Chemical
ÎTïratë
Liquid Laser Soup. Back in '63, our people in the General Telephone & Electronics labs got the first liquid laser to lase. The new laser was based on a chelate structure consisting of a europium ion sitting in the middle of a cage formed by four benzoylacetonate ligands. These molecules, like rambling jailhouses, floated in a solvent which was a mixture of ethyl and methyl alcohols. Then we started to improve the soup. The europium ion eventually gave way to neodymium, which does such a smashing job in solid lasers. But the real breakthrough came in finding a solvent that would plop excitation energy into the N d + + + ion and not disperse it uselessly while the neodymium was trying to give birth to a photon.
Solvation shell around a rare earth ion acts pretty much like a chelate cage. Here the inorganic solvent molecules are shown as dipoles.
It turns out that solvents containing hydrogen drain energy out of the N d , because the active, lightweight H + ions (protons) frivolously waggle it away. We looked for an aprotic solvent (which eliminated most organic solvents) and finally came up with selenium oxychloride (SeOCte). When it was spiked with neodymium, it helped outclass the original chelate laser by 1000 times in light output and 10,000 times in efficiency. All this leads up to a recent development. It's n e o d y m i u m - d o p e d p h o s p h o r u s o x y c h l o r i d e (POCb).
SYLVANIA GENERAL TELEPHONE & ELECTRONIC S
This laser liquid is totally free of hydrogen ions. It's also free of suspended matter. You know how a laser beam sparkles and twinkles in the air. This merry sight is due to the light beam's banging into floating dust and dirt. N o such shenanigans can take place in our laser liquid. We filter it with care to remove any particles larger than 2 microns. We handle it in a sealed system to keep out airborne junk and water vapor. We price it at over 2500 per liter. Which shows how valuable it is to know about rare earths, phosphors, inorganic complexes and all that kind of stuff.
Metallic, but not quite metal. Question: What substances look like metals and act like metals but are really chemical compounds? Answer: The tungsten bronzes. Consider their subtly misleading general formula: MxW03. You'd expect x to be a whole number. Don't bet on it. The x is a fraction that's less than one. In a compound like sodium tungsten bronze (Na x W03) it runs from .025 or less to 0.9. Which means that the M component combines with tungstate ions non-stoichiometrically. T o the eye it means that as sodium content goes up, the color of the bronze goes from red-purple to goldenyellow. The surface retains its beautiful metallic sheen. The bronzes are insoluble in water, acids, and common solvents. Although they strongly resent oxidation, they are readily oxidized in an alkaline medium. Thanks to clouds of electrons buzzing around in them, the tungsten bronzes conduct electricity like crazy. One conduction electron is present for every N a atom in the crystalline cell. (Funny thing, though, Cu x W03 and A g x W 0 3 are semiconductors—as are sodium tungsten bronzes with x less than about .25.) With their high conductance and high chemical resistance, it seems natural to recommend them as electrodes. You can dunk them into all kinds of solutions. Use them, for example, as electrodes in fuel cells. You can flash tungsten bronzes on glass or other insulating materials to form thin conductive coatings. Or make thin-film optical filters and reflectors. Even cut gemstones out of single crystals to make jewelry. Polishing our abilities in the bronzes has been a labor of love up till now (who else but us tungsten boys should research them?). If we tapped a vein of real interest, we could get serious. N o samples. N o data sheets. But lots of encouragement if you want to talk to us.
We're always glad to talk to you about tungsten, molybdenum and phosphor chemistry. Sylvania Precision Materials, Chemical and Metallurgical Division, Towanda, Pa. 18848 56 C&EN
