, ZnO, LaAlO3, MnPSe3, LiTaO3, etc.) and will be a fraction of this cost and can be bought "off the shelf".

Other synthetic minerals may require further research and development, e.g., ZrSiO4 (zircon), ZrO2 (zirconia), HfSiO4 (hafnon), HfO2 (hafnia), ThSiO4 (tetragonal thorite), ThSiO4 (monoclinic huttonite), Fe2SiO4 (fayalite), Mn2SiO4 (tephroite), CaMgSi2O6 (diopside), Al2SiO5 (sillimanite), NaAlSiO4 (nepheline), KAlSi3O8 (sanidine), KAlSi2O6 (leucite), KAlSi3O8 (orthoclase), NaAlSi3O8 (albite), CaAl2Si2O8 (anorthite), Fe3Al2Si3O12 (almandine), PbSiO3 (alamosite), CaAl2O4 (krotite), CaAl4O7 (grossite), CaAl12O19 (hibonite), CaSiO3 (wollastonite), MgSiO3 (enstatite), FeSiO3 (ferrosilite), sulphides (which are seriously lacking since the pioneering days at the USGS-Reston in the 1970s by researchers including Barton, Skinner, Czamanske, Bethke, Toulmin, among others), tellurates, arsenides, niobates, tantalates, etc., may cost 2 or 4 or 10 times this. Let's do more research on what might be possible at a reasonable cost.

The point being that with further research we believe that other high purity single crystal materials can be identified, developed, characterized and included as useful microanalysis standards in large quantities for use worldwide.

As former directors and presidents of several microanalysis societies, we know the money is available. For example we believe that the Microbeam Analysis Society has accumulated an order of magnitude more money in their funds than would be necessary to fund such a project. By spending around 10 to 30% of just the MAS funds we could secure the global future of high accuracy microanalysis for generations.  If several other national microanalysis societies join this effort, the cost to each society will be an even smaller percentage, and all will benefit.

It should also be noted that such high purity materials could also serve additional purposes such as:

1.   Primary standards to check the compositions of the current standards in every microanalytical lab. If we all are not utilizing the *same* primary standards, what is the point of comparing them?

2.   Primary and secondary standards as a test bed for the community consensus k-ratio database as proposed by Nicholas Ritchie. This means we should strive for at least two standards per element in this effort!

3.   "Blank" materials for trace element analysis and also for mean atomic number (MAN) background standard materials. Six or more "nines" purity is required for use as a trace element blank.

4.   Having these end member high purity synthetics (and maybe some glasses) will really stress our EPMA matrix corrections, dead time calibrations, beam current (Faraday Cup) linearity, not to mention effective takeoff angles and stage tilt on SEM instruments. Such failure mode analysis is essential if we are to make progress in improving these areas of instrumental calibration.

5.   It should also be noted that unlike the "historical accidents" of many of our current standards available today (which are very unlikely to ever be re-created with the same exact compositions), the future production of high purity, single crystal, and thermodynamically constrained standard compositions can always be repeated in the future if necessary. E.g., high purity MgAl2O4 will always be high purity MgAl2O4.

Some possible other items to consider:

6.   The MASFIG committee should establish the minimum qualifications for a candidate standard material to be included in the archive: e.g., characterization by XRD for a crystalline material; independent elemental analysis for a glass; trace measurements by WDS/ICP-MS to establish minimum detectable limit for a specified suite of elements.

7.   It should be noted that in the area of synthetic minerals there are basically two types of candidates: (a) materials already produced at an industrial scale and readily available in kilogram quantities at a fairly reasonable prices (e.g., MgO, Al2O3, MgAl2O4, TiO2, SrTiO3, etc.), and (b) those that are only produced in experimental laboratories in limited (e.g, grams to tens of gram) amounts (e.g., Mg2SiO4, Fe2SiO4, ZrSiO4, Al2SiO5, CaMgSi2O6, etc.).

It must be said that we should probably first concentrate on those materials that are already available in sufficient quantities with reasonable prices to begin with, and then follow up with consultation and investigation of other possible synthetic minerals based on their feasibility of being produced in sufficient quality and quantities.

8.   Establish an on-line database for the information on each standard material, perhaps supported by a non-fungible digital token (NFT) that documents the composition and any other issues, e.g., dose sensitivity, surface layers, etc. This database could include approved additions of information to the analytical record for each material supplied by users. FIGMAS already has a framework for this process.

9.   Establish a site for the repository of the materials, located at a university, museum or national laboratory. 

10.   Establish a strong mechanism for making these standard materials available to customers worldwide, e.g., create working relationships with the vendors who currently provide prepared microanalysis standards. A participating vendor would be given a quantity of the standard material that could be included in that vendor's prepared microanalysis standards for distribution. A portion of the material supplied to the vendor should also be available for interested customers to purchase (at a nominal cost to cover the vendor's expenses) individual rough pieces suitable for mounting and polishing by the customer.

11.   These materials may also be useful for other methods of characterization, i.e., Raman spectroscopy, Infrared specular reflectance spectroscopy, Infrared ATR spectroscopy (as powdered material), etc.

Regardless, this is a global analytical issue affecting the microanalysis community. Every microanalysis lab should be able to reference the same primary standard materials if we are to attempt to properly compare our data and results.  If such standard materials are readily available in kilogram quantities, then not only every EPMA lab, but every SEM lab should be able to utilize the same reference materials. Now that would be something worth having for a truly global science of microanalysis.

We are currently in the gathering ideas phase. This effort is clearly one that will foster lots of interest from our community and beyond (as we should hope, with a project such of large scope as this). Please post your comments and ideas to this topic and let's begin the discussion on how to finally move forward on this critical aspect of our field.
This is an investment not only for ourselves, but for the future of our science, so please join us in these efforts and change the world for future generations (of analysts) to come. They will thank us!

Signed,

Marisa Acosta, University of Lausanne
Dave Adams, Auckland University
Julien Allaz, ETH Zurich
Renat Almeev, Hannover of University
Paul Asimov, California Institute of Technology
Aaron Bell, University of Colorado
Joseph Boro, University of Hawaii
Scott Boroughs, Washington State University
Emma Bullock, Carnegie Institution of Science
Paul Carpenter, Washington University
Henrietta Cathey, Queensland University of Technology
Dave Crabtree, Ontario Geological Survey
Joel Desormeau, University of Nevada, Reno
John Donovan, University of Oregon
Mike Dungan, University of Oregon
Paul Edwards, Strathclyde University
Jon Fellowes, University of Manchester
John Fournelle, University of Wisconsin
Zack Gainsforth, University of California at Berkeley
Raynald Gauvin, McGill University
Karsten Goemann, University of Tasmania
Stacia Gordon, University of Nevada, Reno
Dick Grant, Sandia National Laboratory
Juliane Gross, Rutgers University
Jakub Haifler, Masaryk University
John Hanchar, Memorial University of Newfoundland
Jason Herrin, Nanyang Technological University
Heidi Hoefer, Frankfurt University
Julia Hammer, University of Hawaii
Eric Hellebrand, University of Utrecht
Dominik Hezel, University of Frankfurt
Raymond Jeanloz, University of California, Berkeley
Mike Jercinovic, University of Massachusetts
Brian Joy, Queen's University
Stuart Kearns, University of Bristol
Adam Kent, Oregon State University
Michael Lance, Oak Ridge Laboratory
Donovan Leonard, Oak Ridge National Laboratory
Yanan Liu, University of Toronto
Xavier Llovet, University of Barcelona
Andrew Locock, University of Alberta
Heather Lowers, United States Geological Survey
Chi Ma, California Institute of Technology
Danny MacDonald, Dalhousie University
Ryan McAleer, USGS, Reston
Mike Matthews, Atomic Weapons Establishment
Francis McCubbin, NASA, Johnson Space Center
Andrew Mott, Texas A&M
Aurelien Moy, University of Wisconsin
Timothy Murphy, Macquarie University
Will Nachlas, University of Wisconsin
Owen Neill, University of Michigan
Angus Netting, University of Adelaide
Dale Newbury, National Institute of Standards and Technology
Phil Orlandini, University of Texas, Austin
Changkun Park, Korea Polar Research Institute
Anne Peslier, NASA, Johnson Space Center
Glenn Poirier, University of Ottawa
Xiaofei Pu, Idaho National Laboratory
Ron Rasch, University of Queensland
Minghua Ren, University of Nevada, Las Vegas
Paul Renne, Berkeley Geochronology Center
Nicholas Ritchie, National Institute of Standards and Technology
Malcolm Roberts, University of Western Australia
George Rossman, California Institute of Technology
Dawn Ruth, USGS Menlo
Gareth Seward, University of California, Santa Barbara
Lang Shi, McGill University
Tom Sisson, USGS Menlo
Giovanni Sosa-Ceballos, , National Autonomous University of Mexico
John Spratt, London Museum of Natural History
Frank Tepley, Oregon State University
Edward Vicenzi, Smithsonian Institution
Anette von der Handt, University of Minnesota
Benjamin Wade, University of Adelaide
Richard Walshaw, University of Leeds
Penny Wieser, Oregon State University
Axel Wittmann, Arizona State University
Karen Wright, Idaho National Laboratory
Panseok Yang, University of Manitoba
Shui-Yuan Yang, China University of Geosciences
Marty Yates, University of Maine
Keewook Yi, Korea Basic Science Institute
Ying Yu, University of Queensland
Zhou Zhang, Zhejiang University
Ryan Ziegler, NASA, Johnson Space Center

(https://smf.probesoftware.com/gallery/395_18_11_21_11_28_07.png)

Fig 1 - Assessing the effect of interlaboratory biases on Cpx-only and Cpx-Liq thermobarometery using the average reported Cpx and Liq composition from the experiments of Krawcyznski et al. (2012) analyzed on the MIT microprobe.

(a-b) Interlaboratory correction factors for glass from Gale et al., (2013) relative to the Lamont microprobe (plotting at 1, 1).

(c-d) Calculated Cpx-only and Cpx-Liq pressures and temperatures for the average reported composition from Experiment 41c-106, corrected as if these materials were measured in the different laboratories shown in a-b. We assume the Cpx and Glass offsets between different laboratories are identical, as to our knowledge no Cpx round robin has ever taken place.

(e-f) as for c-d, using experiment 41c-108b.

Calculating pressures can vary by ~4 kbar and 50 K just depending on which microprobe analyses were performed on. These systematic offsets between laboratories likely increase the amount of noise in experimental datasets compiled from different laboratories when calibrating different thermobarometric expressions. Similar systematic offsets in pressure and tempreature space can be expected for different groups measuring Cpx and Glass compositions in natural samples to calculate pressures and temperatures. 

For example, for a given natural Cpx composition,  the MIT microprobe might yield ~12.5 kbar, while the Lamont microprobe would yield ~10 kbar (c). These potential offsets largely cannot be corrected retrospectively, as there is insufficient data on the magnitude of offsets between different EPMA laboratories for different geological materials.

See attached pdf (please login to see attachments).

Comments and suggestions for moving forward with this global project are welcome.

Our next efforts will be focused on obtaining some modest amounts (a few grams each?) of 7 or 8 commercially available high purity synthetic materials for mounting to begin their initial characterization.

If anyone can locate or obtain a few grams of these (or other) readily available high purity synthetic materials, please comment below. The idea being a limited set of initial test materials that could be utilized to produce several k-ratio measurements on TAP, PET and LiF Bragg crystals by FIGMAS or other MAS/EMAS/AMAS/JSM/KSEM, etc., members. Also enough extra material to also perform ICP/MS to check for trace elements, XRD for crystallinity, etc...

MgO, Al2O3, MgAl2O4, SiO2, TiO2, SrTiO3, Fe2O3, Fe3O4, YIG, YAG, etc.

Will Nachlas will be coordinating this effort. Please contact Will directly and/or send candidate materials to:

Will Nachlas
Weeks Hall for Geological Sciences
1215 West Dayton St
Madison WI 53706

Will Nachlas <nachlas@wisc.edu>

Thanks for organizing this John.  It is an important endeavor that will ground the technique for decades to come.

hi John

I'm broadly sympathetic but I have a few comments.  Firstly, there is a need for microanalytical standards particularly in the LA_ICPMs world and particularly for metals and sulphides. Unfortunately, and for obvious reasons, these are never homogeneous at the scales required - some elements are better than others (like Cu in sulphides) but others are a perennial problem and thats not an easy one to fix.

Secondly, I'm not sure the inclusion of lab comparisons for the CPX barometry is actually that helpful to the cause. You could also include redox sensors in this, but the problems are more protracted as a critic/reviewer may want to look at the accuracy of the experimental data and point an initial finger there, rather than, say,  just the lack of standards.For instance, what is the true error on Pressure and temperature in the experiments how much does grain size in the natural samples/volatile content/prep play a role etc etc.  In reality a single reference secondary standard would provide intra-lab/run consistency and it doesn't really have to be that 'good'. Many groups already offer their published materials as 'standards', such as Mossbauered synthetic spinels or oxygen bearing sulphides.  Yes, they may not always be that great, but they do provide a common reference point and their availability is often key to publication.

finally - why crystals?  why not glasses?  why the extra effort to synthesise a  crystal that will often require a flux? and why the amount?  is there really a need for kg's of sample which will inherently present more issues of homogeneity when a few grams will keep us happy?  they are, after all, micro analytical standards. ;)

Hi Jon,
We appreciate any and all comments. I will try to answer them as best I can, though perhaps I should start by pointing out that participation in this global standards project is completely voluntary.  You can of course continue to utilize your existing standards!   :)

Quote from: jon_wade on November 19, 2021, 02:26:41 PM
I'm broadly sympathetic but I have a few comments.  Firstly, there is a need for microanalytical standards particularly in the LA_ICPMs world and particularly for metals and sulphides. Unfortunately, and for obvious reasons, these are never homogeneous at the scales required - some elements are better than others (like Cu in sulphides) but others are a perennial problem and thats not an easy one to fix.

I don't see why you would say that metals and sulfides are obviously never homogeneous. Pure metals which are 99.99% pure would seem to be homogeneous by definition at any scale.  As for sulfides, I have very little experience with natural sulfides, but again, if a synthetic pyrite (not pyrrhotite), is 99.99% pure, how exactly would it be inhomogeneous? 

Incidentally, a long time ago at UC Berkeley I once characterized a half dozen natural well crystallized pyrite cubes (I might still have the mount) and they had identical Fe:S ratios within precision, so that is hopeful at least. But of course any assumed stoichiometries will have to be evaluated on a case by case basis for any proposed synthetic standards.

If you're thinking of trace elements that is something we will investigate of course, but this project is focused on major elements as that is a large source of analytical error today.  But remember, for SEM and even EPMA, anything below say a few PPM is essentially a homogeneous zero.

Just as an aside, in EPMA the best primary standard for a trace element is the pure metal or pure oxide, and the best secondary standard (again for a trace element) is a (roughly) matrix matched zero blank. Then one can determine ones accuracy at zero concentration since it is the background determination that dominates accuracy for trace elements in EPMA. In fact, the use of a zero blank in EPMA is a gift from the science gods as it is one of the few times that one can obtain accuracy equal to ones measurement precision (Donovan et al., 2011).

So it should be noted (as discussed in the open letter) that these proposed high purity synthetic mineral standards can be utilized as not only primary standards, but also as secondary standards. In fact, one additional aspect of this global effort is the compilation of a "k-ratio consensus database" that can be utilized for testing not only our matrix correction physics, but also our instrument calibrations. Hence the necessity of having at least two materials for every element.

And not only standards for blank measurements but also standards for MAN background calibration curves (Donovan et al., 2017). And I'm sure others can think of other uses for high purity stoichiometric synthetic oxides, silicates and sulfides available globally in significant quantities.

Quote from: jon_wade on November 19, 2021, 02:26:41 PM
Secondly, I'm not sure the inclusion of lab comparisons for the CPX barometry is actually that helpful to the cause. You could also include redox sensors in this, but the problems are more protracted as a critic/reviewer may want to look at the accuracy of the experimental data and point an initial finger there, rather than, say,  just the lack of standards.For instance, what is the true error on Pressure and temperature in the experiments how much does grain size in the natural samples/volatile content/prep play a role etc etc.  In reality a single reference secondary standard would provide intra-lab/run consistency and it doesn't really have to be that 'good'. Many groups already offer their published materials as 'standards', such as Mossbauered synthetic spinels or oxygen bearing sulphides.  Yes, they may not always be that great, but they do provide a common reference point and their availability is often key to publication.

Well I think you just identified the problem!   :P

Yes, the cpx barometry is just one example shared with us by a geologist (Wieser) who approached us about the issue of inter-laboratory bias, which is apparently of some concern in her field. The question of standard accuracy is of course just one concern of many, but given the well documented problems with many standards utilized by these researchers (e.g., Kakanui augite), it seems reasonable to pursue better and more available standards which can be reproduced relatively easily as needed in the future, rather than the "historical accidents" with which we are limited to today. That is to say, we will never get more of the heterogeneous, inclusion ridden Kakanui augite standard, and for that we should all be grateful I say!   :)

I'll let you geologists discuss the other experimental issues you mention, but this project can help by at least getting us all "on the same page" with regards to our primary standards. As mentioned in the open letter, the situation today in microanalysis is a bit like 400 years ago before the introduction of the global metric system.  But this can be remedied and this project is an effort to begin this process.

Quote from: jon_wade on November 19, 2021, 02:26:41 PM
finally - why crystals?  why not glasses?  why the extra effort to synthesise a  crystal that will often require a flux?

We have nothing against glass standards. As discussed in the open letter we do propose utilizing glass standards where they are available in significant quantities and accurately characterized. Ah, but there's the rub. It's not easy to characterize the major elements of a glass composition. Which technique do you trust for this characterization?  As Ben Hansen at Corning Glass said to me recently: who knows what the actual composition of these glasses are? Corning has made a historical decision to rely on XRF calibration curves which I assume relates back to the wet chemistry (gravimetric analysis) of "standard" glasses, but even wet chemistry has its systematic biases.

The other issue with glass standards is that even the NIST K-411 and K-412 glasses are also, when you think about it, just "historical accidents" that will never be exactly reproduced in the future. And there are no more of these materials available today. This is not an ideal situation for long term global standardization.

That said, in my lab when we run say, Mg Ka on synthetic MgO and synthetic Mg2SiO4 against the NIST K-411 and K-412 and BIR-G glasses, we obtain results that agree within precision. Of course this requires that one's dead time constants are precisely calibrated, but it is a sign of hope.

Quote from: jon_wade on November 19, 2021, 02:26:41 PM
and why the amount? is there really a need for kg's of sample which will inherently present more issues of homogeneity when a few grams will keep us happy?  they are, after all, micro analytical standards. ;)

Well for one, we are thinking long term: generations of microanalysts. Second we are thinking of making sure that every microanalytical lab in the world has access to these materials. And third we are hoping that each of these labs has sufficient material to withstand repeated re-polishing and re-coating (and sometimes re-mounting) as is often necessary (our lab re-polishes and re-coats our standard mounts every one to two years).

A quick calculation: let's say there are several hundred EPMA instruments in the world, several thousand SEMs and how ever many other instruments that might benefit from global standards, and let's say we distribute 0.25 or 0.5 grams to each lab (as opposed to the usual "fly specks"). Well we can quickly see that quantities of 500 to 1000 grams are pretty reasonable.

I guess the point being, we can do this, we have the resources, and we (more than 90 co-signers) think we should do this. Will you join us?

But again- it's voluntary.

High purity and high quality synthetic substances... Where should I sign?   8)

I want to point also to few addition small issues and features, which planning of these synthetics IMHO should take into consideration.

1. under-beam stability. Synthetic, but beam-unstable substance will fail miserably as inter-institutional standardization will highly depend from analyst skills/experience on instrument to mitigate those effects. In such case not so pure - but stable minerals would give better inter-lab standardized results. Thus said, I am sceptical about proposed ThSiO4 which is beam unstable, why not simple ThO2? Same for U - UO2 (using depleted U) is what I really recommend. However, for U and Th synthetic minerals there could be problem with distribution in some countries, which have stellar-magnitude-paranoia on that point. Labs  in these countries are doomed to be able to use only low concentration poor-quality glass'es (Last time hear story from some Asian country, It needs to be confirmed). Also we need something stable for Na - which can be challenging to find. So even if We would use such unstable minerals as secondary standards - the goal of getting universal k-ratios would stand on skill and experience of analyst. Another concern for obtaining universal k-ratios is that some biases can be introduced by poor-designed dead-time correction (especially on WDS systems of Jeol and Cameca, where is no pile-up correction).

2. For EDS (especially in case of DTSA-II and NeXL library) it is good to have standard reference material where given peaks are away from other element peaks, so that they could be used as reference (shape) peaks. Thus said, proposed LaAlO3 is poor standard in that case as resolving M lines of La would be possible only by de-convolution, but physical models ...grrr... ignores existence of LREE Ma lines - which produces rubbish deconvolution. Why not use widely available LaB6? The same for other LREE and MREE elements: CeB6, PrB6, NdB6, SmB6, EuB6, GdB6?  These are more and more produced are very beam stable (primary use as cathode, much higher temperatures than what we can get with beam-iradiation). I think from Tb toward Lu it could be oxides or fluorides, but substances should not contain Al or Si as that would complicate M line resolution (deconvolution). Of course these could be said to be the concern of EDS (DTSA-II, NeXL and not PfS concern) and thus is out of scope of this initiative, as PfS can do interference correction on standard (I guess) and WDS in many cases has enough resolution to not get these interferences. However, ignoring these points makes this initiative less universal and more PfS oriented then.

3. Sulfides. Again it is not enough to have only pure standards produced, as most of them degrade. To do the right analyses of sulphides is really a huge challenge - Samples (and reference samples for standardization) needs to be re-polished before to get away the oxidated layer. The handling of sample during and between re-polishing-drying-re-coating-placing-into-chamber will have much more bigger impact than homogeneity of the sulphide reference (I don't recall I ever saw non-homogeneous sulfide standard). Pyrite as a standard is really very very bad chose.

4. I also can't understand why we need 1 kg lump of standard. If there is known process how to do very clean crystallization, why can't it be then multitude of small pieces - which is easier to produce on demand and less waste when dividing. Lets say we get 1 Kg of X mineral. How it will be divided into thousand of pieces? Sawing it (mechanically or with laser) will produce lots of waste. Crushing also would produce some powder - it is not possible to divide without any waste. Producing thousand of small pieces is more efficient, as then there is no need to divide this huge lumps. This point can be completely irrelevant for say synth-wollastonite, but Would generate additional high cost for lets say REE minerals.

So I am all in for this initiative, but not for global reasons (k-ratio DB), which this would be only a small step-toward (but not sufficient on its own), but for more excellent standards available for me, and Now. We are already late, we need these standards yesterday, not for future generations (technology improves, possibly future generations will have much easier means to analyse and synthesize the minerals, it is very probably that no-one would even appreciate this initiative as it could get irrelevant in the future). Every day we use those not-perfect natural minerals as references, and publish such data – we weave this imperfection into whole global scientific fabric. It is very often that even if we update the data in further publications, no-one cares about it at all, the initial values already are circulated, compared against, migrated to some process modelling (and progress these imperfections further and further, which IMHO is near impossible to stop by any erratas or addendum). From other side we need to do analysis to keep the labs running, we can't just stop everything and say we are waiting for a full set of excellent reference materials covering (near-)whole element table. 

P.S. We prefare synth as reference, if available for given element and ox state. But we never use then blindly, all our reference materials are internally checked for homogeneity and trace amount of contaminants (mostly by High Current, full extent, extended-time wavescans). In our lab, only about ~60-70% of bought reference substances can be said that are in agreement to the declared purity and composition. The resolution of issues with standards is actually what discriminate good lab from inferior lab, which blindly believes in ISO's and certificates. And that brings me to this economical, management, political problems:

5. Price and ISO certificate. The biggest, and largest impact on global correctness of analysis could be achieved for new labs, which are going to search for obtaining standards. Unfortunately, most of labs will look to price and available certificates (so that lab could be accredited). Lots of already established SEM labs are not going to be interested, because why? They already have ISO certificated standards, why they should invest in another standards? It is going to be pain to make majority of SEM labs to make any investment in this. (Just think how in the first place it is hard to turn the industry/ EDS vendors away from standartless-EDS analyses). How this initiative is going to deal with concurrency of well established biggest suppliers (SPI, MAC...)? - This leads to very important issue: Do we really need to over-invest in kg scale standards? That implies it should be cheaper than what SPI and MAC and etc... provides, It should also have ISO certificates (which again are additional cost). And even then, Simple-manged SEM lab is more keen to buy the set of standards (like 50 different pieces factory-mounted in copper 1-inch round mount), than to buy separate bulk standards and do its own mounts. Us, EPMA probers are minority in the industry and scientific institutions, I have really huge doubt if this kg scale is not huge exaggeration which will fire-back on the price for us, who are the most interested in this initiative (and i.e. I am not interested in very lax ISO certificates, neither I would be interested for additional charged for that orders-of-magnitude less strict from our internal protocols rubbish (ISO compliance)). Would it be possible to cooperate with SPI, MAC and other big vendors so that they would sell this, and throw out half of the rubbish they sell now?

my comments re: sulfides and metal was really focused on trace elements in standards.  These are rarely homogenous, but there is a desperate need for such in the LA-ICPMS community (et al) where matrix matching is a bigger issue.  Of course, 'pure' standards' should be pure - stands to reason, which is why I favour a good metals block over some of our 'pure' synthetic stuff (MgO is a good example of a commercially available single crystal that we've found is often not as 'pure' as all that).  Sulfides are a particular problem as noted above, and I would be pleasantly surprised if you can make a significant amount that are both 'pure' and stoichiometrically identical. 

I  think a lot could be done to educate current probe users about the role of standard (ahem, SJIO), background selection and instrument operating conditions which would go someway to mitigating a lot of issues (honestly, theres still papers published where dead times in olivine are hit. worrying about your standard is a little moot when that happens!).  I honestly feel the cost/benefits of this mammoth effort isn't there without embracing other microanalytical communities. Perhaps it would be worth doing a thorough market survey of demand (and not just 'I'd like some!' but 'how much would you like some?').  It may also be instructive as my gut feeling is the EPMA community at a research funding level is not in such rude health. :(

The Focused Interest Group on MicroAnalytical Standards (FIGMAS), a FIG of the Microscopy Society of America (MSA) and co-sponsored by the Microanalysis Society (MAS), is organizing a series of round robin exercises to begin investigating synthetic standard materials for developing a universal standards mount and accompanying database of community k-ratios. Details of the round robin and a survey to express interest are included in the link below. All labs who meet the stated criteria are welcome to participate.

https://docs.google.com/forms/d/e/1FAIpQLSd8nttQYcex9UmnHJyD3iHE-vpL7gG5XVpNumX8-fqrWrgb9A/viewform (https://docs.google.com/forms/d/e/1FAIpQLSd8nttQYcex9UmnHJyD3iHE-vpL7gG5XVpNumX8-fqrWrgb9A/viewform)

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
High purity and high quality synthetic substances... Where should I sign?   8)

I want to point also to few addition small issues and features, which planning of these synthetics IMHO should take into consideration.

Great comments. I will respond as best I can below.

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
1. under-beam stability. Synthetic, but beam-unstable substance will fail miserably as inter-institutional standardization will highly depend from analyst skills/experience on instrument to mitigate those effects. In such case not so pure - but stable minerals would give better inter-lab standardized results. Thus said, I am sceptical about proposed ThSiO4 which is beam unstable, why not simple ThO2? Same for U - UO2 (using depleted U) is what I really recommend. However, for U and Th synthetic minerals there could be problem with distribution in some countries, which have stellar-magnitude-paranoia on that point. Labs  in these countries are doomed to be able to use only low concentration poor-quality glass'es (Last time hear story from some Asian country, It needs to be confirmed). Also we need something stable for Na - which can be challenging to find. So even if We would use such unstable minerals as secondary standards - the goal of getting universal k-ratios would stand on skill and experience of analyst. Another concern for obtaining universal k-ratios is that some biases can be introduced by poor-designed dead-time correction (especially on WDS systems of Jeol and Cameca, where is no pile-up correction).

Characterization of beam stability is of course one of our concerns. We propose to carefully characterize all potential candidates for purity, stoichiometry, homogeneity and beam stability as described in the open letter. 

Though I am surprised by your mention of ThSiO4 beam stability as I have both synthetic huttonite and thorite from John Hanchar and both seemed to be quite beam stable, though it has been years since I looked at them. However almost every material is beam unstable at some level given sufficient beam focus and beam currents. I will have to re-examine these materials. That said, ThO2 and UO2 would be excellent standards, though we would prefer at least two materials for each element in order to make k-ratio measurements.

However, I am heartened by my experience of beam stability in many other crystal synthetics, for example RbTiOPO4 as a Rb standard which is wonderfully beam stable. Interestingly there is also a widely available KTiOPO4 synthetic which would be worth testing for K stability. Would anyone be willing to provide us with a few grams for testing?

In the past we have also discussed synthesis of a Cs zircono phosphate material... certainly something like this would be better than the usual "fly specks" of pollucite that are sometimes circulated:

https://smf.probesoftware.com/index.php?topic=560.msg6674#msg6674

As for "universal" or as I call them "consensus" k-ratios, you are correct, this indeed will be a significant amount of work. However, eventually once these materials are properly characterized they could also be used to test instrumental performance, e.g., dead time calibrations, effective take off angles, beam current linearity, etc. not to mention matrix correction models, etc. as described in the open letter.

It must also be pointed out that such "consensus" k-ratio measurements will not be arrived at naively, but rather will be evaluated carefully to obtain to most accurate values possible. In other words if ones WDS detectors are not already carefully calibrated for dead time, ones reported k-ratios will not be helpful. The skill and dedication of the operator will indeed be a critical factor in such measurements.  I can think of a handful of such people that I would immediately trust...

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
2. For EDS (especially in case of DTSA-II and NeXL library) it is good to have standard reference material where given peaks are away from other element peaks, so that they could be used as reference (shape) peaks. Thus said, proposed LaAlO3 is poor standard in that case as resolving M lines of La would be possible only by de-convolution, but physical models ...grrr... ignores existence of LREE Ma lines - which produces rubbish deconvolution. Why not use widely available LaB6? The same for other LREE and MREE elements: CeB6, PrB6, NdB6, SmB6, EuB6, GdB6?  These are more and more produced are very beam stable (primary use as cathode, much higher temperatures than what we can get with beam-iradiation). I think from Tb toward Lu it could be oxides or fluorides, but substances should not contain Al or Si as that would complicate M line resolution (deconvolution). Of course these could be said to be the concern of EDS (DTSA-II, NeXL and not PfS concern) and thus is out of scope of this initiative, as PfS can do interference correction on standard (I guess) and WDS in many cases has enough resolution to not get these interferences. However, ignoring these points makes this initiative less universal and more PfS oriented then.

Good and widely available standards for quant EDS are certainly important as mentioned in the open letter. Your suggestion of REE borides and fluorides is a good idea. Would you be willing to investigate the commercial availability and pricing of such high purity REE borides and fluorides for us? We would be very interested. I know that high purity BaF2 and MgF2 are easily available. But with LaB6 is it high purity?  Please find out for us.

I should emphasize, this global effort has nothing to do with any particular software or vendor. Yes, EDS will struggle with some WDS standards for creating valid profile spectra, but certainly simple synthetics will usually be a better bet than some natural material loaded with various minor elements. LA-ICPMS will also require trace element homogeneity, and that will be another aspect to consider.  But we need to start somewhere and not get overwhelmed by satisfying every possible criteria immediately.

Since EPMA geologists are generally most concerned with major and minor element accuracy, we say let's start with suitable primary and secondary standards for EPMA geology and see what we can obtain.  This of course, is not to exclude any SEM geologists!   :D

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
3. Sulfides. Again it is not enough to have only pure standards produced, as most of them degrade. To do the right analyses of sulphides is really a huge challenge - Samples (and reference samples for standardization) needs to be re-polished before to get away the oxidated layer. The handling of sample during and between re-polishing-drying-re-coating-placing-into-chamber will have much more bigger impact than homogeneity of the sulphide reference (I don't recall I ever saw non-homogeneous sulfide standard). Pyrite as a standard is really very very bad chose.

I'm sure sulfides will be a challenge which is why we have started looking at synthetic oxides and silicates. Sulfides were mentioned in the open letter because some co-signers felt we shouldn't exclude the ore people. If these types of standards are important to your work, perhaps you could help us research commercially available synthetic materials?  Please ask about purity, stoichiometry, pricing and availability. First in amounts of a few grams for initial testing and characterization, but eventually in larger quantities for global distribution.

Curious: why would high purity synthetic pyrite be such a bad standard material? Seems quite stable when I've used it at 30 nA and 20 keV.  Then again I usually run my standards slightly defocused or turn on the TDI correction.

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
4. I also can't understand why we need 1 kg lump of standard. If there is known process how to do very clean crystallization, why can't it be then multitude of small pieces - which is easier to produce on demand and less waste when dividing. Lets say we get 1 Kg of X mineral. How it will be divided into thousand of pieces? Sawing it (mechanically or with laser) will produce lots of waste. Crushing also would produce some powder - it is not possible to divide without any waste. Producing thousand of small pieces is more efficient, as then there is no need to divide this huge lumps. This point can be completely irrelevant for say synth-wollastonite, but Would generate additional high cost for lets say REE minerals.

The eventual need for 500 to 1000 gram quantities is explained in my response to Jon Wade above. As for waste, there will always be some produced, but I'm sure we can minimize that problem. We are already discussing with some vendors that single crystal boules are not necessary, as long as the pieces are at least millimeters in size and crystalline.

It all depends on how the crystal material is produced. If produced as a single boules it will have to be sawn or crushed. This may be unavoidable depending on how it is supplied to us.

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
So I am all in for this initiative, but not for global reasons (k-ratio DB), which this would be only a small step-toward (but not sufficient on its own), but for more excellent standards available for me, and Now. We are already late, we need these standards yesterday, not for future generations (technology improves, possibly future generations will have much easier means to analyse and synthesize the minerals, it is very probably that no-one would even appreciate this initiative as it could get irrelevant in the future). Every day we use those not-perfect natural minerals as references, and publish such data – we weave this imperfection into whole global scientific fabric. It is very often that even if we update the data in further publications, no-one cares about it at all, the initial values already are circulated, compared against, migrated to some process modelling (and progress these imperfections further and further, which IMHO is near impossible to stop by any erratas or addendum). From other side we need to do analysis to keep the labs running, we can't just stop everything and say we are waiting for a full set of excellent reference materials covering (near-)whole element table. 

We all want excellent standards now (or even yesterday would be nice), but most of us live in the real world and know that a scientific project as presented in the open letter requires time, money, cooperation and a lot of effort. I'm sure you agree.

And no one is saying we have to stop all current lab work immediately until this project is complete. Where did you see that mentioned in the open letter?   >:(

Everyone will have their own reasons for joining this project, we hope you will find sufficient reasons of your own to help us in this global effort. It might be one of the most enduring contributions we can make to our field.

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
P.S. We prefare synth as reference, if available for given element and ox state. But we never use then blindly, all our reference materials are internally checked for homogeneity and trace amount of contaminants (mostly by High Current, full extent, extended-time wavescans). In our lab, only about ~60-70% of bought reference substances can be said that are in agreement to the declared purity and composition. The resolution of issues with standards is actually what discriminate good lab from inferior lab, which blindly believes in ISO's and certificates. And that brings me to this economical, management, political problems:

Good for you. I wish all labs worked so diligently on their standard materials.  8)

I am reminded of occasions when I have been contacted by some EPMAers attempting to utilize the MAN background correction (Donovan et al, 2017), and been told that they had no idea that their standards were so contaminated with minor and trace elements...   :(

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
5. Price and ISO certificate. The biggest, and largest impact on global correctness of analysis could be achieved for new labs, which are going to search for obtaining standards. Unfortunately, most of labs will look to price and available certificates (so that lab could be accredited). Lots of already established SEM labs are not going to be interested, because why? They already have ISO certificated standards, why they should invest in another standards? It is going to be pain to make majority of SEM labs to make any investment in this. (Just think how in the first place it is hard to turn the industry/ EDS vendors away from standartless-EDS analyses). How this initiative is going to deal with concurrency of well established biggest suppliers (SPI, MAC...)? - This leads to very important issue: Do we really need to over-invest in kg scale standards? That implies it should be cheaper than what SPI and MAC and etc... provides, It should also have ISO certificates (which again are additional cost). And even then, Simple-manged SEM lab is more keen to buy the set of standards (like 50 different pieces factory-mounted in copper 1-inch round mount), than to buy separate bulk standards and do its own mounts. Us, EPMA probers are minority in the industry and scientific institutions, I have really huge doubt if this kg scale is not huge exaggeration which will fire-back on the price for us, who are the most interested in this initiative (and i.e. I am not interested in very lax ISO certificates, neither I would be interested for additional charged for that orders-of-magnitude less strict from our internal protocols rubbish (ISO compliance)). Would it be possible to cooperate with SPI, MAC and other big vendors so that they would sell this, and throw out half of the rubbish they sell now?

This issue of cost and working with commercial microanalysis providers has been discussed on a number of Zoom calls with many of the co-signers, and we have made a few decisions regarding your points above:

1. These samples will be developed by volunteers in the microanalysis community and any commercially sourced materials will be purchased through grants and matching funds. As mentioned in the open letter several microanalysis societies have more than sufficient funding to get this project well on its way. Several of our members are already beginning the process of grant writing to further extend our purchasing power.

That said. there are possibilities of obtaining synthetic crystal material from state sponsored crystal growing projects which, if located, might be freely available. In addition, some of us have been able to obtain hundreds of grams of various synthetic materials from commercial crystal producers for *free* by asking nicely if they have any scraps or "cutoffs" from their boules!  If you don't ask, you already know the answer!   :)

So the plan is that these materials will be provided for free to qualifying laboratories. A good first step in that qualification process is to join the FIGMAS:

https://figmas.org/about.php

2. In order to provide a long term and stable repository for these synthetic materials, we have been informed that the Smithsonian Institution would be pleased to provide this service for our global standards project, but they cannot have any association with commercial providers that would be making a profit from the sale of these materials.

3. The question of ISO certification is outside my area of expertise, but maybe some else can chime in on this?

Quote2. In order to provide a long term and stable repository for these synthetic materials, we have been informed that the Smithsonian Institution would be pleased to provide this service for our global standards project, but they cannot have any association with commercial providers that would be making a profit from the sale of these materials.

It seems to me that for this to be a success (meaning we actually reach those people tempted to use standards as long as it isn't too hard), we need to involve commercial vendors.  This suggests that, as kind as the Smithsonian's offer is, we should probably look for someone else to handle the material who isn't averse to associating with commercial vendors.

Quote from: jon_wade on November 22, 2021, 08:25:53 AM
my comments re: sulfides and metal was really focused on trace elements in standards.  These are rarely homogenous, but there is a desperate need for such in the LA-ICPMS community (et al) where matrix matching is a bigger issue.  Of course, 'pure' standards' should be pure - stands to reason, which is why I favour a good metals block over some of our 'pure' synthetic stuff (MgO is a good example of a commercially available single crystal that we've found is often not as 'pure' as all that).  Sulfides are a particular problem as noted above, and I would be pleasantly surprised if you can make a significant amount that are both 'pure' and stoichiometrically identical. 

I can imagine that some synthetic materials might be inhomogeneous in trace elements especially at ICPMS sensitivity levels, but if we start with high purity materials we might mitigate much of that, especially for EPMA where anything below a few PPM is essentially undetectable.

As for LA-ICPMS standards I agree metals or oxides would work well as primary standards. Pretty much the same situation in EPMA, though some people still haven't thought this question through sufficiently and are still seeking some trace doped standard to test their trace accuracy. The best accuracy test for trace levels is a zero blank. See here for more details:

https://smf.probesoftware.com/index.php?topic=928.msg8498#msg8498

As for testing trace accuracy in LA-ICPMS, I would similarly ask why not a (roughly) matrix matched (high purity) blank as we are (or should be!) using in EPMA?

As for commercial MgO, today it is quite easy to find MgO with close to zero Ca.  This was not true in the past. Likewise, it used to be almost impossible to find Zr without a percent or so of Hf, but this material is now available in 99.999% pure form:

https://www.americanelements.com/zirconium-metal-7440-67-7

Question: I know nothing about growing synthetic sulfides, but in talking with John Hanchar he has indicated to me that it's the purity of the starting materials that matter (and cost) the most!

Quote from: jon_wade on November 22, 2021, 08:25:53 AM
I  think a lot could be done to educate current probe users about the role of standard (ahem, SJIO), background selection and instrument operating conditions which would go someway to mitigating a lot of issues (honestly, theres still papers published where dead times in olivine are hit. worrying about your standard is a little moot when that happens!).  I honestly feel the cost/benefits of this mammoth effort isn't there without embracing other microanalytical communities. Perhaps it would be worth doing a thorough market survey of demand (and not just 'I'd like some!' but 'how much would you like some?').  It may also be instructive as my gut feeling is the EPMA community at a research funding level is not in such rude health. :(

I agree that for many laboratories the dead time calibrations are probably a major area of inaccuracy. Paul Carpenter has tried to point this out for decades. If anyone out there is still using the "default" dead time calibrations provided to them at the time their instrument was installed, I can promise them that they have large accuracy problems. These gas detectors age quite dramatically over time and one should be re-running these dead time calibrations every year to two at most for reasonable accuracy.  This issue has actually gotten worse over time as both Cameca and JEOL have migrated to larger and larger Bragg crystals with increasing geometric efficiency.

So unless you always run a 10 nA or less, here is a link to Paul Carpenter's dead time spreadsheet which is very nice for performing your own dead time constant calculations using any software:

https://smf.probesoftware.com/index.php?topic=1160.0

As for other microanalysis communities, we welcome all. I note that Zack Gainsforth at UC Space Sciences just wrote to Will Nachlas volunteering his TEM time, would you be willing to work with us on laser ablation standard characterization?

We need all the help we can get.

Quote from: NicholasRitchie on November 22, 2021, 12:21:57 PM

Quote2. In order to provide a long term and stable repository for these synthetic materials, we have been informed that the Smithsonian Institution would be pleased to provide this service for our global standards project, but they cannot have any association with commercial providers that would be making a profit from the sale of these materials.

It seems to me that for this to be a success (meaning we actually reach those people tempted to use standards as long as it isn't too hard), we need to involve commercial vendors.  This suggests that, as kind as the Smithsonian's offer is, we should probably look for someone else to handle the material who isn't averse to associating with commercial vendors.

Really?  I'm not opposed to having this global material hosted in several locations, but it's not just the Smithsonian, it's also NSF. I'm pretty sure NSF would not fund an effort that involves for profit activity.

Maybe once we've got a stable of high purity global standards that have been shared with the labs that actually care about accuracy, then we can have discussions with commercial providers.

While discussing WDS detector dead time calibration issues someone recently made the following point which I'd like share here:

QuoteFrom my perspective it's exactly these sorts of instrumental calibration issues that has over time tended to corral people into finding matrix matched standards even as the matrix corrections themselves have become more accurate. As has been pointed out previously, if ones standard is exactly the same composition as ones unknown, *all* corrections are exactly 1.000!

So I think that what started out as a necessity for dealing with sub par matrix correction physics, has over the decades slowly become a crutch to avoid making sure our instruments are properly calibrated in other respects (dead time, effective takeoff, beam current linearity, etc.).

The good news is that by utilizing standards that are not exactly matrix matched, but instead accurately characterized for composition and purity, these instrumental calibration issues (and matrix correction physics) will become better understood and therefore more easily able to be improved.

Quote from: Probeman on November 22, 2021, 10:35:08 AM
I know that high purity BaF2 and MgF2 are easily available. But with LaB6 is it high purity?  Please find out for us.

BaF2 and MgF2 are not so good EDS standards for the same reasons as La oxide-bearing phases (The Ba can emit Ma, especially if working with low voltages). Sincerely, I currently have no Ba standard which would allow to deal with this problem. One of candidates I would look for is Ba carbide (BaC2, https://www.americanelements.com/barium-carbide-50813-65-5), the same for Cs (Cs2C2) - I however have no idea how stable those would be. Currently to overcome these shortcomings I set DTSA-II to ignore M lines of Ba, but for any low voltage work that will bring huge impact on F and O EDS direct quantization.
As far of concerning LaB6 purity it needs to be pure as that is main material of that type of cathodes - any contaminants would cripple the stable emission. As from EPMA WDS perspective - I have wavescans and it is pure from that point of view.

Now When I say "wavescans" I mean very high current wavescans acquired using all available electron juice on our field emission SXFiveFE. Normally that is around 800nA and more (up to 1µA) which makes tops of peaks to blunt (unaccounted pile-up), but it exposes the backgrounds very clearly and any spectral artifacts or impurities at 10-50 ppm level is visible (depends from position and XTAL, (2048 channels 1 second per channel). The beam is defocused to 50um. The carbon coat is done with Leica coater with multi-pulse mode which makes a composite carbon layer which allows the coating to withstand 40+ minutes at these harsh conditions easily for most of standards. (Coating - this is again one of these underrated very crucial steps which if done wrongly will ruin analysis). Exception is minerals which breaks down (i.e. apatite) at this beam. I actually more believe my wavescans than some LA-ICP-MS where I have no control on fractionation, data reduction, laser stability. Lots of stuff there (at least what I had witnessed with my limited experience there) is quite a black box. And LA-ICP-MS can have all kind of nasty interference (mass interference). What I would be interested more for low concentration detection is µXRF. Don't understand me wrong, LA-ICP-MS is really robust method for comparative analysis (REE spider plot patterns, Isotope ratios, etc..), but I had never ever seen a reliable results for absolute values which would sum to 100 % (rather very far from it). Maybe there will be difference with new generation femto-second lasers, but previous generation with all that fractionation stuff is very unreliable as for absolute values, and I would take EPMA or µXRF (if done correctly) values without any doubt if would need to chose from values obtained by different methods. In that sense EPMA-WDS wavescan is quite a powerful and more reliable tool IMHO for trace detection down to tens of ppm especially when there is no interference hell (standards) and interpretation of such wavescan is simple.

Getting back on topic, as For EPMA-WDS REE I see no need of those REE borates, as REEPO4 scratch my all possible itches. (and there are also those REEP4O14, which I find less stable than REEPO4, and use it not at all). I don't know where we got these REEPO4 as they show absolutely no wavescan-detectable Pb (unfortunately, there is a very sad story behind that, why I don't know where it comes from). REE-borates would be handy for low voltage EDS, or/and substances where F, O, Na needs to be measured directly. 

Quote from: Probeman on November 22, 2021, 10:35:08 AM
Curious: why would high purity synthetic pyrite be such a bad standard material? Seems quite stable when I've used it at 30 nA and 20 keV.  Then again I usually run my standards slightly defocused or turn on the TDI correction.

Let me put Your another quote below from your previous post:

Quote from: Probeman
(our lab re-polishes and re-coats our standard mounts every one to two years)

If Your unknown pyrites was re-polished some weeks before EPMA session, then both your standard and Unknown pyrites are oxidized. You get away from it with 20kV generating X-rays from deeper of sample (for that reason alone I do all sulphides at 25kV). You will notice, however, that same calibrations does not give good result for chalkopyrite (even with corrected S position). That is as chalkopyrite oxidizes at different rate and extent. So basically, while your Unknown will be similarly oxidised as your standards you will get away with it, But try to do freshly polished Unknown samples and you should get some surprise.

How we do sulphides? as for sulphur reference we use ZnS which does not oxidizes, and does not require to be often re-polished (we re-polish our standards as You do - once a year). We don't use neither pyrite neither chalkopyrite standards as the only good correct analysis (intensity) possible to obtain from them is at first days after re-polishing of standard block. Samples of Unknown needs to be polished a day (for best results) before session. Differently than other samples, sulphide (for analysis) bearing samples are not placed into heater for riddance of water vapour, as oxidation of pyrite/chalkopyrite and other sulphides increase with temperature. We dry samples with stream of nitrogen gas, and then keep it longer in coater in vacuum to get away the vapour residual (like 1-2 hours). After coating it should not lay days on shelf (or worse in the heater) as coating is not enough to prevent pyrite from oxidation. The best it should be analysed the same day. We use Fe,Co, Ni, Cu and other metals from normal oxide standards like Fe2O3, CoO, NiO... or metals (i.e. Ag, Au) and sulphur only from ZnS. Analysis in this way closes around 100%, and most importantly the atomic composition makes complete sens. If we would try to repeat analysis after a week, there would be huge discrepancies.

Quote from: Probeman

Quote from: sem-geologist on November 22, 2021, 03:33:06 AM
From other side we need to do analysis to keep the labs running, we can't just stop everything and say we are waiting for a full set of excellent reference materials covering (near-)whole element table. 

And no one is saying we have to stop all current lab work immediately until this project is complete. Where did you see that mentioned in the open letter?   >:(

These are inner personal regrets sometimes. Especially when looking to some mine, one of the first analysis which were published. At least I find myself pretty often in situation when I am asked for results immediately! Even if there are some clear analytical biases or artifacts (which were not obvious previously), which would imply to redo some analysis at changed settings. Not everyone would say "Ok, take time and investigate and make sure these next analyses are correct, or redo those and make it more correct", rather "We already published this paper with these standards and these settings, we don't want to describe new methodology, we just will cite that old one, we don't ***** care... it should be completely the same. Period!", because our system is publish-or-perish, and incremental improvement of method does not fit well with that system.

So that is why I wish to have synth's covering all elements already yesterday. Of course I understand that it will take time.

Quote from: Probeman
I am reminded of occasions when I have been contacted by some EPMAers attempting to utilize the MAN background correction (Donovan et al, 2017), and been told that they had no idea that their standards were so contaminated with minor and trace elements...   :(

That is why I don't use MAN, but single background and precise and universal slope - This way I can get down to 10 ppm, but without: any hassle of LA-ICP-MS of standards, making background correction curves, etc. Simple, elegant, reliable, works same independently from matrix.

Quote from: Probeman
So the plan is that these materials will be provided for free to qualifying laboratories. A good first step in that qualification process is to join the FIGMAS:

https://figmas.org/about.php

Do I understand correct, I should join at first MicroAnalysis Society (MSA, as European joining MAS would make little sense), then I  should join FIGMAS?

As dead time was picked few times... I probably should get back and finish my MC simulation of pile-ups and come up at last with non-linear equation which actually works for whole range of possible count rates (0-1Mcps), and different generation of counting electronics.

If anyone is interested in our current Google spreadsheet of commercially available synthetic standard material candidates, as shown here:

(https://smf.probesoftware.com/gallery/395_23_11_21_11_49_22.png)

Please use this link:

https://docs.google.com/spreadsheets/d/19AeXvxIaP6qvChbE7cxK05B_6rkZSN14T-7ZJ7nkm8M/edit*gid=0 (https://docs.google.com/spreadsheets/d/19AeXvxIaP6qvChbE7cxK05B_6rkZSN14T-7ZJ7nkm8M/edit*gid=0)

If you would like to add to this spreadsheet any additional commercial (or academic or institutional) sources of potential synthetic standard candidates, please contact Nicholas Ritchie and he can add your email to the approved  "edit list".  Please read the instructions carefully so this spreadsheet remains well  organized.

Ultimately we are looking for high purity synthetic materials in 500 to 1000 gram quantities, enough for true global standards with extra material for future generations. This material does *not* need to be crystallographically oriented or polished. Also these do not need to be single crystals, they can be broken in pieces as long as the individual crystals are at least millimeter(s) in size.

We're looking for: Mg2SiO4, YAG, RbTiOPO4, KTiPO4, MnO, Fe3O4, NiO, ZnO, LaAlO3, MnPSe3, LiTaO3, ZrSiO4 (zircon), ZrO2 (zirconia), HfSiO4 (hafnon), HfO2 (hafnia), ThSiO4 (tetragonal thorite), ThSiO4 (monoclinic huttonite), Fe2SiO4 (fayalite), Mn2SiO4 (tephroite), CaMgSi2O6 (diopside), Al2SiO5 (sillimanite), NaAlSiO4 (nepheline), KAlSi3O8 (sanidine), KAlSi2O6 (leucite), KAlSi3O8 (orthoclase), NaAlSi3O8 (albite), CaAl2Si2O8 (anorthite), Fe3Al2Si3O12 (almandine), PbSiO3 (alamosite), CaAl2O4 (krotite), CaAl4O7 (grossite), CaAl12O19 (hibonite), CaSiO3 (wollastonite), MgSiO3 (enstatite), FeSiO3 (ferrosilite), sulphides and sulfosalts, etc., etc.

We would like pricing on 500 to 1000 gram amounts and also, for some initial testing, pricing on amounts in the range of 3 to 5 grams.

We need your help in tracking down suitable materials! 

FIRM WRITTEN price quotes are the first step.

Note added next day:  Also required would be the minimum order whether in kilos or $$$.

The "cost to synthesize" does not include the cost of raw materials.  Hf-free Zr will cost a lot more than natural Zr.  Then  there is the cost of making ZrO2 powder, then the recrystallizatio

ZrO2 is usually stabilized with Y2O3: better make sure your spec is precise.  You may not have an option if the transition from low symmetry to cubic is below the melting point.  Charles Taylor had natural ZrO2 with 0, 5%, 10%, 15% and 20% Y2O3.  Below 15% Y2O3 the pieces were crappy polycrystalline dust.   But who knows where all that got to?

One  reason to avoid LaB6, CeB6 etc is the extremely high melting point.  Materials are usually sintered--pressed in a furnace but not melted.   Commercial RSi2 is a mix of R rich and Si rich phases , each phase about 1 micron across.

Excellent advice.

Would you be able to help us locate some high purity ZrO2? And also perhaps some single crystal borides?  We only need a few grams to start our initial testing of purity and stoichiometry. Later we will want quotations for 500 to 1000 grams.

If you know of specific sources we would love to hear from you. This is a crowd sourced project, if we don't do it, no one else will.

Please send any written quotes to Will Nachlas:

Will Nachlas
Weeks Hall for Geological Sciences
1215 West Dayton St
Madison WI 53706

Will Nachlas <nachlas@wisc.edu>

or add the quotation information to our Google spreadsheet:

https://docs.google.com/spreadsheets/d/19AeXvxIaP6qvChbE7cxK05B_6rkZSN14T-7ZJ7nkm8M/edit*gid=0

We need all the help we can get, thank-you!

I have a lead on potential sources for ZrO2 and YAG (Y3Al5O12). Does anyone have experience with materials from the Shelby Gem Factory? They were a world renowned synthesizer of several gemstones and apparently invented a technique for synthesis of CZ (ZrO2) using the Czochralski method. The factory closed in 2019 and all of the remaining stock was sold in bulk. I met a local gem dealer who claims to have obtained "hundreds" of pounds of bulk gemstones from the owner when it closed. I purchased ~7 g pieces of colorless ZrO2 and YAG. I will mount and test them for crystallinity and trace impurities to evaluate if materials from the Shelby factory could be suitable for our purposes.

Quote from: crystalgrower on November 26, 2021, 02:11:10 PM
One  reason to avoid LaB6, CeB6 etc is the extremely high melting point.  Materials are usually sintered--pressed in a furnace but not melted.   Commercial RSi2 is a mix of R rich and Si rich phases , each phase about 1 micron across.

The high melting point was actually my main Pros to propose these REEB6, as that would be outstandingly stable under the electron beam. However, after doing more research on hexaboron structure, I came to see a much bigger problem for this material to be considered as standards.
I was trying to understand what oxidation state Ce inside CeB6 would be presented (generally REEB6, with REE as +2/+3/+4 and B +3/-5, looks not straight forward to understand). The structure of REEB6 can be described as B cage (B octhahedras connected in cubic fashion providing cells in between for REE) with entrapped REE in formed cells. Ideally stochiometric LaB6 (deep violet) is then all cells are occupied. But there can be vacancies, some sources suggest that in some extreme cases it can be 1/4 of cells not occupied by REE. Generally, it is easy to get slightly out of stochiometry values, and it is not so straight forward to check how much vacancies are there, without relying on other methods. The LaB6 which I have in one of SPI sets, and which looks very clean and homogenos, is clearly out from ideal stochiometry/has vacancies (phew, I at last have an explanation why it would give so systematically slightly different result compared with LaPO4 as standard). So REE-hexaborons are out from considerations. (They would still be excellent beam-shape standards for low voltage EDS, but should not be used as primary standards)

Quote from: Probeman on November 22, 2021, 12:32:26 PM
...dead time calibrations are probably a major area of inaccuracy. Paul Carpenter has tried to point this out for decades. If anyone out there is still using the "default" dead time calibrations provided to them at the time their instrument was installed, I can promise them that they have large accuracy problems. These gas detectors age quite dramatically over time and one should be re-running these dead time calibrations every year to two at most for reasonable accuracy.  This issue has actually gotten worse over time as both Cameca and JEOL have migrated to larger and larger Bragg crystals with increasing geometric efficiency.

So unless you always run a 10 nA or less, here is a link to Paul Carpenter's dead time spreadsheet which is very nice for performing your own dead time constant calculations using any software:

https://smf.probesoftware.com/index.php?topic=1160.0

It should be emphasized that utilizing standards that are not exactly matrix matched, will result in accuracy errors if ones instrument is not properly calibrated. Paul Carpenter and John Fournelle and been consistently making this point for decades, and before them it was Dan Weill and John Armstrong...  when will we ever learn?

To make this point clearer, I am attaching an abstract and presentation by Paul and John (but not George and Ringo!), from about 15 years ago.

Unfortunately I don't think things have gotten any better on this front since then.  The good news is that the synthetic high accuracy high purity minerals that are being proposed in the topic will help reveal to what extent our instrument require proper re-calibration of detector dead times, PHA settings, effective takeoff, etc., etc.

One possibility for evaluating the synthetic crystals for stoichiometry under consideration for this endeavor is X-ray synchrotron diffraction imaging. I have never performed such a measurement, but imagine there are a number of beam lines that could be used to determine the distribution of defects/inclusions in a multi-mm cm?-sized crystal to verify the structure on a spatially resolved basis. 

I will not comment on the ZrO2 because it belongs in a separate topic.

There is absolutely no reason for individuals to go and get price quotes because they will not be valid for the body that would be making the purchase according to the plan in the first post. 

Individuals are NOT representatives of the money holding body for the purpose of signing contracts for custom syntheses or purchases.

In any case the price quotes will probably expire  before any formal agreement to spend funds will be reached.

Lab managers who purchase supplies and sometimes instruments should be familiar with the process of funds being approved.  I don;t know how any professional could get an idea that crowdsourcing tactics are going to collect  any valid information towards  a corporate purchase. 

And since you haven't been placing orders for custom materials, please be aware that a sample is not released  until a contract is signed.  A significant part of the total price is required to be paid before ANY work of synthesis begins.

Quote from: crystalgrower on December 13, 2021, 12:51:53 PM
I will not comment on the ZrO2 because it belongs in a separate topic.

There is absolutely no reason for individuals to go and get price quotes because they will not be valid for the body that would be making the purchase according to the plan in the first post. 

Individuals are NOT representatives of the money holding body for the purpose of signing contracts for custom syntheses or purchases.

In any case the price quotes will probably expire  before any formal agreement to spend funds will be reached.

Lab managers who purchase supplies and sometimes instruments should be familiar with the process of funds being approved.  I don;t know how any professional could get an idea that crowdsourcing tactics are going to collect  any valid information towards  a corporate purchase. 

And since you haven't been placing orders for custom materials, please be aware that a sample is not released  until a contract is signed.  A significant part of the total price is required to be paid before ANY work of synthesis begins.

I adamantly disagree. The vendor information, availability and (rough) pricing is still valuable information for eventual group purchases.  Remember, we need to purchase small amounts initially to test for purity and stoichiometry.

Even more to the point, we are asking our community to investigate *all* possible sources for these materials, not only commercial sources but also state/government laboratories that may be able to offer our community such materials for *free*.  If we do the leg work.  You can decide for yourself if you would like to join this effort (or not).  :)

I am attaching below (login to see attachments) documents from the global synthetic microanalysis standard project (unofficial):

1. Action plan

These are just draft ideas for how to proceed with this project. Will Nachlas is already moving ahead on a number of these steps and I hope you will participate. Check with the protocols he has specified including making careful instrument calibrations prior to any measurements, especially dead time calibrations on your WDS spectrometers.

2. Resources

Possible resources for obtaining high purity synthetic minerals, though we need your help to find/locate more materials and obtain rough pricing.

3. George Rossman's personal synthetic crystal collection (Cal Tech).

This is a spreadsheet from George Rossman showing what synthetic minerals have been produced in the past, as a guide to what *might* be possible to produce on larger scales for use as global microanalysis standards.

Under the original heading of sourcing  high quality materials:
I  learned a very different way of business with ACS and Mineralogical Society of America.

US Professional associations can incorporate as nonprofits for  their educational activities.  I have not checked to see if either MAS or Microscopy  Society of America have done this.
The benefit of having approval from a nonprofit to solicit donations of materials is that you may be able to solicit a much larger donation in return for a tax receipt.  Which tax receipt can only be issued by the financial officer of the association and their 503(b) registration number must appear. 
In fact a custom synthesis will never be donated without  100% of fair market  value including the cost of starting materials becoming a tax benefit.

Good Biz 101 is  not difficult or obscure. 
I have a specific concern.  The drive to  lowball legitimate businesses started with the forum survey asking users what they would like to pay as opposed to teaching them what it costs to make specialty pure materials.  Now users are being asked to carry out fishing   expeditions.   Should many users  falsely state they represent the MAS then the blowback might be worse than just denial of funds. 

The real intent of this Open Letter may be  to acquire some piles of materials not able to be sold for other reasons.   A pitch to ask for business leftovers  should have been stated up front, rather than all the noise about money possibly  sitting in the bank accounts of nonprofits. 
FYI: all those  pieces that SPI advertises are owned by Astimex Standards registered in Canada (no US tax benefit for donation) and the physical location might be a problem.

Users had better think very carefully where lowlballing small industry might lead.  About 10  years ago I found a small US company with SBIR grand funds, whose business was hydrothermal-grown  crystals of pure and layered materials.  They did not hand out free samples when asked.  They would have been the ideal place to commission Pb-free replacements for RPO4 of R=La-Gd (since all crucible fluxed methods leave contamination).  That commission could then have been donated to the NMNH as Lynn Boatner did with the original TVA materials.  But they  closed sometime before 2017. 

Quote from: crystalgrower on December 17, 2021, 11:41:22 AM
The real intent of this Open Letter may be  to acquire some piles of materials not able to be sold for other reasons.   A pitch to ask for business leftovers  should have been stated up front, rather than all the noise about money possibly  sitting in the bank accounts of nonprofits. 

Asking for commercial quotations, seeking state/government sources, asking for "leftovers" and custom synthesis are all activities that can be pursued in parallel, they are not exclusive pursuits.

Nachlas et al. are currently writing grant proposals, and matching funds may be required from "money in bank accounts of non profits", though exactly how that will be leveraged is up to those society directors.

There has been some discussion in this topic on whether we really require so called "matrix-matched" primary standards for high accuracy EPMA. That is, do our primary standards really need to be similar in composition (and also valence and coordination), to our unknown materials?

So aside from the questions regarding the accuracy of our compositional matrix correction physics, it's a valid question since as we know from multiple studies that in the case of light elements at least, we experience peak shift and shape effects that can result in accuracy problems when not utilizing integrated area scan acquisitions for elements such as oxygen, nitrogen, carbon, boron, etc. Even sulfur k-alpha can have a significant peak position shift (though not a shape change) depending on the oxidation state of the sulfur:

https://smf.probesoftware.com/index.php?topic=127.0

So, even if our compositional matrix corrections were perfect, we would still need to ascertain the magnitude of the peak shift and shape effects due to chemical states. And I think it's still an open question whether we can accurately extrapolate from one material to another when the element (mission transitioning from the valence shell) in our primary standard is in a difference valance state and/or coordination than that of our unknown.

And that is one reason why we selected as our first test sample for the high purity synthetic standard round robin three materials: MgO, Al2O3 and spinel (MgAl2O5). The idea being that these pairs (Mg Ka in MgO to MgAl2O3 and Al Ka in Al2O3 to MgAl2O5), are not only very different in composition, but also somewhat different in their chemical states.  And those materials were readily available as high purity synthetics!  :)

We are still awaiting the results from this first round robin, but I decided to share another test of this concern, that is Si Ka in SiO2 compared to some common silicates.  This was a test I ran recently looking further into the problem of measuring trace Sr and Rb in silicates, but let's ignore those trace results for now and focus on the Si and Al major elements. Unfortunately I didn't have an Al2O3 standard in the standard mount (and wasn't running this test for the Si and Al concentrations as they were only being measured for the interference corrections), but still the Si data might be helpful regarding these major elements accuracy issues.

So using SiO2 as the primary standard for Si (and nepheline as the primary standard for Al), we obtain these results for labradorite:

ELEM:      Sr      Rb      Si      Al      Ca      Na      K      Fe      Mg      O  SUM  
  1379    .055  -.013  24.495  16.458  9.577  2.841    .100    .319    .084  46.823 100.739
  1380    .051  -.001  24.060  16.495  9.577  2.841    .100    .319    .084  46.823 100.350
  1381    .061  -.004  24.038  16.513  9.577  2.841    .100    .319    .084  46.823 100.351
  1382    .070  -.016  23.908  16.544  9.577  2.841    .100    .319    .084  46.823 100.250

AVER:     .059  -.008  24.125  16.502  9.577  2.841    .100    .319    .084  46.823 100.423
SDEV:     .008   .007    .256    .036   .000   .000    .000    .000    .000    .000    .216
SERR:     .004   .003    .128    .018   .000   .000    .000    .000    .000    .000
%RSD:    13.91 -82.23    1.06     .22    .00    .00     .00     .00     .00     .00

PUBL:    n.a.    n.a.  23.957  16.359  9.577  2.841    .100    .319    .084  46.823 100.060
%VAR:     ---     ---     .70     .88    .00    .00     .00     .00     .00     .00
DIFF:     ---     ---    .168    .143   .000    .000   .000    .000    .000    .000
STDS:     251    1023      14     336    ---     ---     ---     ---    ---    ---

So well within 1% relative accuracy on both Si and Al. Now for the nepheline (just looking at Si because this is the primary standard for Al):

ELEM:      Sr      Rb      Si      Al      Na      K      Fe      O      Ca  SUM  
  1383    .009    .030  20.553  17.872  12.552  4.657    .155  44.418    .075 100.322
  1384   -.002    .045  19.924  17.774  12.552  4.657    .155  44.418    .075  99.598
  1385    .006    .029  20.594  17.954  12.552  4.657    .155  44.418    .075 100.440
  1386    .002    .025  20.422  17.857  12.552  4.657    .155  44.418    .075 100.163

AVER:     .004    .032  20.373  17.864  12.552  4.657    .155  44.418    .075 100.131
SDEV:     .005    .009    .308    .074    .000   .000    .000    .000    .000    .373
SERR:     .002    .004    .154    .037    .000   .000    .000    .000    .000
%RSD:   134.64   27.41    1.51    .41     .00     .00     .00     .00     .00

PUBL:     n.a.    n.a.  20.329  17.868  12.552  4.657    .155  44.418    .075 100.054
%VAR:      ---     ---     .22  (-.02)     .00    .00     .00     .00     .00
DIFF:      ---     ---    .044   (.00)    .000   .000    .000    .000    .000
STDS:      251    1023      14     336     ---     ---     ---     ---    ---

Again excellent accuracy extrapolating from SiO2. Now our orthoclase standard:

ELEM:      Sr      Rb      Si      Al      Fe      K      Na      Ba      O  SUM  
  1387    .005    .120  29.905  8.844  1.461  12.859    .675    .054  45.798  99.721
  1388   -.011    .121  29.736  8.860  1.461  12.859    .675    .054  45.798  99.553
  1389   -.001    .087  30.128  8.792  1.461  12.859    .675    .054  45.798  99.853
  1390   -.010    .117  30.202  8.773  1.461  12.859    .675    .054  45.798  99.929

AVER:    -.004    .111  29.993  8.817  1.461  12.859    .675    .054  45.798  99.764
SDEV:     .008    .016    .212   .041   .000    .000    .000    .000    .000    .165
SERR:     .004    .008    .106   .021   .000    .000    .000    .000    .000
%RSD:  -172.78   14.61     .71    .47    .00     .00     .00     .00     .00

PUBL:     n.a.    .027  30.286  8.849  1.461  12.859    .675    .054  45.798 100.009
%VAR:      ---  311.36    -.97   -.36    .00     .00     .00     .00     .00
DIFF:      ---    .084   -.293  -.032   .000    .000    .000    .000    .000
STDS:      251    1023      14   336     ---     ---     ---     ---     ---

Again within 1% relative accuracy for both.

In other prior work I've seen similar accuracy extrapolating from MgO to other Mg silicates, so I do believe these extrapolations are feasible, though we will see in the case of Al Ka since we already know from work by Fournelle that there are subtle Al peak position shifts in feldspars at least.

By the way, these measurements were performed at 50 nA because the purpose was to look at the trace elements, but the beam was defocused to 10 um to minimize TDI effects. Never the less, some intensity changes over time were observed as shown below, but only for the Si Ka emissions!

(https://smf.probesoftware.com/gallery/395_24_02_22_12_04_58.png)

The above being a normal exponential TDI fit. A hyper-exponential fit might be worth trying even though it appears to overfit, the intercepts are probably more accurate and that's what we utilized here:

(https://smf.probesoftware.com/gallery/395_24_02_22_12_07_02.png)

This resulted in a TDI correction of around 1.7% +/- 0.2 for Si Ka and 0.34% +/- 0.1 for Al Ka in the labradorite

Anyway, bottom line is that major element matrix correction extrapolations can be quite accurate even when extrapolating from a pure oxide to a silicate mineral, and the valence and coordination effects seem to be minimal.

I just wanted to address a question on the purity required for synthetic standards that we utilize as primary standards for major element analysis.  In other words, how pure do these synthetic mineral standards really need to be?

My answer would be that I think we should be initially focused on major element standards. The main reason being to guide analysts away from the seduction of so called "matrix matched" standards of questionable accuracy (and availability).  Instead what we need are high accuracy (and high availability) major element standards, e.g., MgO, Mg2SiO4, MgAl2O4, SiO2, Fe2SiO4, Fe3O4, etc., etc.

Trace element (doped) standards are really not necessary in my opinion. The only thing we need for trace element accuracy are pure metals or simple oxides for primary standards (and their accuracy is not all that important!). What's important for trace elements is the background modeling! And optionally also high purity blank (possibly matrix matched) materials for the application of a blank correction.  Doped trace standards are for dopes!  😁

Back to major elements, our preliminary MgO, Al2O3, MgAl2O4 FIGMAS data reported by Will shows that with accurate dead time calibrations we can obtain better than 1 to 2% accuracy extrapolating from simple compounds to significantly different compositions ( I obtained similar results myself with the test mount).  And also my own long term experience with other high concentration primary standards for other elements, and a recent test using SiO2 as a primary standard here:

https://smf.probesoftware.com/index.php?topic=1415.msg10574#msg10574

shows similar sub 1% accuracy.  The good news is that our modern matrix corrections are pretty damn good, the weak point being the dead time calibrations on our instruments.  And those can be easily fixed in a couple of hours work:

https://smf.probesoftware.com/index.php?topic=1160.0

So our concerns regarding trace elements in these synthetic materials I think should only be relative to the extent to which these traces affect the accuracy of the theoretical (major element) stoichiometry of these synthetic compositions.  So to me that means 99.99% purity is just fine. A 100 ppm variance on our major elements is not a significant concern.

Attached below is the latest draft of the action plan of global standards (login to see attachments).

If anyone has additional information (e.g., additional suppliers of high purity synthetic single crystals), just send me the information and I will add it to the document.

Thanks!

I have to say I am very much enjoying the book "Beyond Measure":

https://www.amazon.com/Beyond-Measure-History-Measurement-Constants/dp/1324035854

In the section on the effort to redefine the kilogram, they mention the concept of standards "For All Times, For All Peoples":

https://www.nist.gov/blogs/taking-measure/all-times-all-peoples-how-replacing-kilogram-empowers-industry

Although our standards (as far as I can imagine) will always be physical objects, we can definitely place them on a basis more akin to the "For All Times, For All Peoples" concept.

For example, instead of defining an olivine standard as a crystal that came from a specific outcrop (on a specific date and collected by a specific person), with all it's natural heterogeneity, inclusions and limited availability, we can instead define our olivine standard as a material that contains 2 atoms of Mg, 1 atom of Si and 4 atoms of O.

In other words single crystal Mg2SiO4, which is available commercially in essentially unlimited quantities, with high purity and can therefore be distributed globally and re-sourced and/or reproduced easily in the future.  Unlike every naturally sourced material we currently have in our collections!

Remember also that such a standard can not only be utilized as a highly accurate primary standard for Mg, but also as an accurate blank standard for any trace element, in order to test ones ability to measure zero in an olivine matrix:

https://smf.probesoftware.com/index.php?topic=454.msg11753#msg11753

Now it's true that synthetic high purity Fe2SiO4 is not available commercially that I know of, though I'm sure further efforts could be made to synthesize it (as it has been successfully synthesized at Oak Ridge National Laboratory by Lynn Boatner because I have a nice piece of it!), though I suspect we would also have excellent results using almost any other synthetic Fe oxides (e.g., Fe3O4) for the analysis of Fe in olivines.

Is anyone willing to search their closets and attics for a possible source for such previously grown materials?  I'm looking at you national lab people!

Quote
Treasures in your attic (or more likely your lab cabinets)!

The authors of this open letter believe that one possible source of such stoichiometric materials could come from past efforts by our colleagues in the crystal growth community to create large crystals of stoichiometric compounds. Such efforts might have resulted in archiving some of these materials, perhaps forgotten at the back of a lab cabinet, that could now be repurposed to serve as ideal standards for the microanalysis community. Ideally we are seeking quantities in the 500 to 1000 gram or more quantities, for example:

Mg2SiO4, YAG, RbTiOPO4, KTiPO4, MnO, Fe3O4, NiO, ZnO, LaAlO3, MnPSe3, LiTaO3, ZrSiO4 (zircon), ZrO2 (zirconia), HfSiO4 (hafnon), HfO2 (hafnia), ThSiO4 (tetragonal thorite), ThSiO4 (monoclinic huttonite), Fe2SiO4 (fayalite), Mn2SiO4 (tephroite), CaMgSi2O6 (diopside), Al2SiO5 (sillimanite), NaAlSiO4 (nepheline), KAlSi3O8 (sanidine), KAlSi2O6 (leucite), KAlSi3O8 (orthoclase), NaAlSi3O8 (albite), CaAl2Si2O8 (anorthite), Fe3Al2Si3O12 (almandine), PbSiO3 (alamosite), CaAl2O4 (krotite), CaAl4O7 (grossite), CaAl12O19 (hibonite), CaSiO3 (wollastonite), MgSiO3 (enstatite), FeSiO3 (ferrosilite), sulphides and sulfosalts, etc., etc.

Do you have access to such materials in your laboratory, or know of materials located elsewhere, that you would be willing to share with your colleagues worldwide in this important endeavor? If so, we would welcome your participation and ask that you contact the MAS FIGMAS on Standards with any information that can advance our "quest for fire"!

a plea from Dale Newbury

RESEARCH quantities of many materials were grown by national labs, after funding defined the possible or expected military or aerospace applications.  Research quantities were +/- 100 grams per batch.   Batch to batch variations from flux are common.  Single crystals would never be possible from fusion of a gel or other simple prep.

This means NOT ALL materials and NOWHERE NEAR the kilogram goal of the new collection.    It also means BATCH TO BATCH VARIATIONS  as opposed to the "unlimited" commercial prep of POWDERS.  A stated goal of the new collection was to avoid "flyspeck" mounts--that means that this becomes a series of custom syntheses of multiple batches.

The number of experienced crystal growers in both public posts and the pdf attachments runs about 1% of the responders.  We have all posted far higher costs and minimum equipment requirements for one reason--we actually know how difficult it is to grow a 1mm sized single crystal of a material that does not undergo a phase change during growth.

My own years of work have been summarized by a user as "secret sauce" https://smf.probesoftware.com/index.php?topic=1520.0  This is actually more polite than many offensive in-house emails that accused me of "just making work" while crystal production was being optimized. 

My final point is this: that perfect record keeping is also more important than anybody thinks.  I am the only person who is willing to admit that I kept a legal copy of some Astimex records.  Astimex Standards stopped answering calls and emails sometime in 2018.  HOW do future collections plan to prevent this dead airspace?

Quote from: crystalgrower on April 28, 2023, 09:03:29 AM
RESEARCH quantities of many materials were grown by national labs, after funding defined the possible or expected military or aerospace applications.  Research quantities were +/- 100 grams per batch.   

If we distributed mounts with 500 milligrams of material each, that would still be enough material for 200 microanalysis laboratories.  That's a good start for global distribution set!

How can we locate these "hoards" of single (or poly) crystal material?  We need to talk to these people and find out what they know. I have heard rumors that many such experiments in various national labs in the US, China and Russia produced large quantities of material, but the trick is locating these "buried treasures".

Especially materials which are evidently not currently produced commercially.  A few such materials would be of great interest to us in the microanalysis world are listed here:

QuoteZrSiO4 (zircon), ZrO2 (zirconia), HfO2 (halfnia), ThSiO4 (tetragonal thorite), ThSiO4 (monoclinic huttonite), Fe2SiO4 (fayalite), Mn2SiO4 (tephroite), CaMgSi2O6 (diopside), Al2SiO5 (sillimanite), NaAlSiO4 (nepheline), KalSi3O8 (sanidione), KAlSi2O6 (leucite), KAlSi3O8 (orthoclase), NaAlSi3O8 (albite), CaAl2Si2O8 (anorthite), Fe3Al2Si3O12 (almandine), PbSiO3 (alamosite), CaAl2O4 (krotite), CaAl4O7 (grossite), HfSiO4 (hafnon), CaAl12O19 (hibonite), CaSiO3 (wollastonite), MgSiO3 (enstatite), FeSiO3 (ferrosilite).

Please read Dale Newbury's message quoted here for more details:

https://smf.probesoftware.com/index.php?topic=1415.msg11754#msg11754

A mount with 500mg is 10X more than what had been very widely sold in the past.

Labs do not use large-item mounts in routine work because they take up too much space.  Many labs have filled corners and interstices between 25mm holes with 10mm mounts.
Charles Taylor started cutting materials into 2 x 2 x 2mm cubes which works out to 0.008cc or  20-50mg of material. I guess there would be some waste for cutting.  You can mount at least 40 of these into a 25mm circle.  Taylor used drilled steel cups (expensive)  and Rucklidge used brass rings.   Both mount styles have a working life of 40+ years depending on the care.

Public Appeals

The pandemic closed down the personal contacts at major meetings of MSA (mineralogists)  and  ACS and AGU. The old stashes, if they still exist, will be found by direct contacts. 
Access to foreign collections means asking for help from people who can read Russian or Chinese and who have time to trawl through google.   

A letter in Elements Magazine would reach some of the  Asian member groups. 

A special Elements issue on the comprehensive subject of EPMA history and calibration might be useful but it will take 2 years to get off the ground.   This is where you write an article asking for global participation in the k-values project. 

The Taylor and Astimex stashes were handed over by Rucklidge to Mike Gorton who is still listed at the University of Toronto.  The Taylor stash had plenty of YAG, SIO2, Al2O3, and synthetic pyroxenes and spinels.   Also exceptional minerals like Foord spessartine and Rucklidge Batbjerg Cr-diopside.  The simplest compounds were stockpiled for working standard mounts because they represented the highest concentration possible. 

There are also cases of "too little too late". 

There was a commercial outfit with large volume hydrothermal systems for producing synthetic minerals.  They got SBIR grants in 2006 and 2008 and were out of business before 2015.  They would have been the ideal outfit to replace Pb-contaminated monazites using the high-efficiency process published in 2003.

Dorian Smith who had some supply of synthetic spinels (CoAl2O4 etc)  died in 2013 after which his company Micronex shut down. 

And of course REE.

You need REE phosphates  for the SEM-SDD-EDS that is the new fast sensitive screening  analysis.  Neither the Drake or Edinburgh REE glasses are optimal.  Never mind that the process for the Edinburgh glass was published--useful details are missing.  But the Si-Al matrix is a waste of time for REE.

SO—Nobody has bought my orthorhombic  RP5O14 for a decade.  I am in a position to start  production of  mixed phosphate crystals to replace Si-Al REE glasses. Hydrothermal  monazite is a really good matrix for mixed cations.  But there is no reason to think that anybody will accept it from me.

Quote from: crystalgrower on May 29, 2023, 09:06:46 AM
A mount with 500mg is 10X more than what had been very widely sold in the past.

Yes, exactly my point. Even if we could produce only 100 grams of each material, we'd still have plenty of material to distribute to every microanalysis lab in the world.  It's also not a bad idea to have a reserve of material set aside for future mount production.

Quote from: crystalgrower on May 29, 2023, 09:06:46 AM
The pandemic closed down the personal contacts at major meetings of MSA (mineralogists)  and  ACS and AGU. The old stashes, if they still exist, will be found by direct contacts. 

Access to foreign collections means asking for help from people who can read Russian or Chinese and who have time to trawl through google.   

A letter in Elements Magazine would reach some of the  Asian member groups. 

I'm giving a talk to a Chinese EPMA group this week and I will make that appeal directly to them.  A letter in Elements magazine is a good idea.

FIGMAS* Election results:

Hi everyone, just a heads-up that the FIGMAS elections have been held, and the results are in. Aurelien Moy will be FIGMAS Leader in 2027-2028, while Andrew Mott will continue on as Secretary/Treasurer in 2025-2026, with Abigail Lindstrom as Leader.

Thanks to everyone who took part! If you are not a FIGMAS member but would like to become one, please consider signing up at the FIG Store: https://portal.microscopy.org/Portal/Member_Portal/FIG_Store/Portal/Store_Layouts/FIG_Store.aspx.

Thanks!
Emma
FIGMAS Leader 2023-2024

*The Focused Interest Group on MicroAnalytical Standards (FIGMAS) aims to evaluate and catalogue microanalytical standards and reference materials (S-RM) and to facilitate accessibility of these materials to the microanalysis community (EPMA, SEM, LA-ICP-MS...). It is the first group to have been created and approved with the joint support of both MSA and the Microanalysis Society (MAS).

To learn more about FIGMAS, please check out our webpages at https://microscopy.org/mas-fig and https://figmas.org/

I am a member of EMAS (Europe based society) and tried to sign up to FIGMAS. I got back the email that I should be a member of MAS or MSA to be able to sign up. I find it kind redundant to do that as I am already a member of European Microbeam Analysis Society, but If I need to join one of MAS or MSA, which would you recommend?

MAS is the microanalysis society, MSA is microscopy, so I've gone for MAS.

It has been a long-term frustration to FIGMAS that the group is only open to MAS/MSA members.  The organization would very much like to permit EMAS and AMAS (and other microanalysis society) members to join without having to join MSA or MAS.  However, MSA is a bit of a stick in the mud and FIGMAS hasn't been able to figure out a way around their rules without some serious penalties.