Enhancement of functional properties of V$_{0.6}$Ti$_{0.4}$ alloy superconductor by the addition of yttrium

TL;DR

This study demonstrates that adding yttrium to V$_{0.6}$Ti$_{0.4}$ alloy superconductors creates precipitates and disorders that enhance flux pinning, increasing critical current density especially at 2 at.% yttrium.

Contribution

It reveals how yttrium addition affects precipitate formation and flux pinning, improving the superconductor's performance.

Findings

Yttrium precipitates vary in size and depend on yttrium amount.

Critical current density peaks at 2 at.% yttrium, over 7.5 times the parent alloy.

Superconducting transition temperature increases with yttrium addition.

Abstract

We show here that the yttrium is immiscible and precipitates with various sizes in the body centred cubic V$_{0.6}$Ti$_{0.4}$ alloy superconductor. The number and size of the precipitates are found to depend on the amount of yttrium added. Precipitates with various sizes up to 30~$\mu$m are found in the V$_{0.6}$Ti$_{0.4}$ alloy containing 5 at.\% yttrium. The large amount of line disorders generated by the addition of yttrium in this alloy are found to be effective in pinning the magnetic flux lines. While the superconducting transition temperature increases with the increasing amount of yttrium in the V$_{0.6}$Ti$_{0.4}$ alloy, the critical current density is maximum for the alloy containing 2 at. \% yttrium, where it is more than 7.5 times the parent alloy in fields higher than 1~T. We found that the effectiveness of each type of defect in pinning the flux lines is dependent on the temperature and the applied magnetic filed.