Title :
Superconductivity of Nb/sub 3/Al formed by solid state reaction of Nb with Ag-based alloy
Author :
Takeuchi, T. ; Kosuge, M. ; Iijima, Y. ; Inoue, K.
Author_Institution :
Nat. Res. Inst. for Metals, Ibaraki, Japan
fDate :
3/1/1993 12:00:00 AM
Abstract :
It is shown that replacement of bronze with Ag-based solid solution prevents the formation of the ternary compound which corresponds to the mu phase and/or C14 Laves phase in the Cu-Nb-Al system, and thus Nb/sub 3/Al, together with Nb/sub 2/Al, is formed by a solid-state diffusion reaction between Nb filaments and Ag-(2 approximately 15)at.%Al solid solution matrix in the temperature range of 750 approximately 900 degrees C. Metastable Nb/sub 3/Al with high T/sub c/ forms at the early stage of the reaction and decomposes after long heat treatment. The highest T/sub c/ and H/sub c/ (4.2 K) are 13.9 K and 14 T, respectively, for the single-core composite. Since the layer thickness of Nb/sub 3/Al is much less than 1 mu m, a multifilamentary structure that introduces a large number of matrix/core interfaces greatly improves the overall J/sub c/.<>
Keywords :
aluminium alloys; composite superconductors; critical current density (superconductivity); heat treatment; niobium alloys; silver alloys; superconducting critical field; superconducting transition temperature; type II superconductors; 1 micron; 13.9 K; 14 T; 750 to 900 degC; Ag-based solid solution; C14 Laves phase; Cu-Nb-Al system; Nb-Al-Ag; Nb/sub 2/Al; Nb/sub 3/Al; bronze; critical current density; critical field; critical temperature; heat treatment; matrix/core interfaces; metastable; mu phase; multifilamentary structure; single-core composite; solid-state diffusion reaction; Aluminum alloys; Annealing; Copper; Heat treatment; Matrix decomposition; Niobium alloys; Solid state circuits; Superconductivity; Wires; X-ray scattering;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
