Fabrication superconductors

The above CVD techniques have been widely applied and used to fabricate superconductor wires and interphase layers for fibre-reinforced metal- and ceramic- matrix composite materials. 

Electrical and Electronic Applications. Silver neodecanoate [62804-19-7] has been used in the preparation of a capacitor-end termination composition (110), lead and stannous neodecanoate have been used in circuit-board fabrication (111), and stannous neodecanoate has been used to form patterned semiconductive tin oxide films (112). The silver salt has also been used in the preparation of ceramic superconductors (113). Neodecanoate salts of barium, copper, yttrium, and europium have been used to prepare superconducting films and patterned thin-fHm superconductors. To prepare these materials, the metal salts are deposited on a substrate, then decomposed by heat to give the thin film (114—116) or by a focused beam (electron, ion, or laser) to give the patterned thin film (117,118). The resulting films exhibit superconductivity above Hquid nitrogen temperatures. 

R. Chevrel, in Superconductor Materials Sciences Metallurgy, Fabrication and Applications (S. Foner, B.B. Schwarz, eds.), Chap. 10. Plenum Press, 1981. 

Several serious problems must be surmounted before applications of high-temperature superconductors can become a reality. Presently known ceramic superconductors are brittle powders with high melting points, so they are not easily fabricated into the wires and coils needed for electrical equipment. Also, the currents that these materials are able to carry at 77 K are still too low for practical applications. Thus, applications are likely in the future but are not right around the corner. 

We fabricated simultaneously a series of Nb-Au bilayers, with a fixed Nb thickness and a varying Au thickness, on a single (6 x 40 mm2) Si substrate. The Nb layer thickness was chosen to be significantly larger than the coherence length s in order to avoid any effect due to the finite thickness of the superconductor. For varying the Au thickness, another Si wafer was used as a mask and moved in situ above the Si substrate. After depositing the 120 nm Nb film, the Au film (from 10 to 260 nm) was deposited within 15 minutes at a pressure below 10-8 mbar. These conditions minimize the interface contamination and should preserve the best Nb-Au interface transparency. The full Si wafer with the bilayer films thus obtained (see Fig. 4a) was cleaved in air to separate the different samples. Individual Au (260 nm) and Nb (120 nm)... 

Technology as we have witnessed over the years has been outpacing any other development. Some of the developments in technology such as co-extrusion in copper, sintered material objects of required shapes, use of thin-film techniques to produce a tape for electrical connections and the fabrication of tapes and wires of superconductor Nb3Sn lend hope for future technological developments in superconducting rare earth materials such as borocarbides and YBaaCujOy. 

Pulsed laser ablation has been developed in many fields for the fabrication of thin films of oxide materials, in particular high Tc cuprate superconductors. In these materials, the increase of the carrier concentration can be obtained in many cases by chemical doping (cationic or anionic), in order to induce superconductivity. 

Some scientists have foregone the ceramics altogether and attempted to fabricate wire out of metal alloys that can superconduct at temperatures warmer than normal for a metal. At the Massachusetts Institute of Technology, for example, one team has made a superconductor from europium—a soft, silvery metal that was once in short supply but is now more easily acquired—barium, and copper. The alloy apparently works well at 90° K, which means it can run on liquid nitrogen moreover, it is more easily fabri-... 

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