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Author: Subject: Making phosphorescent materials
beta4
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[*] posted on 3-2-2019 at 06:53
Making phosphorescent materials


Hi everyone, long time forum reader here that just registered.

I'm writing this post to share the success I've had in making ZnS:Cu, or copper doped zinc sulfide.
It's a phosphor that emits a green light when excited with UV light or an electron beam.

The preparation procedure is here (yes, yet another youtube channel)

https://www.youtube.com/watch?v=NGdVCIGHeQE

Perhaps even more interesting, the preparation procedure that I followed is documented in the book "Inorganic Phosphors" by W. Yen and M. Weber. The book is quite dry, resembling more a lab notebook, but it contains hundreds of phosphor recipes, and hasn't been mentioned on this forum yet.
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XeonTheMGPony
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[*] posted on 3-2-2019 at 07:35


Very nice video, guy deserves more subs, look forward to see what he does with it.
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fusso
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[*] posted on 3-2-2019 at 09:01


GREAT setup for heating small amount of stuff in inert atmosphere!



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[*] posted on 3-2-2019 at 15:22


I'm glad you liked the video, XeonTheMGPony.
I'm currently waiting for some ITO coated conductive glass to arrive from china. When it arrives, I'll try to make a small EL display and see how it goes.

fusso, the tube furnace is a design of mine. I've taken inspiration from Doug's Lab furnace, but one main requirement was minimizing cost. To be honest, I wasn't sure I'd be able to make something as sensitive to impurities as a phosphor, so I was looking for a cheap feasibility check.
Just some more info if someone wants to replicate my setup: I bought 5 quartz tubes from deschem for ~20€, enough fire bricks to make four of these furnaces for another 5€, and the argon cylinder and regulating valve for 20€ each. I already had the gas torch.
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CharlieA
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[*] posted on 3-2-2019 at 16:49


If I ever get a "round-2-it", I may try making some to dope alumina or silica gel plates for TLC. Thanks for the link. Charlie
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XeonTheMGPony
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[*] posted on 4-2-2019 at 04:56


What was the IR sensitive phosphor they used for testing remote control IR transmitters?
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[*] posted on 4-2-2019 at 12:45


I recall that some long afterglow phosphors can be "charged" with UV light, and be made to release the stored energy and light up under IR light.
The book I referenced lists one such phosphor: ZnS:Pb,Cu
The preparation is very similar to the one in my video (inert atmosphere, 1100°C firing temperature), but requires to add ~1.65mg of lead nitrate instead of the ammonium chloride.

I also found (in the same book) a few "upconversion" phosphors able to convert infrared to visible, but don't seem very amateur friendly to make. One is made of 25% molar ErCl3, the rest being BaCl2, but is hygroscopic and destroyed by moisture. The others are even worse as are based on fluorides.


[Edited on 4-2-2019 by beta4]
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[*] posted on 4-2-2019 at 13:03


Interesting stuff, that. I've attached a .pdf demonstrating the properties of commercial pumped IR phosphors. It doesn't provide any compositional information, but does show what you can get out of them. Also, they rotate the stuff in the beam to minimize saturation.

O3

Attachment: Low-Cost IR Visualizer.pdf (416kB)
This file has been downloaded 131 times





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[*] posted on 7-2-2019 at 15:40


Great results!
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Bezaleel
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[*] posted on 13-2-2019 at 11:22


Thanks for posting this!

I wonder why the argon shield works at all, because I would think that through diffusion, the argon will escape. That the argon is heavier than air doesn't matter too much when it comes to inhibiting diffusion. At least, that's my experience with diffusion. (And I didn't see you close the ends of the tubes attached to the quartz heating tube.)

Does it boil down to a matter of good timing? I.e. the diffusion speed being slow enough to allow for 10 minutes of heating without the copper oxidising?
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[*] posted on 13-2-2019 at 12:07


From what I read, doping of crystalline materials is affected by the atmosphere used during the reaction.

In the phosphors book, each phosphor recipe includes an atmosphere recommendation.
Some recipes just say to do the firing in air, so I guess that if any other atmosphere is recommended, there has to be a reason.
However, it may not mean that it absolutely does not work unless the proper atmosphere is used.

This leaves two possibilities:
- either the small openings of the tube coupled with the fact that the firing is done immediately after the Ar filling limits diffusion
- or a little bit (or a lot) of air does not affect the preparation of ZnS:Cu
- or both

To know for sure we need a phosphor that absolutely does not work when fired in air, but works when fired with the tube filled with Ar in the way I've done so far.

I may have a good candidate, but no promises on when I can do the tests (I'm busy with my day job).
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[*] posted on 13-2-2019 at 12:34


Very nice video!

I do think you are a bit hard to understand when you are standing in a certain position compared to your camera, sometimes it is fine, sometimes you sound different. It may be worse when you stand behind your camera, or maybe it is the distance.

But keep up the videos, I at least subscribed.
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