Effects of the Size of the Doped SiC Nanoparticles on the Critical Current Density of the Ti-Sheathed MgB $_{2}$ Superconducting Wires

The effects of the grain size of the doped SiC nanoparticles on the critical current density (J_c) of the Ti-sheathed MgB₂ superconducting wires were studied. The concentration of the SiC dopant was 10% and the sizes of the SiC particles were 20 nm, 45 nm, and 123 nm. Contrary to the J_c results reported on the SiC-doped Fe-sheathed MgB₂ wires, we found that the J_c for the Ti-sheathed MgB₂ wires decreased with the size of the SiC particles. We also found that the J_c is greater than that of the undoped MgB₂ wires only for the wires with 123 nm SiC size. This unusual dependence of J_c on the size of the SiC dopant is discussed in association with the results from the magnetization, electrical resistivity, x-ray diffraction, and transmission electron microscopy measurements.