Effects of ZrH2 doping and sintering temperature on the critical current density of MgB2 wires

ZrH2-doped MgB2 wires, with the composition of Mg:ZrH2:B = (1 − x):x:2 (x = 0%, 5%, 8%, 10%, 12%, 15%), were fabricated through the in situ powder-in-tube method by using low carbon steel tubes as sheath materials. Samples were sintered at 700 °C, 750 °C, 800 °C and 900 °C for 2 h respectively in a flow of high purity argon. It is found that the amount of ZrB2 increases with the doping ratio, and the content of Fe2B increases with the sintering temperature. Critical current density (Jc) of all the doped samples decreases with the increase of sintering temperature, but the optimum doping ratio goes up correspondingly. Among all the doped samples, the samples of x = 5% and x = 8% exhibit better Jc properties at the sintering temperature of 700 °C, but the samples of x = 10%, 12% and 15% present higher Jc values when sintered at 900 °C.