Admagistr
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Synthesis of gemstone-chromium doped gallium oxide,color-change at UV
I have synthesized the compound beta-Ga2O3:Cr3+(Ga1.98Cr0.02O3.00) by flame fusion,propane+compressed pure oxygen.Under the same conditions as
ruby.The compound shows a strong alexandrite effect under UV. Gray-green,blue-violet and red color-change.Depends on the intensity and angle of the
incident UV radiation.This compound could be used as a gemstone,I just don't know its hardness,does anyone have access to this information? Gallium is
very related to aluminum,so I decided to make it, like ruby,only with the difference that it is not a corundum type crystal lattice.Corundum type
Ga2O3 can also be made,but under high pressure,which is beyond my capabilities now,if anyone would like to try it,I would be happy to cooperate.I will
send pictures soon!This compound is green and can also be made from melt, based on MoO3,by Verneuil method and other methods used to make rubies.I
used a sapphire crucible made from 99.999% Al203,powdered oxide mixture, Ga2O3 for semiconductors and Cr2O3 spectroscopically pure.I placed the
crucible in a cavity in a chamotte brick.The melting was done with a mini autogenous flame(propane + compressed oxygen.) After the reaction I covered
everything with a chamotte brick.
[Edited on 26-11-2022 by Admagistr]
[Edited on 26-11-2022 by Admagistr]
[Edited on 26-11-2022 by Admagistr]
[Edited on 27-11-2022 by Admagistr]
[Edited on 27-11-2022 by Admagistr]
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clearly_not_atara
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This paper indicates a high hardness for Ga2O3 which is indeed comparable to alumina:
https://par.nsf.gov/servlets/purl/10160736
Generally there isn't much interest in synthetic gemstones, even though practically all jewelry is made of synthetic alloys (native gold is too soft).
[Edited on 04-20-1969 by clearly_not_atara]
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Admagistr
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Thank you very much for this information,what a great gemstone!In my next experiment I will mix this powder precursor with a ruby precursor, 1:1 by
weight.I am curious what properties this crystal will have and if it will crystallize with a corundum crystal lattice or another one.
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Admagistr
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I'm sending some photos, I'll try to take other photos in UV light, but it's hard, the camera show different colors than they actually are, it's
probably not the camera's fault, but a property of chromium doped Ga2O3.
 
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Bedlasky
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Nice work Admagistr!
Alexandrite effect sounds interesting, I didn't know that some other oxides have this property.
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blogfast25
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Quote: Originally posted by Admagistr  | I used a sapphire crucible made from 99.999% Al203,powdered oxide mixture, Ga2O3 for semiconductors and Cr2O3 spectroscopically pure.I placed the
crucible in a cavity in a chamotte brick.The melting was done with a mini autogenous flame(propane + compressed oxygen.) After the reaction I covered
everything with a chamotte brick.
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Pictures would be great.
Also explain a little about "a mini autogenous flame(propane + compressed oxygen.)", please.
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Admagistr
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by Admagistr | I used a sapphire crucible made from 99.999% Al203,powdered oxide mixture, Ga2O3 for semiconductors and Cr2O3 spectroscopically pure.I placed the
crucible in a cavity in a chamotte brick.The melting was done with a mini autogenous flame(propane + compressed oxygen.) After the reaction I covered
everything with a chamotte brick.
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Pictures would be great.
Also explain a little about "a mini autogenous flame(propane + compressed oxygen.)", please. |
In our country, we call this welding machine a mini autogen:
https://www.amazon.de/-/en/Kemper-555K-Autogeen-Hardsoldeert...
It is made in Italy,I used the one with the hottest flame,with a flame temperature of 3300 C.The manufacturer offers three types of gas cylinders,with
different flame temperatures in combination with oxygen.
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blogfast25
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Oh, I see: I speak Dutch; 'autogeen hartdsoldeertoestel'
3,300 C, wow!
Not cheap but not that expensive either...
[Edited on 28-11-2022 by blogfast25]
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Admagistr
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| Quote: Originally posted by blogfast25 | Oh, I see: I speak Dutch; 'autogeen hartdsoldeertoestel'
3,300 C, wow!
Not cheap but not that expensive either...
[Edited on 28-11-2022 by blogfast25] |
I like Dutch,a lot of Dutch people used to come here for holidays in the summer,I even knew a little Dutch,it was in the nineties years.The mini
autogen has the advantage that it is easily portable.Just put it in a backpack,a bigger bag.It has it's use when the reaction releases some harmful
fumes or dust.You can also buy an oxygen bottle from the manufacturer,which can be refilled! I thought of using an oxygen concentrator used by doctors
and physiotherapists as a source of oxygen.A friend has one,so he tried it and it works great! Quite a few people around the world have tried making
rubies with flame,or in a microwave,or electric arc,so they could try gallium oxide instead of alumina. One can also dissolve gallium in HCl and add
some chromium and then precipitate it with alkaline carbonate...Wash the precipitate with distilled water,dry it and use it for the reaction.Gallium
is much more expensive than aluminum,but not so expensive that one can't buy it,at least in small quantities,there are many sellers. I think the
crucible could also be made of corundum ceramic,it does not have to be very pure and expensive sapphire.I bought a sapphire tube,from which I cut the
crucible of the necessary size with a mini diamond wheel,it was very,very expensive,made by the modified Stepanov method in the company Crytur in
Turnov,Czech Republic.
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Admagistr
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I am sending a few more links on the topic. The last seller is my friend,he sells crucibles of corundum ceramics and chemical elements, some compounds
and laboratory equipment,he does not offer to foreign because he is lack of time,but if someone wants to buy something,write me and I will arrange it
with him...
https://www.youtube.com/watch?v=WH_ww_v5Fs0
https://www.crytur.cz/solutions/sapphire-profiles/
https://svetprvku.cz/13-ostatni
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Admagistr
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| Quote: Originally posted by Bedlasky | Nice work Admagistr!
Alexandrite effect sounds interesting, I didn't know that some other oxides have this property. |
Thanks a lot Bedlasky! I also did not know that this compound shows alexandrite effect in UV,it surprised me! I know that some synthetic corundum
produced for this purpose doped with V2O3 and some natural spinels,garnets and the mentioned corundum show weak alexandrite effect,but it cannot be
compared with alexandrite,their color exchange does not reach such qualities.The Alexandrite effect is also caused by the Nd3+ cation, for example
sometimes in the mineral monazite.
[Edited on 29-11-2022 by Admagistr]
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Admagistr
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I mixed 34.86g of Al2O3,64.09g of Ga2O3 and 1.05g of Cr2O3 in order to create a compound
Ga099Al099Cr002O300.Something between ruby and Beta Ga2O3 doped with chromium.
I used a small sample of this mixture. The procedure was the same of melting the mixture of powdered oxides with a flame of autogen with a
temperature of up to 3300 C in a sapphire crucible,which was inserted into a cavity in a chamotte brick.
I was very curious,whether the resulting melt would be red,green,or another color,for example yellow...??
The result of the experiment was a green melt that glowed beautifully red under UV light.Since the mixture was not perfectly homogeneous,traces of
ruby coloring were sometimes produced,but really only traces of a few millimeters.
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