Study of Ag and Cu / MgB2 powder-in-tube composite wires fabricated by in-situ reaction at low temperature

TL;DR

This study explores low-temperature in-situ reactions to fabricate Ag and Cu sheathed MgB2 superconducting wires, revealing diffusion behaviors and optimizing conditions for high critical temperature and current density.

Contribution

It demonstrates successful low-temperature fabrication of Cu/MgB2 composite wires with high Tc and Jc, highlighting diffusion control and alloying effects.

Findings

Mg diffuses strongly in Ag sheaths, hindering MgB2 formation.

Formation of MgCu2 layer in Cu sheaths stops Mg diffusion.

Optimized Mg excess yields Tc=39 K and good Jc in Cu/MgB2 wires.

Abstract

Superconducting Ag or Cu sheathed MgB2 wires have been fabricated by conventional powder-in-tube techniques. The in-situ reaction of Mg and B powders with atomic proportions of 1:2 and 1.33:2 inside Ag or Cu tubes at low temperatures have been searched. An active alloying of Mg with Ag or Cu sheaths at temperatures below 660 C has been observed. For Ag sheaths, there is a strong diffusion of Mg, which does not allow the formation of large amounts of MgB2 at the core. For Cu sheaths, the diffusion of Mg is stopped by the formation of a MgCu2 layer around the superconducting core and an appropriated excess of Mg leads to superconducting cores with Tc=39 K and good Jc values, thus being possible the development of Cu/MgB2 composite wires.