GB1077619A - A process for the production of intermetallic superconducting compounds - Google Patents

Abstract

Two component superconducting intermetallic compounds which contain as one component one of the metals vanadium, niobium or tantalum are prepared by contacting in vapour phase and in the absence of oxygen a heat-decomposable organic compound of said one component and a heat-decomposable organic compound of the other component in suitable proportions with a support material heated to a temperature sufficient to decompose said compounds, thereby depositing on said support material a coating containing about 75 atom-% of the metal of said one component and 25 atom-% of the other component and thereafter heating the coated support at 700-1200 DEG C. in vacuo or in a protective gas to form the desired intermetallic compound. The vanadium, niobium or tantalum compound may be e.g. dicyclopentadienyl niobium, dicyclopentadienyl vanadium and dicyclopentadienyl tantalum and dibenzene vanadium and cyclopentadienyl-vanadium tetracarbonyl. The other component may be employed as an alkyl compound e.g. gallium triethyl, gallium n-butyl and tin-tetramethyl and tetraethyl. The compounds may be vaporized outside the reaction zone and conveyed by a carrier gas such as hydrogen, argon and nitrogen into the reaction zone. The support materials may be oxygen-free electrolytic copper, low carbon iron, aluminium, nickel or a steel-nickel alloy containing 10% (by weight) of nickel. Air must be removed from the reaction zone before coating commences by evacuation or replacement with an inert gas. The walls of the reaction zone may be heated to 100-300 DEG C. e.g. by means of an electric furnace or by means of heating liquids such as glycerine or (paraffin oil) passed in tubes around the zone. The support may be in the form of a wire or strip and heated by passage of an electric current or by high-frequency heating. After coating the heating may be for 5 to 20 minutes.ALSO:Two - component superconducting intermetallic compounds which contain as one component one of the metals vanadium, niobium or tantalum are prepared by contacting in vapour phase and in the absence of oxygen a heat-decomposable organic compound of said one component and a heat-decomposable organic compound of the other component in suitable proportions with a support material heated to a temperature sufficient to decompose said compounds, thereby depositing on said support material a coating containing about 75 atom-per cent of the metal of said one component and 25 atom-per cent of the other component and thereafter heating the coated support at 700-1200 DEG C. in vacuo or in a protective gas to form the desired intermetallic compound. The vanadium, niobium or tantalum compound may be, e.g dicyclopentadienyl niobium, dicyclopentadienyl vanadium and dicyclopentadienyl tantalum and dibenzene vanadium and cyclopentadienyl - vanadium tetracarbonyl. The other component may be employed as an alkyl compound, e.g. triethyl gallium, n-butyl gallium and tetramethyl- and tetraethyl-tin. Intermetallic compounds specified include niobium-gallium, niobium-aluminium, niobium-indium, vanadium-tin, tantalum tin and vanadium-gallium. The compounds may be vaporized outside the reaction zone and conveyed by a carrier gas such as hydrogen, argon and nitrogen into the reaction zone. The support materials may be oxygen-free electrolytic copper, low carbon iron, aluminium, nickel or a steel-nickel alloy containing 10% (by weight) of nickel. Air must be removed from the reaction zone before coating commences, by evacuation or replacement with an inert gas. The walls of the reaction zone may be heated to 100-300 DEG C., e.g. by means of an electric furnace or by means of heating liquids such as glycerine or liquid paraffin passed in tubes around the zone. The support may be in the form of a wire or strip and heated by passage of an electric current or by high-frequency heating. After coating the heating may be for 5 to 20 minutes.ALSO:Dicyclopentadienyl - niobium and dicyclopentadienyl-tantalum are prepared by the method of Wilkinson, Cotton and Birmingham (J. Inorg. and Nuc. Chem. (1956) (2, 95-113) from niobium trichloride or tantalum trichloride. These compounds, and others including dibenzene vanadium and cyclopentadienyl vanadium tetracarbonyl, may be used for the thermal deposition of the metal.