I think it would be very helpful for promoting standards-based EDS analysis if the community were to provide a recommended set of basic EDS standards for each accessible element in the periodic table. These materials could be build into standard blocks which commercial vendors or laboratories could build in volume (relatively speaking). Such blocks would lower the barrier to standards-based analyses.
The basic EDS standards would be either pure elements or simple stoichiometric compounds. This way anyone could reproduce them and know that there composition was what it was claimed to be.
Ideally, the samples would be robust and not susceptible to environmental degradation or degradation under the beam. Ideally, the samples will be available in "bulk" form. (At least 100 µm on edge) Ideally, they would not require any maintenance that requires expensive equipment. They could be polished by hand following provided instructions and then recoated with carbon as necessary.
The choice of standards need not be optimal for all analyses. Sometimes perfect is the enemy of good enough. But because they were shared and available to all, they could encourage people who would like better analyses but find the task too daunting to perform standards-based analyses.
Furthermore, these basic standards could be the foundation for a set of "digital standards" that allow users to trade k-ratios rather than materials to optimize their measurements using "matrix matched standards." This would bring the best of both worlds - easier standards-based analyses and more accurate analyses.
One requirement for these basic EDS standards that is distinct from WDS standards is that the standards should avoid peak interferences. Pure elements are easy but many stoichiometric compounds have interferences that are not an issue for WDS but make unsuitable for EDS. It isn't that EDS can't handle interferences; it is simply that ensuring the basic EDS standards don't have interferences allows them to double as peak shape references. This greatly simplifies quantification for novices.
I have some ideas based on my experience what I'd suggest for most elements. But I also have many questions that the WDS community could help with. Frequently, I wonder whether it would be better to choose a robust material like "FeS2" over "Pure Fe", "Al2O3" over "Al" because they are likely to age better. Some elements are really hard. Some elements seem to lack obvious robust alternatives. Is there something better than "NaCl" or "KCl" for chlorine? "RbI" for rubidium?
My "starter list"
H – N/A
He – N/A
Li – N/A
Be – Be
B – BN
C – C
N – BN
F – CaF2
Ne – N/A
Na – NaAlSi3O8
Mg – MgO
Al – Al2O3
Si – SiO2
P – GaP
S – FeS2
Cl – NaCl, KCl
Ar – N/A
K – KBr
Ca – CaF2
Sc - Sc
Ti - Ti
V - V
Cr - Cr
Mn -Mn
Fe – Fe
Co - Co
Ni - Ni
Cu - Cu
Zn - Zn
Ga - GaP
Ge - Ge
As - ?
Se - Se
Br - KBr
Kr – N/A
Rb - RbI
Sr – SrF2
Y - Y
Zr - Zr
Nb - Nb
Mo - Mo
Tc – N/A
Ru - Ru
Rh - Rh
Pd - Pd
Ag - Ag
Cd - Cd
In - In
Sn - Sn
Sb - Sb
Te - Te
I – RbI
Xe – N/A
Cs – CsCl
Ba – Sanbornite (BaSiO5) and
La – LaB6, LaP5O14
Ce – CeAl2
Pr – PrP5O14
Nd – NdP5O14
Pm – PmP5O14
Sm – SmP5O14
Eu – EuP5O14
Gd – GdP5O14
Tb – TbP5O14
Dy – Dy, DyF3
Ho – HoF3
Er – Er, ErF3
Tm – TmF3
Yb – YbF3
Lu – Lu, LuF3
Hf - Hf
Ta - Ta
W - W
Re - Re
Os - Os
Ir - Ir
Pt - Pt
Au - Au
Hg - HgTe
Tl - Tl
Pb - PbO
Bi - Bi
Po – N/A
At - N/A
Rn - N/A
Fr – N/A
Ra – RaCO3
Ac - ?
Th – ThO2
Pa – N/A
U – UO2
Np - N/A
Pu - N/A
What do you think? Do you have some favorite standards that I've overlooked? Have I made some poor choices?
I think this is a very worthy cause, though my impression is that the instrument vendor supplied mounts already typically contain pure metals and simple oxides (purity?). At least my Cameca instrument came with such a mount though I almost never used it. As for SEM/EDS vendors do any manufacturers provide similar standard mounts?
I suspect that the much bigger problem is getting SEM users to use any standards at all! To wit:
https://smf.probesoftware.com/index.php?topic=1761.0
Does anyone have any polling data on what percentage of analyses are performed on SEMs using standards versus standardless? Would the EDS vendors have any inkling of these percentages?
In my past discussions with EDS vendors, they have told me that almost none of their customers use standards, but what do we actually know?
I view this as an attempt to pull a fraction (albeit a small fraction) over to standards-based analysis. Make it as easy as possible with as few decisions as possible and maybe a few more people will give it a try.
Because EDS detectors are so stable, you really only need to collect new standards occasionally. If you are willing to investment a day collecting standards, standards-based analysis can be as simple as standardless.
Sure some vendors provide a handful of pure metals and oxides but are they selected to be optimal for EDS? Do they cover enough of the periodic table? How many people have attempted to perform standards-based EDS only to find they missed a suitable standard for one element? Let's solve this problem by covering the entire accessible periodic table with EDS suitable standards.
Combine "virtual standards" with 2 or 3 comprehensive standard blocks and we could have a future in which EDS provides the accuracy of "matrix matched standards" with "close to the convenience" of standardless.
Part of the reason no-one uses standards because no-one has made it easy to use standards. That is what I'm trying to do with this project.
As I said, this is a very worthy cause.
And yes, I agree, if you want people to do something correctly, you need to make it easy to do.
Right now, my experience with Bruker/Thermo EDS software and standards is that it's much easier to do standardless, so anything to make it easier would be great.
Does it make any sense for DTSA2 to start interfacing with various EDS vendor hardware? That is why I went to the effort in Probe for EPMA to interface to both JEOL and Cameca, then one can control the standardization method and make it easier.
In PFE, the standardization data is acquired exactly similar to the unknown data so there is really nothing more to learn. And users tend to want to focus on acquiring unknown data more than standard data.
But as you said, with EDS it should be even easier as the frequency of re-calibration should be less.
Any overarching suggestions/thoughts on selecting durable standards? When would you consider using a binary when the pure element is available?
Owen Neill suggested InAs for As. The In M-lines are below the As L and the In L-lines are below the As K. It is a semiconductor and could serve for both In and As.
For minor/trace element analyses, I would always use a pure metal or pure oxide if available.
As you well know, for minor/trace elements the background characterization is the most important parameter and a high concentration (that is count rate per concentration) in the primary standard gives the best sensitivity. That statement pretty much covers everything except the alkali metals, liquids/gases.
For major elements the standard accuracy (and matrix correction accuracy) are most important, and the chemical effects might also be worth considering (at least for low energy emission lines), so here is my list divided two ways into elemental/alloy and oxides/silicates:
Elemental Oxides/silicates
H - N/A H - N/A
He - N/A He - N/A
Li - N/A Li - N/A
Be - Be Be - BeAl2O4 (synthetic)
B - BN B - LaB6 or BN or HfB2
C - C C - CaCO3 (water clear calcite)
N - BN N - Si3N4 or AlN or GaN
O - ? O - MgO or SiO2
F - CaF2 F - Na5Al3F14 (synthetic chiolite)
Ne - N/A Ne - N/A
Na - Na5Al3F14 (chiolite) Na - NaAlSi3O8 (albite)
Mg - MgO Mg - Mg2SiO4 (synthetic forsterite)
Al - Al Al - Al2O3
Si - Si Si - SiO2 or Mg2SiO4 (synthetic forsterite)
P - GaP or InP P - GaP or NBS K-496 glass or ScPO4
S - FeS2 or CdS (synthetic) S - CaSO4 (anhydrite)
Cl - RbCl Cl - RbCl
Ar - N/A Ar - N/A
K - KBr K - KTaO3 or KAlSi3O8 (orthoclase)
Ca - CaF2 Ca - CaSiO3 (synthetic wollastonite)
Sc - Sc Sc - ScPO4
Ti - Ti Ti - TiO2
V - V V - V2O3
Cr - Cr Cr - Cr2O3
Mn - Mn Mn - MnO
Fe - Fe Fe - Fe2O3 or Fe3O4
Co - Co Co - CoO
Ni - Ni Ni - NiO or Ni2O4
Cu - Cu or Cu2S (chalcocite) Cu - Cu2O (synthetic)
Zn - Zn or ZnSe Zn - ZnO
Ga - GaP Ga - Gd3Ga5O12 (GGG)
Ge - Ge Ge - Ge
As - GaAs or InAs As - GaAs or InAs
Se - Se or ZnSe Se - Se or ZnSe
Br - KBr or CsBr Br - KBr or CsBr
Kr - N/A Kr - N/A
Rb - RbTiOPO4 Rb - RbTiOPO4
Sr - SrF2 Sr - SrTiO3
Y - YAG or YIG Y - YAG or YIG or YPO4
Zr - Zr Zr - ZrSiO4 (synthetic zircon)
Nb - Nb Nb - LiNbO4 LiNbO3
Mo - Mo Mo - PbMO4
Tc - N/A Tc - N/A
Ru - Ru Ru - Ru
Rh - Rh Rh - Rh
Pd - Pd Pd - Pd
Ag - Ag or Ag2S Ag - Ag
Cd - Cd or CdS Cd - Cd or CdS
In - In or InP In - In or InP
Sn - Sn Sn - Sn or SnO2
Sb - Sb or GaSb (synthetic) Sb - Sb or GaSb (synthetic)
Te - Te or NiTe (synthetic) Te - Te or NiTe (synthetic)
I - RbI or CsI I - RbI or Cu(IO3)(OH) (salesite)
Xe - N/A Xe - N/A
Cs - CsCl or CsBr Cs - CsCl or CsBr
Ba - BaF2 Ba - BaSiO5 (sanbornite) or BaSO3 (barite)
La - LaB6 or LaF3 La - LaPO4 (synthetic)
Ce - CeAl2 or CeF3 Ce - PrPO4 (synthetic)
Pr - PrP5O14 Pr - PrPO4 (synthetic)
Nd - NdP5O14 Nd - NdPO4 (synthetic)
Pm - PmP5O14 Pm - PmPO4 (synthetic)
Sm - SmP5O14 Sm - SmPO4 (synthetic)
Eu - EuP5O14 Eu - EuPO4 (synthetic)
Gd - GdP5O14 Gd - GdPO4 (synthetic)
Tb - TbP5O14 Tb - TbPO4 (synthetic)
Dy - Dy, DyF3 Dy - DyPO4 (synthetic)
Ho - HoF3 Ho - HoPO4 (synthetic)
Er - Er, ErF3 Er - ErPO4 (synthetic)
Tm - TmF3 Tm - TmPO4 (synthetic)
Yb - YbF3 Yb - YbPO4 (synthetic)
Lu - Lu, LuF3 Lu - LuPO4 (synthetic)
Hf - Hf or HfC Hf - HfSiO4 (synthetic)
Ta - Ta Ta - KTaO3 (synthetic) or CrTa2O6 (synthetic)
W - W W - PbWO4 (synthetic)
Re - Re Re - Re
Os - Os Os - Os
Ir - Ir Ir - Ir
Pt - Pt Pt - Pt
Au - Au Au - Au
Hg - HgTe Hg - HgTe
Tl - Tl Tl - Tl
Pb - PbS (synthetic galena) Pb - PbSiO3 (alamosite) or PbMoO4 (wulfenite)
Bi - Bi Bi - Bi2O3
Po - N/A Po - N/A
At - N/A At - N/A
Rn - N/A Rn - N/A
Fr - N/A Fr - N/A
Ra - RaCO3 Ra - RaCO3
Ac - ? Ac - ?
Th - ThC Th - ThO2 or ThSiO4 (synthetic)
Pa - N/A Pa - N/A
U - UO2 U - UO2 or USiO4 (synthetic)
Np - N/A Np - N/A
Pu - N/A Pu - N/A
Also, oxides/silicates tend to oxidize less than pure elements or alloys, so there is some additional advantage in using oxides/silicates in standard mounts.
BTW, I just noticed that one of my standard names in the UofO standard database has a typo. Standard 259 should be BeAl2O4, not Be4Al2O4! However, the composition was correct, so just edit the standard name and all is good.
Also, I've always referred to the Smithsonian (Boatner) REE phosphates as PO4, but I see you have the REE phosphates as P5O14. Are those from another source?
Thanks, this is really helpful. I'm coming around to the idea of using oxides like Al2O3 and SiO2 rather than pure elements although you do have to coat and even then the Duane-Hunt is often a little (100 eV-ish) surpressed. Does anyone else have some suggestions?
The phosphates are "SPI Rare Earth Phosphates" . I recall that they are of Chineses origin via Astimex and are XP5O14. Seee https://astimex.com/com/catalog/reep.html
I can offer a shortlist of forms that should NOT be used for standards. Based on years of purchasing for Astimex (check their website for details which still appears to be online) which have been in use for EDS since 1969. FYI SPI Supplies does not maintain their online catalog any longer. I still have the EDS spectra archived...my apologies for many updates.
Use of binary compounds such as GaAs and InP and Sb2S3 take care of many nonmetallic elements on EDS. Astimex catalog only offered the beam- stable ones. LiF , BN, also useful and no overlaps.
Avoid graphite electrodes as a source of C (too porous)
Try to find an older source of Zr metal rod as the currently available wire has a hole down the middle. This is partly due to Zr being classified as "reactor material". Check both Zr and Hf for purity from the other element (price will be higher) because these have perfect overlap for EDS. And ZrO2 NOT good because it will have too much of both Y and Hf with perfect overlap on EDS.
We had success with Os, Ru, and other refractory metals from Metallium that they melted by electrical current in vacuum. They tracked the original certificates of analysis faithfully and did custom cuts. We never found any other acceptable form of Os metal
Optical grade Tl(Br,I) from a reliable source is the only really stable material for all three elements. Sold as KRS-5 for infrared optics, it is 6N and the eutectic composition. Both TlBr and TlI are difficult to polish and rarely available as crystals.
Th wire is good and available but must be kept dessicated.
I posted instructions on this forum for easy synthesis of K2SiF6, Rb2SnF6 and Cs2SiF6 which are far more homogeneous than any minerals. Avoid pollucite unless you can find a clean museum specimen.
Black "cassiterite" is closer to FeSn2O3 than SnO2. A museum specimen of white SnO2 would not be better than Sn metal.
For Cu use OFHC wire NOT any oxide.
Do not use Mg foil. FAR too fragile.
Be careful that Be metal has no Al or flux present.
RaSO4 more beam stable than RaCO3 and not hard to grow crystals.
UO2 notorious for being nonstoichiometric. DU if you can find it would be the only real choice.
Use Y and V unless you have access to hydrothermally recrystallized YVO4. ALL Y-P compounds have perfect overlap.
When considering sulfides, ZnS is preferable to FeS2 because Zn has no redox complications. ZnS is another optical material available 6N pure, it's translucent yellow.
Boatner RPO4 only good for Tb-Lu and Y. Contact me about La-Gd as PO4 offline.
Please contact me offline for rare earth pentaphosphates. I was the last supplier to Astimex.
Other options for REE are metals for Sm and higher and fluorides for La-Eu.
Thanks for all the suggestions crystalgrower. I'm going to have to go through your note line-by-line.
Quote from: crystalgrower on August 09, 2025, 08:18:42 AMWe had success with Os, Ru, and other refractory metals from Metallium that they melted by electrical current in vacuum. They tracked the original certificates of analysis faithfully and did custom cuts. We never found any other acceptable form of Os metal
We obtained some 99.997% Ru powder from Aesar and vacuum arc melted it ourselves.
Interestingly oxford instruments seems to sell standard blocks, not cheap at £3-4K.
https://nano.oxinst.com/assets/uploads/products/nanoanalysis/documents/Brochures/Technical%20Datasheets/AZtecWave%20AZtec%20Standards.pdf (https://nano.oxinst.com/assets/uploads/products/nanoanalysis/documents/Brochures/Technical%20Datasheets/AZtecWave%20AZtec%20Standards.pdf)
Not sure who makes them. Obviously more generally with EPMA there seems to be a lack of commercial standard blocks of well characterised standards.
I would like to know if NIST is planning to front the funds to either purchase wire anjd solids to be sold as small cuts, or is NIST considering preparing mounts.
FYI Astimex never patented or registered or copyrighted any mount layouts so they can be produced by anybody. The holes were 2mm drill bit drilled 2mm deep using a radial stepping microlathe setup.
It is very time efficient to make 10 mounts at a time. For Astimex/SPI the wire was cut and dropped into each well according to the printed layout, and then Buehler EpoHeat was added to bond each round. Polishing can be expedited by clearing off nubs of wire with a diamond wafer saw (which also means much less polishing time and media). The cost of materials and all prep for 48 wells would be about $2000 CDN at current "expert" wages. Resellers always add their own markup, so NIIST can offer the best price by only selling direct.
NIST would never attempt to produce mounts like this for the commercial market. My intent is to determine a "reasonably good" set of "EDS standards" that any vendor (or individual) could produce and sell. They would be carefully selected to make EDS standards-based quant relatively easy as well as facilitating the creation and sharing of "virtual standards."
I've summarized the conversation so far in this table.
The optimal column is my current thinking about the best choice to use as "transfer standards" for EDS analysis - robust, available, no peak interferences, etc.
(https://smf.probesoftware.com/gallery/399_20_08_25_9_54_37.png)
Here is the best for EDS list that was placed on the commercial market in 2010.
Li-LiF
Be
B-BN
C-pyrolytic plate
N-BN
O-MgO
F-LiF
Na-Na3AlF6
Mg-MgO
Al, Si element
P from GaP or InP
S from ZnS
Cl from K2PtCl6
K from K2PtCl6
Ca-CaF2
Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn metal
Ga-GaAs or GaP
Se element
As from GaAs
Br from Tl (Br,I)
Rb from Rb2SnF6
Sr from SrF2
Y,Zr, Nb, Mo, Ru, Rh, Pg, Ag, Cd from metal
InP as In difficult to polish
Sn, Sb, Te as element
I from Tl(Br,I)
Cs-Cs2SiF6
Ba-BaF2
La, Ce, Pr, Nd, Sm, Eu as RF3
Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au as metal
Hg as Hg2Te
Tl from Tl(Br,i)
Bi metal
The constraints which are required in addition to no overlap are INSOLUBLE, SYNTHETIC, and MELTING OVER 100C.
These materials were all checked for overlap in both EDS and WDS. Any trivial EDS overlap in minor peaks was accepted if no other substance could be mounted and remain stable. AND a ;license required to purchase RaSO4 and DU. You might get lucky with Th.
FYI peak shape is a function of detector. Overload any detector and the peak energy shifts to higher channels AND spreads out.
Quote from: Probeman on August 05, 2025, 09:19:54 AMNb - LiNbO4
Out of curiosity, why the preference for LiNbO4 over a simple oxide like Nb2O5? Ted Pella are listing Nb2O5 with a 3N5 purity rating. Is there a stability issue or something?
LiNbO4 seems an odd choice for a reference material where most people can't analyse one of the major constituents (Li).
Quote from: JonF on September 30, 2025, 06:47:11 AMQuote from: Probeman on August 05, 2025, 09:19:54 AMNb - LiNbO4
Out of curiosity, why the preference for LiNbO4 over a simple oxide like Nb2O5? Ted Pella are listing Nb2O5 with a 3N5 purity rating. Is there a stability issue or something?
LiNbO4 seems an odd choice for a reference material where most people can't analyse one of the major constituents (Li).
Interesting. I did not know this material is available. Indeed, Nb2O5 would be a great primary standard for Nb.
The fact that there are two high purity synthetic materials available, both containing Nb, is also a good thing for our consensus k-ratio project:
https://smf.probesoftware.com/index.php?topic=1442.0
That Li cannot normally be analyzed is no problem for its use as a standard, since all elements are declared in standard compositional databases.
Another point. When looking at the claimed purity of synthetic materials, be aware that sometimes they will claim something like "99.9% pure (metals basis)":
https://smf.probesoftware.com/index.php?topic=1504.msg11584#msg11584
LiNbO4? Personally I don't know this kind of material. There is indeed LiNbO3, Also there is LiTaO3. Both of these are synthesized in industrial quantities in very pure form as they are one of materials used in many optical devices. It is much easier to source pure synthetically grown crystals of these, than Nb2O5 which purity can be questionable (the purity of bulk quantities of Nb2O5 is not so industrially important compared to LiNbO3).
Right. LiNbO3.
Slightly off tangent, but when a standard material as the above LiNbO3 is listed as "high purity", is it simply the absence of significant concentrations of contaminants, or is it inferring that a material is (also?) stoichiometric?
Doing a (very) quick literature search suggests LiNbO3, Li3NbO4 and LiNb3O8 may all be made simultaneously, and all would pass a test for contaminants, but the resulting material would obviously not make a great standard material.
Quote from: sem-geologist on October 01, 2025, 01:41:50 AMLiNbO4? Personally I don't know this kind of material. There is indeed LiNbO3, Also there is LiTaO3. Both of these are synthesized in industrial quantities in very pure form as they are one of materials used in many optical devices. It is much easier to source pure synthetically grown crystals of these, than Nb2O5 which purity can be questionable (the purity of bulk quantities of Nb2O5 is not so industrially important compared to LiNbO3).
Yes.
I edited this post to reflect that:
https://smf.probesoftware.com/index.php?topic=1771.msg13570#msg13570
Quote from: JonF on October 01, 2025, 07:39:59 AMDoing a (very) quick literature search suggests LiNbO3, Li3NbO4 and LiNb3O8 may all be made simultaneously, and all would pass a test for contaminants, but the resulting material would obviously not make a great standard material.
Could you share that quick literature search?
I mean LiNbO3 grown using Czochralski process, that is a single uniform crystal with no boundaries or defects within. Can we go any further to define more "homogeneous" and more "pure" – purity of these are know to have contaminants at level below ppb's. Not some LiNbO3, LiNbO4, LiNb3O8 grown in some "kitchen sink" simultaneously from some Li,Nb rich "soup".
Quote from: sem-geologist on October 02, 2025, 12:58:59 AMQuote from: JonF on October 01, 2025, 07:39:59 AMDoing a (very) quick literature search suggests LiNbO3, Li3NbO4 and LiNb3O8 may all be made simultaneously, and all would pass a test for contaminants, but the resulting material would obviously not make a great standard material.
Could you share that quick literature search?
I mean LiNbO3 grown using Czochralski process, that is a single uniform crystal with no boundaries or defects within. Can we go any further to define more "homogeneous" and more "pure" – purity of these are know to have contaminants at level below ppb's. Not some LiNbO3, LiNbO4, LiNb3O8 grown in some "kitchen sink" simultaneously from some Li,Nb rich "soup".
Indeed Your pointing out made me worried. Seems that LiNbO3 can have defects of Li deficiency (vacancies) even then grown with Czochralski's process. My own LiNbO3 is a small cubic crystal and that makes me to suspect it rather was not grown using Czochralski process, but "kitchen sink" with Li,Nb rich "soup". While WDS scan at high current (1000nA) showed no detectible contaminants, about the Li:Nb:O ratio now I am on doubt.
Quote from: sem-geologist on October 02, 2025, 01:39:35 AMIndeed Your pointing out made me worried. Seems that LiNbO3 can have defects of Li deficiency (vacancies) even then grown with Czochralski's process. My own LiNbO3 is a small cubic crystal and that makes me to suspect it rather was not grown using Czochralski process, but "kitchen sink" with Li,Nb rich "soup". While WDS scan at high current (1000nA) showed no detectible contaminants, about the Li:Nb:O ratio now I am on doubt.
Sorry, I wasn't intending to worry anyone!
This was the stand-out paper that got me thinking:
Identification of LiNbO3, LiNb3O8 and Li3NbO4 phases in thin films synthesized with different deposition techniques by means of XRD and Raman spectroscopy, Bartasyte
et al, 2013,
DOI 10.1088/0953-8984/25/20/205901
Seems the different phases can be distinguished quite easily by Raman.
The paper was dealing with Li-Nb thin films deposited by various means - I've no idea how applicable it is to EPMA standards. I was just trying to see whether variations in Li:Nb stoichiometry could occur.
Going back to the topic, my point was simply that I'm not sure how much we can trust a standard when we can't verify it against our
other standards.
For example, potassium niobate (KNbO3)*, we would be able to measure the K and the Nb (and the O if you wanted!) and compare them against our other K and Nb (and O) standards. With lithium niobate, we're putting a lot of faith in the standard manufacturer to get what we asked for, although we could measure Nb and O.
*I've no idea whether KNbO3 would make a good standard, mostly likely not. It also looks to be toxic.
The major distinction is how these crystals are grown. Thin films for sure are not grown with Czochralski's process, thus it practically is not comparable. I think one of thing I could do with my own LiNbO3 standard is to try looking at it with EBSD, if it is monocrystal - there is higher chance it is a small regular shard from the larger crystal grown with Czochralski's process. Albeit these regular shapes are rather characteristic for small synthetic hydrothermal growth. Yes, for sure due to unmeasurable Li, we are at mercy of manufacturer and distributor, we have no easy way to verify its stochiometry.
Quote from: sem-geologist on October 02, 2025, 05:29:37 AMThe major distinction is how these crystals are grown. Thin films for sure are not grown with Czochralski's process, thus it practically is not comparable. I think one of thing I could do with my own LiNbO3 standard is to try looking at it with EBSD, if it is monocrystal - there is higher chance it is a small regular shard from the larger crystal grown with Czochralski's process. Albeit these regular shapes are rather characteristic for small synthetic hydrothermal growth. Yes, for sure due to unmeasurable Li, we are at mercy of manufacturer and distributor, we have no easy way to verify its stochiometry.
We had a similar problem with the RbTiOPO4 that Marc Schirer grew for me back in the day at UC Berkeley (now at The CalChemist). That is, how to know its stoichiometry given that we needed it as a Rb standard precisely because we didn't have any other Rb standard!
But we did measure the Ti using TiO2 and P using a YPO4 that we got from the Oak Ridge/Smithsonian, and of course checked it for impurities and homogeneity:
https://smf.probesoftware.com/index.php?topic=701.0
This summer at M&M I raised the issue of determining stoichiometric accuracy with a few of our colleagues and Ian Anderson mentioned that if one assumed that the stoichiometry was related to the degree of lattice defects, one might measure defects using a technique such as positron annihilation spectroscopy:
https://en.wikipedia.org/wiki/Positron_annihilation_spectroscopy
Not exactly a bench top characterization method, but maybe someone here has access to such a technique? I note that Washington University has such a device:
https://materialsresearch.wsu.edu/positronannihilationspectrometer/