Effects of third-element additions on the superconducting properties of bronze-processed V3Ga wires

The effect of In, Zn, and Mn additions to the bronze matrix on formation rate, critical current density, and critical temperature of V
3
Ga layers in bronze-processed V
3
Ga wires has been investigated. The V
3
Ga layers were produced by heat treatment at 600...650 °C within a period of 20... 200 h. For a given heat treatment condition the critical current density (j
c
) of the V
3
Ga phase and the critical current (I
c
) of In-containing conductors with a suitable composition of bronze (e.g. 16 at.% Ga, 1.2 at.% In) are considerably higher (by the factor ≥ 1.7) than those of conductors with a usually applied, binary Cu-Ga alloy containing 19 at.% Ga. The critical temperature of In-containing samples is relatively high and approaches values up to 15.4 K (for which the specimens showed half its normal-state resistance). Too high Ga and In contents of the matrix are unfavourably for obtaining high critical parameters. An addition of Mn (0.6 at.%) to the bronze leads to considerably thicker V
3
Ga layers, however j
c
and T
c
(down to 13 K) are decreased and thus, depending on theat treatment conditions and Ga content of bronze, unchanged or reduced I
c
values were obtained. Substitution of Zn for 2 at.% Ga in the matrix causes a reduction of V
3
Ga layer thickness and an increase of j
c
.