Superconductivity in V$_{1-x}$Zr$_x$ alloys]{Evolution of high field superconductivity and high critical current density in the as-cast V$_{1-x}$Zr$_x$ alloys

TL;DR

This study investigates the structural, electrical, and magnetic properties of V$_{1-x}$Zr$_x$ alloys, revealing how phase composition and microstructure influence superconductivity and critical current density, with implications for optimizing high-field superconductor performance.

Contribution

It provides new insights into how alloy composition and eutectic microstructure affect superconductivity and flux pinning in V-Zr alloys, guiding improved superconductor design.

Findings

Alloys exhibit multiple phases depending on Zr content.

Superconductivity observed below 5.3 K and 8.5 K for specific phases.

High critical current density achieved in V-rich alloys with x > 0.1.

Abstract

We report here the structural, electrical and magnetic properties of as-cast V$_{1-x}$Zr$_x$ alloys ($x$ =0 - 0.4) at low temperatures. We observe that all the alloys undergo successive peritectic and eutectic reactions during cooling from the melt which leads to the formation of five phases, namely, a body centred cubic $\beta$-V phase, two phases with slightly different compositions having face centred cubic ZrV$_2$ structure, a hexagonal closed packed $\alpha$-Zr phase, and the $\beta$-Zr precipitates. The amount of each phase is found to be dependent on the concentration of zirconium in vanadium. The $\beta$-V and ZrV$_2$ phases show superconductivity below 5.3~K and 8.5~K respectively. We show that the critical current density is large for V-rich V$_{1-x}$Zr$_x$ alloys with $x >$ 0.1. The grain boundaries generated from the eutectic reaction, and the point defects formed due to the variation in the composition are found to be responsible for the pinning of flux lines in low and high magnetic fields respectively. Our studies reveal that the choice of the composition and the heat treatment which leads to eutectic reaction are important in improving the critical current density in this alloy system.