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

Abstract We have investigated the influence of B 2 H 6 gas mixture flow rate and deposition time on superconducting properties of MgB 2 tapes. The MgB 2 tapes are fabricated by growing the MgB 2 films on Hastelloy tapes at a temperature of 520 °C by using hybrid physical–chemical vapor deposition (HPCVD) technique. The MgB 2 tapes exhibit transition temperature ( T c ) 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 MgB 2 tapes are polycrystalline in nature. MgB 2 grains of various orientations are observed in the microstructures of the tapes taken by scanning electron microscopy. We obtained much higher J c values over the wide field range for MgB 2 tapes grown on Hastelloy than the previously reported data on other metallic substrates, such as Cu, SS, and Nb. The critical current density ( J c ) of about 10 5  A/cm 2 at 5 K under 3 T is obtained for the MgB 2 tape of thickness 2 μm. These results suggest that the thick MgB 2 /Hastelloy tapes with high J c values deposited under controlled growth conditions of HPCVD could be useful in high-field applications.