Effects of carbon substitution via ball-milling in MgB 2

Abstract

In this study, we have synthesized the C-doped MgB 2 samples by solid-state reaction after mixing Mg powder with the attrition-milled B and C powders. The C added powders were mixed according to the nominal atomic ratio of Mg(B 1− x C x ) 2 with x = 0, 0.005, 0.015, 0.025, and 0.05. The analysis of X-ray diffraction showed that the (1 1 0) peaks, which correspond to the lattice parameter a, were shifted to a higher angle as the increasing of carbon contents. These results indicated that the B substitution for C became more dominant at higher doping level of C. The sample having the composition of Mg(B 0.975C 0.025) 2 gave the best critical current density ( Jc) of ≈5000 A cm −2 at 8 T and 5 K, as compared to the ≈1200 A cm −2 for the undoped sample.