Improved critical current densities in B4C doped MgB2 based wires

TL;DR

Adding 10 wt.% B4C powders to MgB2 wires and heat treating at 800°C significantly enhances their critical current density, making them promising for future superconductor applications.

Contribution

This study demonstrates that B4C doping improves MgB2 wire performance, providing an alternative to SiC with comparable Jc enhancements.

Findings

Jc of 1.10^4 A/cm2 at 4.2 K and 9 T achieved

B4C doping causes lattice constant reduction, indicating carbon substitution

B4C addition yields second highest Jc improvement after SiC

Abstract

An improvement of the transport critical current density, Jc, of MgB2 wires was obtained after addition of 10 wt.% B4C powders, after reaction at 800 C: Jc values of 1.10^4 A/cm2 at 4.2 K and 9T were obtained for wires of 1.11 mm diameter in a Fe matrix. The starting mixture of Mg and B was doped with sub-micrometric B4C, the ratio being Mg : B : B4C = 1: 2 : 0.08, corresponding to 10 wt.% B4C. For T > 800 C, a decrease of Jc was found, due to the reaction with the Fe sheath. In order to investigate the origin of the improvement of the transport properties for heat treatments up to 800 C, X-ray diffraction measurements were performed. A decrease of the lattice constant a from 0.30854 nm to 0.30797 nm was found, thus suggesting an effect of the substitution of Carbon on the properties of the wires. A comparison with the literature data shows that the addition of B4C powders leads to the second highest improvement of Jc reported so far after SiC, thus constituting an alternative for future applications.