Improvement of the critical current properties ofin situpowder-in-tube-processed MgB2tapes by hot pressing

We applied hot pressing to in situ powder-in-tube-processed (PIT-processed) MgB 2 tapes. We enhanced the superconducting properties by adding nanometer-sized SiC powder and ethyltoluene (C 9 H 12 ) to the mixed powder. Hot pressing was performed at 100 MPa and 630 °C in an Ar gas atmosphere for 2–10 h. Hot pressing reduced the cross-sectional area of the MgB 2 tapes from ∼ 0.55 mm 2 for conventionally heat-treated tapes to ∼ 0.44 mm 2 . This increased the MgB 2 core density from 50% to 70%. Undoped MgB 2 tapes hot pressed for 5 h exhibited a transport J c 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 J c 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 MgB 2 core density, and hence in enhancing the J c values of PIT-processed MgB 2 tapes.