We fabricated MgB
2 tapes and wires by a powder-in-tube (PIT) method, using MgB
2 powder and several sheath materials such as Cu, Cu-Ni, Ni, pure Fe, carbon steel (Fe-C), and stainless steel.
Jc of the as-cold rolled (un-sintered) tape significantly increased with the increase of total cross-sectional area reduction by the cold working. Hard sheath materials such as Fe-C and stainless steel are effective to enhance the packing density of MgB
2 core and, therefore, to increase
Jc values. Non heat treated MgB
2 tapes with Fe-C and stainless steel sheaths showed extrapolated
Jc values of-3.0-4.5×10
9A/m
2 at 4.2K and zero field. Heat treatment after the cold rolling is effective to enhance
Jc values. An order of magnitude higher
Jc values were obtained for Fe, Fe-C, and stainless steel sheathed tapes after the heat treatment. Extrapolated
Jc values well above 10
10A/m
2 at 4.2K and a zero magnetic field were obtained for stainless steel and Fe-C sheathed MgB
2 tapes.
Jc values of PIT-processed MgB
2 tapes are less sensitive to strain than those of PIT-processed Bi-based oxide tapes. It is reported that the addition of soft metal powder such as In or Sn to the MgB
2 powder is effective to enhance
Jc values. We made -10m-long tapes with Ni sheaths, and fabricated small solenoid coil with this tape without sintering. The
Ic of the coil was about 80% of the
Ic of the short tape, indicating that the homogeneity of
Ic in the 10m tape is fairly good. The coil generated 1.3kGauss at 4.2K.
抄録全体を表示