SUPRALEITENDE NIOB-GALLIUM-LEGIERUNG

摘要

1409340 Depositing Nb-Ga alloys RCA CORPORATION 25 June 1973 [3 July 1972] 29991/73 Heading C7F [Also in Division H1] A super-conducting article comprises a substrate having a first layer of a Nb-rich Nb-Ga alloy of beta-tungsten structure having a critical temperature of 13-15‹K and a second layer of Nb-Ga alloy of beta-tungsten structure having a critical temperature above 19‹K, the second layer comprising substantially one molecule of Ga to three molecules of Nb. The layers may be deposited by chemical vapour deposition, the first at T>700‹C and the second at 640-700‹C; the substrate may be metal, ceramic, glass or quartz. As shown, He (or Ar) as carrier gas enters tubes 18 and 19, whilst H 2 as reducing gas enters at 14. Halogen-containing gas, e.g. HCl or Cl 2 , is passed over Nb granules 20 and over Ga in boat 21 in relative amounts to produce the required deposition atmosphere, excess gas being fed in at 22 to prevent premature reaction and deposition. With the reactor temperature above 700 C, a first layer, e.g. 3-5Á thick, of Nb-Ga alloy is deposited, then the temperature is lowered to 640-700‹C, and the supply of halogen to the Nb is lowered, and the required second layer is deposited.