Effects of doping with nanoscale Co3O4 particles on the superconducting properties of powder-in-tube processed MgB2 tapes

Nanoscale Co3O4 particles were doped into MgB2 tapes with the aim of developing superconducting wires with high-current-carrying capacity. Fe-sheathed MgB2 tapes with a mono-core were prepared using the in situ powder-in-tube (PIT) process with the addition of 0.2–1.0 mol% Co3O4. The critical temperature decreased monotonically with an increasing amount of doped Co3O4 particles for all heat-treatment temperatures from 600 to 900 °C. However, the transport critical current density (Jc) at 4.2 K varied with the heat-treatment temperatures. The Jc values in magnetic fields ranging from 7 to 12 T decreased monotonically with increasing Co3O4 doping level for a heat-treatment temperature of 600 °C. In contrast, some improvements on the Jc values of the Co3O4 doped tapes were observed in the magnetic fields below 10 T for 700 and 800 °C. Furthermore, Jc values in all the fields measured increased as the Co3O4 doping level increase from 0 to 1 mol% for 900 °C. This heat-treatment temperature dependence of the Jc values could be explained in terms of the heat-treatment temperature dependence of the irreversibility field with Co3O4 doping.