Superconductive property and structure of MgB2 wires manufactured by external diffusion method

MgB2 wires have been prepared by diffusion process using pure Mg metal tube. Amorphous B powder mixed with 5 mol% SiC nano-sized powder addition was encased in a Mg tube, and then the tube was inserted into a pure iron tube to form the Fe/Mg/B(powder) composite wires. The composite was drawn into around wires of 1.0 ~ 0.8 mm in diameter without intermediate annealing. The composite wires were heat treated at 630 °C for 5 h in Ar gas atmosphere. Some of the specimens were hot-pressed under 10 MPa during heat treatment. The MgB2 core was synthesized through the diffusion reaction between outside Mg metal tube and inside B powder with SiC addition. The MgB2 core forms denser structure without voids and cracks in comparison with conventional in-situ PIT processed MgB2 wires. The Ic values at 4.2 K for the MgB2 wire of 1.0 mm and 0.8 mm in diameter reaches to 134 A and 187 A at 5 T ,which corresponds to the Jc of 2230 A/mm2 and 3740 A/mm2, respectively. The Ic of the hot-pressed wire is 164 A at 5 T.