Effects of B2H6 flow rate and deposition time on superconducting properties of MgB2/Hastelloy tapes

We have investigated the influence of B2H6 gas mixture flow rate and deposition time on superconducting properties of MgB2 tapes. The MgB2 tapes are fabricated by growing the MgB2 films on Hastelloy tapes at a temperature of 520 °C by using hybrid physical–chemical vapor deposition (HPCVD) technique. The MgB2 tapes exhibit transition temperature (Tc) of around 39 K and is found to be unaffected by the gas flow rate but shows a slight dependence on the deposition time. X-ray diffraction analysis revealed that the MgB2 tapes are polycrystalline in nature. MgB2 grains of various orientations are observed in the microstructures of the tapes taken by scanning electron microscopy. We obtained much higher Jc values over the wide field range for MgB2 tapes grown on Hastelloy than the previously reported data on other metallic substrates, such as Cu, SS, and Nb. The critical current density (Jc) of about 105 A/cm2 at 5 K under 3 T is obtained for the MgB2 tape of thickness 2 μm. These results suggest that the thick MgB2/Hastelloy tapes with high Jc values deposited under controlled growth conditions of HPCVD could be useful in high-field applications.

► MgB2 films were fabricated on polycrystalline Hastelloy tapes.
► Effects of B2H6 gas flow rate and deposition time on MgB2 tapes were studied.
► Tc of the tapes is found unaffected by flow rate but depends on deposition time.
► High Jc values obtained for MgB2/Hastelloy tapes.
► Hastelloy is a promising metallic substrate for fabrication of MgB2 conductors.