Investigation of MgB2/Fe wires with different diameters

MgB2/Fe wires with different diameter were fabricated by using the in situ powder-in-tube method. Samples were sintered at 750 degrees C for 1 h in a flow of high purity argon gas. The phase composition is identical for all the wires. The J(c)(B) values of these wires generally increase with decreasing diameter from 1.60 to 1.40 to 1.29 mm, but decrease significantly to the lowest value at a diameter of 1.20 mm. It is revealed that the optimum diameter of 1.29 mm, at which the MgB2/Fe wire possessed the optimal J(c)(B) property, was determined by the variations of the green density of the Mg/2B mixture in the core and the relative thickness of the Fe sheath during the mechanical deformation process.