Accession Number : AD0680767

Title :   OXIDATION RESISTANCE AND SEMICONDUCTIVITY OF A TUNGSTEN FLUORIDE OF LOW FLUORINE CONTENT,

Corporate Author : AEROSPACE CORP EL SEGUNDO CALIF LAB OPERATIONS

Personal Author(s) : Siegel,Bernard ; Johnson,Richard L. ; Marx,Paul

Report Date : NOV 1968

Pagination or Media Count : 17

Abstract : It is shown that at elevated temperatures, a tungsten fluoride of low fluorine content (WF(0.31)) is considerably more resistant to oxidation than the pure metal. This is attributed to the electrostatic repulsion of attacking oxygen species by the fluoride bonds. Unlike gaseous fluorides, which require complete geometrical shielding of the central atom of each fluoride molecule for effective oxidation resistance, a relatively small ratio of fluorine-to-metal atoms suffices in the crystalline state. It is suggested that the fluorines in the crystalline compound must be situated in strategic sites, either by a complete screen of chemisorbed metal-fluorine bonds at the grain boundary surfaces, or by substitutional bonds in the lattice. The WF(0.31) compound is shown to be nonhomogeneous. Ten percent of the compound was an imperfectly crystalline tungsten monofluoride, which oxidized readily; the remaining 90 percent was WF(0.24), which is shown to be the oxidation-resistant component. It is also shown that WF(0.31) and an analogous group VI-A compound (MoF(0.47) are semiconductors, with specific conductivities at room temperature of 0.0000258 and 0.00000213 reciprocal ohm-cm, respectively. Both of these fluorides can be prepared by metal explosion reactions. (Author)

Descriptors :   (*TUNGSTEN COMPOUNDS, OXIDATION), (*SEMICONDUCTORS, TUNGSTEN COMPOUNDS), FLUORIDES, SYNTHESIS(CHEMISTRY), CRYSTAL DEFECTS, CRYSTAL LATTICES, SURFACE PROPERTIES, CHEMISORPTION, ELECTRICAL CONDUCTIVITY, DOPING, EXPLODING WIRES

Subject Categories : Physical Chemistry
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE