Improvement of Critical Current Density and Upper Critical Field in MgB2 using Carbohydrate

TL;DR

This study demonstrates that doping MgB2 with carbohydrate (malic acid) significantly improves its critical current density and upper critical field by inducing carbon substitution, which enhances impurity scattering and superconducting properties.

Contribution

It provides new insights into using carbohydrate doping to enhance MgB2 superconductor performance, showing a substantial increase in critical current density and upper critical field.

Findings

Critical current density increased by a factor of 21 at 5 K and 8 T.

Lattice parameter a decreases indicating carbon substitution.

Resistivity increased, correlating with enhanced upper critical field.

Abstract

We evaluated the doping effects of carbohydrate (malic acid, C4H6O5), from 0wt% to 30wt% of total MgB2, on the phase, lattice parameters, critical temperature, resistivity, and upper critical field of MgB2 superconductor. The lattice parameters calculated show a large decrease in the a-axis for MgB2 + C4H6O5 samples, but no change in the c-axis. This is an indication of the carbon substitution into boron coming from C4H6O5, resulting in enhancement of resistivity, critical current density, and upper critical field. Specifically, the critical current density value of 25000 Acm2 at 5 K and 8 T for the MgB2 + 30wt% C4H6O5 sample is higher than that of the un-doped MgB2 by a factor of 21. In addition, resistivity value for all the MgB2 + C4H6O5 samples ranged from 80 to 90 microohm centimeter at 40 K, which is higher than for un-doped MgB2. The increased resistivity indicates increased impurity scattering due to carbon, resulting in enhanced upper critical field.