daragh8008
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Sintering Cu2O
Hi Folks,
just wondering if anyone knows about sintering Cu2O. I have been searching for a few day now and I can't seem to find any info/papers on pressing and
sintering Cu2O ceramics. Prehaps it is because it such an old semiconductor or maybe its just not done. I thought it was used in ceramic as a
sintering aid so I thought someone might have studied the sintering behaviour of pressed Cu2O pellets or the like but I can't find anything. Any help
greatly appreciated.
Thanks
PS if this should be in the references section apologies but I don't have access. Also just the citations required as I should have access.
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12AX7
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Hmm, I don't have any experience myself, but I know Cu2O is about as regular as an oxide can get -- it'll work, give it a try?!
I will note that, of course, since copper is a noble metal, its oxides are sensitive to oxygen (or its absence). Depending on what kind of
semiconductor you're looking for, you'll need a neutral or oxidizing furnace atmosphere to do the sintering. (Or you may need a slightly reducing
atmosphere for the other direction, but be careful with that: even a little may result in Cu(0) inclusions or something like that. In the chemistry
of pottery glazes, copper oxide is well known to be readily reduced to microscopic copper spherules, which give a deep red color! Achieving a bright
green (Cu(II)) glaze requires an oxidizing atmosphere.)
Pure Cu2O melts around 1229C, CuO around 1192C, and copper (metal) at 1084C. Practical sintering can typically be achieved starting at around half
the absolute melting point, or ~400C, and gets faster from there until it melts.
Molten copper has about 2.5%wt solubility for Cu2O (and, as far as I know, solubility for O2 gas as well -- which I suspect is independent of the
presence of Cu2O) at a temperature of 1229C. Molten Cu and Cu2O are immiscible until 1335C (at which point any mixture of Cu and O, given sufficient
pressure of course, is a fully liquid solution). This information might be helpful for doping or liquid-phase sintering, but if you're interested in
semiconductor use, you probably need something with much better impurity than a liquid-phase sintering process can offer.
If you want single crystals, you might consider a solution growth process. I would suppose growth from a Cu or CuO solution is undesirable given the
imbalance, and I would suppose growth from an aqueous solution (e.g., very gradual reduction of a Cu(II) solution, resulting in the precipitation of
Cu2O crystals) would be undesirable due to the presence of obdurated H2O. That said, there are likely many other solvents which would serve. There
may only be a few which don't interfere as dopants. Of course, if you're really set on it, the Czochralski process should do a fine job.
Tim
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daragh8008
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Thanks Tim, some very useful info in there. I didn't realise that the sintering could be done at such a low temperature. Came across one paper where
they sintered at a couple of hundred degrees and Just assumed that this wouldnt do a great job in making it a fully dense ceramic. I'm looking for an
alternative to oxidising Cu plates. As the warpage induced means alot of time spent grinding and polishing the surfaces to make it flat. Typically the
polishing cracks about 50% of my samples, that in combination with the oxidising time makes this a very long a labour intensive process. I ordered a
2cm 47 tonne die to try this out. I would imagine this is probable a bit of overkill but better to over spec than to find out that it's too little. As
for atmospheres I have limited options, air vacuum or pure oxygen but at the right temperature aka around 1050c the phase diagram would suggest that I
end up with cu2o. But as you say the only way to find out is to give ita go.
Thanks
Daragh
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Texium
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Thread Moved
20-11-2023 at 12:43 |
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