Materials with consistent cathodoluminescence intensity

[anenburg]

I'm thinking about making some materials with consistent cathodoluminescence intensities, ideally single crystals using a flux melt.
Some things I was thinking about was titanates (BaTiO3, SrTiO3, BaTaSi3O9 aka benitoite), and maybe also zirconates (BaZrSi3O9?).

The only important things are that it has intrinsic cathodoluminescence with little influence from trace elements so can be prepared again and get the same CL intensity, somewhat easy to grow to largish (0.5–1 mm) crystals, and cathodoluminescence stays constant and does not degrade or change over time under beam exposure.

Does anyone have some experience or ideas?

[crystalgrower]

General question about cathodoluminescent  (CL) materials.  Has anybody got a good CL-specific review article that cites direct comparisons of three prep methods—fluxed growth, hydrothermal growth and crystallization from melt (Verneuil or Czochralski)? And then there are the practical details.

The worst issue with fluxed growth is getting ALL the flux off the crystals. This means some furnace modification to safely invert the crucible at growth temperature, plus reheating the crystals on a mesh to melt off more flux, and finally boiling off the residue.  Very long and might not be good enough for CL.

Both former and current commercial production of single crystals use the Verneuil or Czochralski method with no flux (no cleanup). The second advantage of melt growth is that the orientation is well defined for a large area.  For some materials including SrTiO3, control of the atmosphere is  also essential (see Wikipedia article).

Melt growth is best done on a commercial scale but the price for materials without doping is reasonable.  One modification is called micro-pulldown which requires smaller furnace setup. The only limitation is the requirement that no phase transitions occur  during cooling (growing many fluorides would not work).

This link  is one current source with comprehensive details (although they misspell Verneuil) https://www.crystalsubstrates.com/en-ca/products/strontium-titanate-srtio3-substrates

Their price for small cuts is low enough to just get a set and start testing.  Ask them for a price quote for thicker slices or even an uncut boule (50-100g of consistent material) which would be a one-time purchase.   

And for benitoite, old natural specimens had a blue (trace Fe) phase next to a colourless phase which might still be BaTiSi3O9.  I have scraps, ~20 grams,  if you want to do the workup.