Superconducting Properties of ${\rm Nb}_{3}{\rm Sn}$ Wire Fabricated by Diffusion Reaction Between Ag-Sn-Mg Alloy and Nb

Mg addition improves
T

_c
,
B

_irr
, and
I

_c
of the Nb
₃
Sn formed by diffusion reaction between Nb and Ag-Sn alloy, when the diffusion reaction is performed below 650
^deg
C. The obtained superconducting properties are similar to those of the bronze-processed Nb
₃
Sn. The formation temperature of Nb
₃
Sn is reduced by the Mg addition. By using OM, SEM, and field emission type EPMA, we could not measure the thickness of Nb
₃
Sn layers, which may be thinner than 0.5 mum. It is not clear that the Mg addition increases the formation rate of Nb
₃
Sn. However, the Nb
₃
Sn layers should have very high
J

_c
. The attainable overall
J

_c
of the Nb
₃
Sn wire are as high as those of the bronze-processed Nb
₃
Sn wire without Ti and Ta additions, although the optimization of the cross-sectional configuration of Nb and Ag-Sn-Mg in the wire has not yet performed. Therefore the potential of the Nb
₃
Sn conductor made by the new process seems to be very attractive for the practical applications.