Effect of Carbon and SiC Doping on Microstructures of MgB2 Bulks and Wires by a Two-Step Reaction Method

Abstract

Carbon and SiC doped MgB 2 bulks and wires were fabricated by a two-step reaction method. The MgB 4 samples were sintered at 900 °C for 2 h in closed argon atmosphere, and then an appropriate amount of Mg powder was mixed with the ground MgB 4 powder to get MgB 2 green compacts, which were sintered at 750 °C for 2 h to get bulk samples or at 680 °C for 2 h to get wire samples in closed argon atmosphere. Carbon or SiC doped MgB 2 bulk samples were also prepared by conventional solid state sintering for comparison. The phase evolution and the microstructure of MgB 2 samples were characterized by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). The SEM results indicate that the compactedness and the dopant distribution homogeneity of MgB 2 samples prepared by the two-step reaction method are improved obviously. The carbon doping can more effectively introduce the dopants into MgB 2 crystalline lattice and grain boundaries compared with SiC doping.