Superconducting properties and magneto-optical imaging of Ba0.6K0.4Fe2As2 PIT wires with Ag addition
We have fabricated (Ba,K)Fe2As2 superconducting wires through an ex?situ powder-in-tube method. Silver was used as a chemical addition to improve the performance of these superconducting wires. The transport critical current densities (Jc) have reached 1.3???104?A?cm?2 and 1.0???104?A?cm?2 at 4.2?K under self-field in the wires with and without Ag addition. We used a magneto-optical (MO) imaging technique to investigate the properties of grain boundaries in the (Ba,K)Fe2As2 superconducting wire with Ag addition. MO images show the weak links in the Fe-based superconducting wires for the first time. An intragranular Jc of 6.0???104?A?cm?2 at 20?K is obtained from the MO image, which is consistent with the estimation from M?H measurement.