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

摘要

The effects of the grain size of the doped SiC nanoparticles on the critical current density $(J_{rm c})$ of the Ti-sheathed $hbox{MgB}_{2}$ 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 $J_{rm c}$ results reported on the SiC-doped Fe-sheathed $hbox{MgB}_{2}$ wires, we found that the $J_{rm c}$ for the Ti-sheathed $hbox{MgB}_{2}$ wires decreased with the size of the SiC particles. We also found that the $J_{rm c}$ is greater than that of the undoped $hbox{MgB}_{2}$ wires only for the wires with 123 nm SiC size. This unusual dependence of $J_{rm c}$ 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.