Improvement of in-situ Fe/MgB2 monofilamentary wires by internal Mg-coating process

Abstract

In the present work, we have studied on the use of internally Mg-coated and uncoated iron tubes in processing of in-situ mono filamentary Fe/MgB2 wires by means of transport measurements and structural analysis methods. For coated wires, the starting Fe tube is internally coated by magnesium before PIT process is applied and these wires with 0.81 mm in diameter are heat treated at different annealing temperatures and times. The main idea behind this work is to investigate the possible role of Mg coating on inhibition of Fe2B phase formation and its contribution to granular structure of MgB2 core. The transport and superconducting properties in the presence of external magnetic field are well improved for Mg-coated wire samples in comparison to the uncoated wire samples. The structural and surface analyses of Mg-coated wires reveal that the Fe2B formation still exists at the interface region. The results are interpreted in terms of effects of excess magnesium, internal Mg vapor pressure, homogeinity of Mg coating process, and heat treatment conditions. The highest engineering critical current density Jce(4.2 K) is obtained as greater than 5.4 × 104 A/cm2 at μ0H = 4 T among the coated samples.