Some improvements in laves phase high-field superconductors

Abstract

Improvements in superconducting properties and workability have been achieved both in V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (Hf,Zr) and in V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (Hf,Nb), through the effects of additional elements. The V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (Hf,Zr) can be fabricated into a conductor form by a composite diffusion process in which a composite of vanadium sheath and Zr-Hf alloy core is cold-worked and then heat treated. The addition of hafnium to the vanadium sheath considerably improves the critical current density J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> , and moreover it makes the fabrication of the composite easier by reducing the difference in workability between the sheath and the core. The multifilamentary V-(1-2)at%Hf/Zr-25at%Hf wire may be practically useful for generating magnetic fields up to 15T. The V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (Hf,Nb) ternary alloys containing hafnium less than 17at% can be fabricated by direct plastic deformation at room temperature. The titanium addition to the V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (Hf,Nb) significantly improves both the superconducting properties and the workability. In the cold-rolled V-19at%Hf-6at%Ti-8.3at%Nb, transition temperature T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> of 9.9K, upper critical field H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c2</inf> (4.2K) of about 22T and overall J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (4.2K) of 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 13T are obtained.