Chemical
IDEAS
Liquid Laser Soup. Back in '63, our people in the General Telephone & Electronics labs got the first liquid laser to lase. T h e new laser was based on a chelate structure con sisting of a europium ion sitting in the middle of a cage formed by four benzoylacetonate ligands. These mole cules, like rambling jailhouses, floated in a solvent which was a mixture of ethyl and methyl alcohols. T h e n we started to improve the soup. T h e europium ion eventually gave way to neodymiurn, which does such a smashing job in solid lasers. B u t the real breakthrough came in finding a solvent t h a t would plop excitation energy into the N d + + + ion and not dis perse 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 shozvn as dipoles.
I t turns out t h a t 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 neodym ium, it helped outclass the original chelate laser by 1000 times in light o u t p u t and 10,000 times in efficiency. All this leads up to a recent development. It's neodymium-doped phosphorus oxychloride (POCb).
SYLVANIA GENERAL TELEPHONE & ELECTRONICS
This laser liquid is totally free of hydrogen ions. I t ' s also free of suspended m a t t e r . You know how a laser beam sparkles and twinkles in t h e 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 t h a n 2 microns. We handle it in a sealed system to keep out airborne j u n k and water vapor. We price it at over $500 per liter. Which shows how valuable it is to know about rare earths, phosphors, inorganic complexes and all t h a t kind of stuff.
Metallic, but not quite metal. Question: W h a t substances look like metals and act like metals b u t are really chemical compounds? Answer: T h e tungsten bronzes. Consider their subtly misleading general formula: MxW03. You'd expect χ to be a whole number. D o n ' t bet on it. T h e χ is a fraction t h a t ' s less t h a n one. In a compound like sodium tungsten bronze (NaxW03) it runs from Ό25 or less to 0.9. Which means t h a t the M component com bines with t u n g s t a t e ions non-stoichiometrically. T o the eye it means t h a t as sodium content goes up, the color of the bronze goes from red-purple to goldenyellow. T h e surface retains its beautiful metallic sheen. T h e bronzes are insoluble in water, acids, and common solvents. Although they strongly resent oxidation, they are readily oxidized in an alkaline medium. T h a n k s 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. ( F u n n y thing, though, C u x W 0 3 and A g x W 0 3 are semiconductors — as are sodium tungsten bronzes with χ less t h a n about .25.) With their high conductance and high chemical re sistance, it seems n a t u r a l to recommend them as elec trodes. 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 in sulating 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 b u t us tungsten boys should research them?). If we tapped a vein of real interest, we could get serious. N o samples. N o d a t a sheets. But lots of encouragement if you w a n t 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 10 C&EN
