Influence of hydrogen-containing argon gas on the structural parameters and superconducting properties of malic acid-doped MgB2 wires

We have studied the influence of hydrogen-containing argon gas on the structural and superconducting properties of MgB2 wires. Lattice parameters were independent of the concentration level of hydrogen in argon, while the fraction of the secondary phase, MgO, was sensitive. The MgO particles observed by scanning transmission electron microscopy were 30–50 nm in size, which is considerably larger than the appropriate size range of flux pinning centers. The sintering atmosphere conditions are a crucial issue for MgB2 wires.

► Influence of hydrogen containing argon gas on the structural parameters and superconducting properties of malic acid-doped MgB2 wires.
► Malic acid-doped wires were sintered in hydrogen containing argon gas.
► The fraction of the secondary phase, MgO, was proportional to the hydrogen content. This led to a decrease in transport critical current density for the MgB2 wires.
► The MgO particles were 30–50 nm in size and could not serve as flux pinning centers.