Development of Ti-sheathed MgB₂ wires with high critical current density

Working towards developing lightweight superconducting magnets for future space and other applications, we have successfully fabricated mono-core Ti-sheathed MgB₂ wires by the powder-in-tube method. The wires were characterized by magnetization, electrical resistivity, x-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry measurements. The results indicate that the Ti sheath does not react with the magnesium and boron, and the present wire rolling process can produce MgB₂ wires with a superconducting volume fraction of at least 64% in the core. Using the Bean model, it was found that at 5 K, the magnetic critical current densities, J_c, measured in magnetic fields of 0, 5, and 8T are about 4.2 × 10⁵, 3.6 × 10⁴, and 1.4 × 10 ⁴Acm^-2, respectively. At 20K and 0T, the magnetic J _c is about 2.4 × 10⁵Acm^-2. These results show that at zero and low fields, the values of the magnetic J_c for Ti-sheathed MgB₂ wires are comparable with the best results available for the Fe-sheathed MgB₂ wires. At high fields, however, the J _c for Ti-sheathed MgB₂ wires appears higher than that for the Fe-sheathed MgB₂ wires.