Improvement of Current-Carrying Capacity and In Situ Control of the Superconducting Fraction of MgB2-MgO Composites

Abstract

Superconducting magnesium diboride-magnesium oxide (MgB 2-MgO) composite attracts our attention due to its relatively high superconducting transition temperature close to the one of a pure MgB 2 bulk and metallic transport behavior with low resistivity in the normal state even at a high fraction of insulating MgO. In this paper, we report that the current-carrying capacities of MgB 2-MgO composites were enhanced by improving the replacement reaction process, and the superconducting MgB 2 fraction can be in situ controlled by using magnesium (Mg), boron trioxide (B 2O3), and boron (B) as the raw materials. The composites with mass fractions of superconducting MgB 2 from 27 to 80 % show that the zero-resistance transition temperatures are above 36.7 K, and the self-field critical current densities are from 0.2 ×106 to 4 ×106 A/cm 2 at 10 K. The high JcS of the superconducting composites under the applied fields prove that there is no appreciable difference between a perfect MgB 2 sample and one with MgO doping, but the critical current density and flux pinning are improved. These results are meaningful for studying further the flux-pinning mechanism in MgB 2.