The effect of ternary additions to Nb3Sn on the upper critical field at 4.2K

The effect of ternary additions of Group III
b
-IV
b
metallic elements (Al,Ga,In, Tl,Pb) to Nb
2
Sn on the upper critical field H
c2
(4.2K) has been studied. Samples were prepared by arc melting in an argon atmosphere. The measurements of H
c2
(4.2K) were performed with a pulsed magnet, and the value of H
c2
was determined from measurements of the electrical resistivity. H
c2
(4.2K) of the Nb
3
Sn compounds was observed to increase by about 70 KG to a maximum of 300 KG through the replacement of several percent of the Sn by Group III
b
-IV
b
metallic elements. Of these systems, Nb
3
(Sn-In) and Nb
3
(Sn-Pb) were also prepared by the diffusion method: Cold-rolled tapes of Nb doped with the third element were immersed and heat treated in a Sn bath or a Cu-30wt%Sn bath. H
c2
as high as 270 KG was achieved for the Nb
3
(Sn-In) tape prepared in the Cu-30wt% Sn bath at a reaction temperature of 850°C. The critical current of this tape was substantially higher than that of the standard Nb
3
Sn tape in a high field region.