Microstructure and high critical current of powder in tube MgB2

TL;DR

This study demonstrates that heat treatment of powder-in-tube MgB2 wires significantly enhances their critical current density by reducing micro-cracks and eliminating weak links, leading to improved superconducting performance.

Contribution

It introduces an effective heat treatment process that improves microstructure and critical current in MgB2 wires fabricated via powder-in-tube method.

Findings

Jc increased by over an order of magnitude after annealing

Micro-cracks were eliminated through heat treatment

Weak-link behavior was reduced, enhancing superconductivity

Abstract

We report dc transport and magnetization measurements of Jc in MgB2 wires fabricated by the powder-in-tube method, using commercial MgB2 powder with 5 %at Mg powder added as an additional source of magnesium, and stainless steel as sheath material. By appropriate heat treatments, we have been able to increase Jc by more than one order of magnitude from that of the as-drawn wire. We show that one beneficial effect of the annealing is the elimination of most of the micro-cracks, and we correlate the increase in Jc with the disappearance of the weak-link-type behavior.