coal - 16-11-2007 at 12:47
i need to make a phosphor screen for various electron gun experiments i have planned. i could just cut the front of a small oscilloscope CRT, but
that would be easy, cheating and less fun.
SO
i'm trying to make zinc sulphide phosphor. it was mentioned in another thread that ZnS must be heated in order to change the crystal structure, to
what temperature must this be done for and for how long?
(apparently there is a file on the FTP server, but when i log in (ftp.sciencemadness.org) i just see an empty 'incoming' folder and nothing else)
are there any other fun phosphors i could experiment with whilst i'm at it? obviously i'll try the copper and silver doping of the ZnS as a first
step
any other suggestions or hints welcome 
bilcksneatff - 19-11-2007 at 14:28
According to wikipedia:
"It is typically encountered in the more stable cubic form, known also as the mineral sphalerite. The hexagonal form is also known both as a synthetic
material and as the mineral wurtzite...A transition from the sphalerite form to the wurtzite form occurs at around 1293.15 K."
http://en.wikipedia.org/wiki/Zinc_sulfide
Here's more on phosphors:
"Phosphors are usually made from a suitable host material, to which an activator is added. The best known type is a copper-activated zinc sulfide and
the silver-activated zinc sulfide (zinc sulfide silver).
The host materials are typically oxides, sulfides, selenides, halides or silicates of zinc, cadmium, manganese, aluminum, silicon, or various rare
earth metals. The activators prolong the emission time (afterglow)."
http://en.wikipedia.org/wiki/Phosphors
Hope this helps.
Jamjar - 19-11-2007 at 15:22
Phosphor Handbook By William M. Yen, Shigeo Shionoya, Hajime Yamamoto, Page 598 - Google Books
bilcksneatff - 19-11-2007 at 17:10
See this website.
http://home.earthlink.net/~lenyr/
This guy has homemade CRTs and links to videos of them operating.
coal - 20-11-2007 at 14:25
Thanks for the replys. i feel rather silly now i did check the ZnS and phosphor wiki articles, guess i didn't have my brain switched on :/
the temperatures required seem to be about at the maximum my tube furnace can safely reach, i'll give it a go at some point though
most likely method will be putting a small amount in a closed ended sillica tube with a small strip of graphite sheet to mop up the O2 and a small
ceramic fiber wool plug in the end.
feacetech - 22-11-2007 at 14:57
If you make ZnS from Zn and S, it gets pretty damn hot, hot enough and long enough I dont know.