Improvement of the current carrying capability ofex situMgB2wires by normal particle additions

A wide variety of powders, including Nb, Ti, Zr, Hf and W, metal oxides like Nb 2 O 5 , Ti 2 O 5 , V 2 O 5 and other compounds like SiC, SrCO 3 and boron nitride, have all been used at the 10 wt% level as additions into commercial MgB 2 powder for the fabrication of single-core, ex situ wires using groove and two-axial rolling deformation and final heat treatment at 950 °C /0.5 h in Ar. Transport current measurements have shown that metal particle addition leads to an especially significant improvement in current carrying capacity. The presence of normal particles influences both the resistivity and also the thermal conductivity of the MgB 2 core, and the improved internal stability may be responsible for the increased critical current values. This observation may be very important for future development of practical MgB 2 composite superconducting wires.