Nanoscale-SiC doping for enhancing Jc and Hc2 in the Superconducting MgB2

TL;DR

Nanoscale-SiC doping in MgB2 significantly enhances its critical current density and upper critical field by inducing nano-precipitates and impurity phases, with minimal impact on the critical temperature.

Contribution

This study demonstrates that nanoscale-SiC doping improves superconducting properties of MgB2 through nano-precipitate formation and impurity phases, advancing doping strategies for superconductors.

Findings

Hc2 and H* increased with SiC doping

Jc substantially improved across all fields and temperatures

Nano-precipitates and impurity phases identified

Abstract

The effect of nanoscale-SiC doping of MgB2 was investigated using transport and magnetic measurements. It was found that there is a clear correlation between the critical temperature Tc, the resistivity r, the residual resistivity ratio, RRR = R(300K)/R(40K), the irreversibility field H* and the alloying state in the samples. SiC-doping introduced many nano-scale precipitates, provoking an increase of r(40K) from 1 mW-cm (RRR = 15) for the clean limit sample to 300 mW-cm (RRR = 1.75) for the SiC-doped sample, leading to significant enhancement of Hc2 and H* with only minor effect on Tc. EELS analysis revealed a number of nano-scale impurity phases: Mg2Si, MgO, MgB4, BOx, SixByOz, BC and unreacted SiC in the doped sample. TEM study showed an extensive domain structure of 2-4nm domains induced by SiC doping. The Jc for the 10% nano-SiC doped sample increased substantially at all fields and temperatures compared to the undoped samples, due to the strong increase in Hc2 and H* produced by SiC doping.