Synthesis of the superconducting MgB2 film on the W-wire by co-evaporation method

We have synthesized the MgB2/W composite fiber by depositing MgB2 film on the W-wire with co-evaporation system. Boron was sputtered with the RF-magnetron sputter and magnesium was thermally evaporated simultaneously during deposition. For the uniformity of the deposited layer and the precise stoichiometric compound formation of the MgB2 film layer, specimen holding unit was rotated at a fixed rate and the sputtered rate of B and evaporated rate of Mg were controlled separately. After post-annealing of the MgB2/W-wire at 600 degrees C, we could obtain 100-800 nm MgB2 layers with uniform composition. Occasionally un-reacted Mg or second phases such as MgWO4 were observed depending on the experimental conditions. The phase evolution and the microstructure of the deposited MgB2 film were investigated with XRD, SEM, and EDS. The superconducting transition temperatures (T,) and the average critical current density have been measured around similar to 33.5 K and 3.7 x 10(3) A/cm(2), respectively using the physical property measurement system (PPMS 9T, Quantum Design). (c) 2010 Elsevier B.V. All rights reserved.