Alright this one's a bit out there. I've been reading up on the Czochralski process that is used to make ruby and stumbled upon a youtube video of a machine that makes it In the video they use a crucible made of yttrium metal which is quite unusual. I'm unsure why they need a yttrium crucible versus a graphite crucible, perhaps it doesn't dissolve into the ruby? The process itself doesn't seem terribly difficult to do at home (there are plenty of other youtube videos of random people making low quality clouded ruby in their garages with arc welders and what not) and may be a fun long term project to replicate with kanthal elements instead of an induction furnace like in the video. The temperature range they use is about 2200F which is easily within range. I see the metal itself isn't terribly expensive on ebay. I wonder if it would be possible to buy some and cast it into a small crucible? What do you think? Possibly using an oxy acetylene torch and a ceramic shell mold?
They may have been growing the common laser crystal: yttrium aluminium garnet rather than ruby. They were careful to completely vacuum the apparatus with a high quality vacuum if they were using ion and pirani vacuum gauges before using an inert gas cover, so it's possible yttrium will ignite and burn like magnesium. Looks like it burns well:
They're not making ruby. Aluminum oxide (ruby) melts at 3762°F, yttrium melts at 2779°F. For a yttrium based crucible, best bet is pre-oxidised: yttrium oxide, yttria. Melting point is 4397°F. Not electrically conductive, so need to work around if using induction melter. I have one crucible of Y2O3 I've been saving in case I decide to try casting steel some day. It's volume is only 20 cc or so. The way I would do it is put my induction melter in a glove box, flow argon into the box, do the melt in the yttria crucible inside a graphite crucible. (I don't think my melter will heat steel much over the curie point; graphite keeps on going.)
