Standards for EPMA-Cesium

[crystalgrower]

Cesium    A literature review of synthetic cesium silicate phases turns up  two materials CsAlSiO4 and CsAlSi2O6 that have been investigated for nuclear waste applications.

Recent info for CsAlSiO4 hydrothermal synthesis C. Diego Gatta et al, American Mineralogist (2008) Volume 93 pp 988-995.  Previous work by S.A Gallagher et al, Materials Research Bulletin (1977) volume 12 pp 1183-1190.

CsAlSi2O6 Classic “full gel” synthesis at 1100°C from CsNO3-Al(NO3)3-TEOS investigated by S.A Gallagher et al in Journal of Inorganic and Nuclear Chemistry (1981) vol 43 pp 1773-1777
Extremely valuable recent comments about  gel preparation have been posted online by the Edinburgh group for their prep of REE glasses.
There are also post-Fukushima  references to hydrothermal synthesis of pollucite which I have not read.

Stability of synthetic Cs-Al-Si phases studied by P. Taylor et al, Canadian Journal of Chemistry. (1989) volume 67 pp 76-81,  with a generous list of other syntheses.

Natural pollucite: I bought some of the gem quality Pakistan material, cracked it up in a steel mortar, and washed it through sieve stack of 10mesh-20mesh-pan with water. 
The 10-20 mesh fraction must be hand picked from immersion in isopropanol to eliminate  inclusions.  These are not visible at first glance.  I used a shallow white plastic dish (Mason jar lid) at 16X with fluorescent ring light.  I had to take each grain and rotate it by 180° in the solvent to see any flash from a second phase. 

NB Bernic Lake material was not formed at the same high temperature.  Some veins are good CsAlSi2O6, some have multiple Cs-Li phases, and some have large veins of SiO2. 

My observation about mineral pollucite is that material with measurable water present  in the structure might be considered a separate mineral, maybe called cesian analcime.  Bear in mind the parallel between garnet (anhydrous) and prehnite (hydrated).  Water is not required to balance the ion charge in Na-Cs solid solutions.  My gel experiments lead me to conclude that water is bound in the Na-Si-O precursor, and that it would be completely eliminated before the solid reaches 900°C.

Phosphates  Please see the excellent review of compounds by  A Orlova et al, Radiochemistry (2005) vol 47 pp 14-30 in English (Radiokhimiya same volume in Russian). No need for any hit-or-miss R&D effort. 

[Probeman]

Cesium    A literature review of synthetic cesium silicate phases turns up  two materials CsAlSiO4 and CsAlSi2O6 that have been investigated for nuclear waste applications.

Stability of synthetic Cs-Al-Si phases studied by P. Taylor et al, Canadian Journal of Chemistry. (1989) volume 67 pp 76-81,  with a generous list of other syntheses.

This is extremely interesting information.    Thank-you for posting it.

Can the CsAlSiO4 and CsAlSi2O6 materials be grown as stoichiometric (mm sized) single crystals?  Can they be grown in large enough quantities suitable for global distribution (~100 grams)?   Is this an expensive synthesis?   

[Probeman]

While we're on the topic of silicates, I note a poll we took some time ago identified end member fayalite, Fe2SiO4 (and topaz, Al2SiO4F2), as very sought after standard materials (synthetic fosterite, Mg2SiO4 is pretty readily available commercially).   

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

How would Fe2SiO4 be synthesized?    I once had a small single crystal from Lynn Boatner at Oak Ridge that was perfectly stoichiometric (and had no blebs of Fe metal, unlike the material from Tokyo Institute of Physics).  I wrote him a couple of years ago asking about his synthesis recipe but he never responded...

Is end member topaz easily synthesized (or available commercially)?    You probably have contacts in the industry.  Are there commercial growers out there that would be able to provide "cut-offs" or other scrap material for use as microanalysis standards for either of these materials?

[crystalgrower]

The two Cs-Al-Si phases have been grown as stoichiometric single crystals by hydrothermal process.  Probe sized product was one criterion I used to select the citations in all posts.  You would have to get a price quote for hydrothermal syntheses from somebody with the apparatus.  You are looking for a larger reaction chamber for production scale. 

I put my topaz info into the halides post.

There was a published HT synthesis of Ni2SiO4 and Co2SiO4 by Jun Ito in American Mineralogist  a few decades ago.  Same exact process could be used for Fe2SiO4.  I would actually start from a gel rather than pure oxides, because the synthesis from oxides reported a very slow reaction rate.  Premixing solutions of the soluble sulfate and sodium metasilicate to form a hydrated precipitate should be a whole lot easier to crystallize. 

In 2012  somebody showed me some Co spinel.  Clear deep blue stuff in mm grains, I have no idea what the composition was.  CoAl2O4 would be a first guess.

[crystalgrower]

Relevant to your requests:

Robie et al, American Mineralogist (1984) vol 69 p 1096 Ni and Co olivines

Fisher et al American Mienralogist (1969) vol 54 p 741, Mg and Fe olivines

Ito, American Mineralogist (1968) vol 53 p 1296 Scandium analogues of several compounds starting with NaScSi2O6 aegirine structure.

These are all high temperature fluxed or hydrothermal syntheses.

[AndrewLocock]

Can the CsAlSiO4 and CsAlSi2O6 materials be grown as stoichiometric (mm sized) single crystals?  Can they be grown in large enough quantities suitable for global distribution (~100 grams)?   Is this an expensive synthesis?  

I suggest that the compounds CsCoPO4 and TlZnPO4 could be preferable for use as Cs and Tl standards, respectively.

The former has more Cs than pollucite, is insoluble and beam-stable, has no X-ray overlaps among its elements, and can be synthesized as reasonably-sized crystals at <1375 K.
See:  Kawaji, H., Ishihara, Y., Nidaira, A., Tojo, T., Atake, T. and Kuroiwa, Y., 2008. Particle size effect on the new phase transition in a tridymite compound, CsCoPO4. Journal of Thermal Analysis and Calorimetry, 92(2), pp.451-455.

The latter has high Tl content, and is (very probably) insoluble and beam-stable, with no X-ray overlaps among its elements, and can be synthesized as reasonably-sized crystals at <1350 K,
See: Wallez, G., Xuriguera, A.M., Elfakir, A. and Quarton, M., 1993. Crystal growth and crystallographic data of five TIB II XO 4 compounds. Powder Diffraction, 8(3), pp.145-148.

Best regards, Andrew