What is the best crucible for induction melting PGM's?

If the quantity is small, you can get away with alumina. Pd must of course be melted under argon, CO2, or vacuum.
How long the crucible lasts is contingent on many things, notably the presence (or lack) of fluxing agents.

No, the yttria-stabilized zirconia crucible is loaded with sponge, covered temporarily and put inside of or nested in the alumina crucible and that is loosely filled with zircon sand around the zirconia crucible. I was not clear about what I said and will edit it accordingly, my apologies. The sand is just used to insulate the alumina from the intense heat and act as a cushion for expansion and contraction. You need not do any of that.

Don't worry about metal compatibilities because you were already advised not to melt PGMs in metal (excluding a water-cooled copper hearth).

I do not roll Ir (not exactly easy for anyone, look at its bulk modulus). Most Ir crucibles are electroformed from molten cyanide baths via a proprietary, nasty technology by JM. If not done that way, they are electron beam welded together. I don't do any of that, only very occasionally melt the pure metal and what little experience working it I have makes me shudder.
I do see used crucibles from time to time, how big do you need (liter, 10 liter, bigger?).

I would like some sapphire windows preferably in a specific arrangement for a project I am working on where I need to continuously take a reading on a high pressure abrasive slurry.

Morgan Technical CeramicsIf the quantity is small, you can get away with alumina. Pd must of course be melted under argon, CO2, or vacuum.How long the crucible lasts is contingent on many things, notably the presence (or lack) of fluxing agents.No, the yttria-stabilized zirconia crucible is loaded with sponge, covered temporarily and put inside of or nested in the alumina crucible and that is loosely filled with zircon sand around the zirconia crucible. I was not clear about what I said and will edit it accordingly, my apologies. The sand is just used to insulate the alumina from the intense heat and act as a cushion for expansion and contraction. You need not do any of that.Don't worry about metal compatibilities because you were already advised not to melt PGMs in metal (excluding a water-cooled copper hearth).I do not roll Ir (not exactly easy for anyone, look at its bulk modulus). Most Ir crucibles are electroformed from molten cyanide baths via a proprietary, nasty technology by JM. If not done that way, they are electron beam welded together. I don't do any of that, only very occasionally melt the pure metal and what little experience working it I have makes me shudder.I do see used crucibles from time to time, how big do you need (liter, 10 liter, bigger?).I would like some sapphire windowspreferably in a specific arrangement for a project I am working on where I need to continuously take a reading on a high pressure abrasive slurry.

If you want to learn more, please visit our website Graphite Crucible for Sale.

Contact us to discuss your requirements of graphite block for sale. Our experienced sales team can help you identify the options that best suit your needs.

The company is the world’s best graphite blocks for casting supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.