Processing of β-W Type Structure Superconducting Compound Materials

Abstract

This article is a survey of the processes for making β-W type structure superconducting compound materials. These processes are classified as follows:
(1) Diffusion process: V₃Ga is easily formed by a improved diffusion technique at 700°C. Nb₃Sn and V₃Si are formed by the diffusion treatment around 950°C while the formation of Nb₃Ga and Nb₃Al requires much higher diffusion temperatures.
(2) Chemical vapour deposition process: Nb₃Sn, V₃Si and Nb₃Ga are deposited by the hydrogen reduction of mixed chloride gases of the constitutional elements.
(3) Vacuum vapour deposition process: Nb₃Sn is made by the simultaneous vapour deposition of Nb and Sn in high vacuum. Processing of high T_c compound Nb₃(Al_0.8Ge_0.2) is also being studied.
(4) Plasma spray process: Nb₃Sn coil can be made directly by this process without wire windings.
High field superconducting Nb₃Sn tapes have already been made commercially by the process (1) and (2). V₃Ga tape also seems to be promising for practical use.