Comparison of superconducting properties and residual resistivities of bronze processed Nb3Sn wires with Ta, Ti and Ni+Zn additives

Critical current densities up to 23 T measured on a series of 19 core Nb
3
Sn wires with Ta, Ti and Ni+Zn additions, prepared by the bronze route under identical conditions, show very similar results in the whole field range. After optimization, J
c
in the A15 layer was determined to 6 × 10
⁴
A/cm
²
at 18 T, independent on the alloying element. Parallel to the increase of J
c
at high fields, an enhancement of B*
c2
up to 26 to 27 T as well as a reduced strain sensitivity of J
c
with respect to unalloyed Nb
3
Sn wires were observed in all cases. On fully reacted filamentary tapes of
\approx 10 \mu
m thickness and
\approx 100 \mu
m width (obtained from the same starting material) an increase of the residual resistivity from
\rho_{o} = 16 \mu\Omega
cm for binary Nb
3
Sn to 35 - 40 μΩ cm for Ta alloyed Nb
3
Sn (4 at%) was found. The present data are the first direct indication for the increase of ρ
o
in alloyed multifilamentary wires prepared by the bronze route. They furnish a strong evidence for the correlation between ρ
o
and the enhancement of B
c2
in alloyed Nb
3
Sn wires.