Role of Carbon in Enhancing the Performance of MgB2 superconductor

TL;DR

This paper investigates how carbon doping, including nano-SiC addition, improves the superconducting properties of MgB2 by enhancing critical current density and critical fields through internal and extrinsic pinning mechanisms.

Contribution

It provides a comparative analysis of carbon substitution and nano-SiC addition, revealing their effects on MgB2's superconducting performance and pinning mechanisms.

Findings

Carbon substitution induces disorder and acts as internal pinning centers.

Nano-SiC addition enhances Jc(H) more significantly through intrinsic and extrinsic pinning.

Optimal doping levels improve critical current density and upper critical field.

Abstract

The enhancement of the critical current density (Jc(H)) of carbon and nano-SiC doped MgB2 is presented and compared. The upper critical field (Hc2) being determined from resistivity under magnetic field experiments is though improved for both C substitution and nano-SiC addition the same is more pronounced for the former. In MgB2-xCx carbon is substituted for boron that induces disorder in the boron network and acts as internal pinning centres. The optimal Jc(H) values are obtained for x = 0.1 sample . In case of nano-SiC doped in MgB2, the Jc(H) improves more profoundly and two simultaneous mechanisms seems responsible to this enhancement. Highly reactive nano-SiC releases free carbon atom, which gets easily incorporated into the MgB2 lattice to act as intrinsic pinning centres. Further enhancement is observed for higher nano-SiC concentrations, where the un-reacted components serve as additional extrinsic pinning centres.