Improvement of the critical current properties of in situ powder-in-tube-processed MgB2 tapes by hot pressing

We applied hot pressing to in situ powder-in-tube-processed (PIT-processed) MgB2 tapes. We enhanced the superconducting properties by adding nanometer-sized SiC powder and ethyltoluene (C9H12) to the mixed powder. Hot pressing was performed at 100 MPa and 630 0C in an Ar gas atmosphere for 2-10 h. Hot pressing reduced the cross-sectional area of the MgB2 tapes from ∼ 0.55 mm2 for conventionally heat-treated tapes to ∼ 0.44 mm2. This increased the MgB2 core density from 50% to 70%. Undoped MgB2 tapes hot pressed for 5 h exhibited a transport Jc of 90 A mm-2 at 4.2 K and 10 T, which is about three times greater than that for a tape heat treated without hot pressing. The value of Jc for codoped tape hot pressed for 5 h was 450 A mm-2 at 10 T, which is larger than that for codoped tape heat treated without hot pressing (280 A mm-2). These results clearly demonstrate that hot pressing is effective in increasing the MgB2 core density, and hence in enhancing the Jc values of PIT-processed MgB2 tapes.