Effect of Dy₂O₃ doping on phase formation and properties of MgB₂ wires made by the modified internal magnesium diffusion process

A series of single-core MgB₂ wires was produced by the modified internal magnesium diffusion process, starting with a Mg tube filled with carbon predoped boron powder, which resulted in an extractable MgB₂ core allowing thorough investigation of superconducting properties. Carbon contained in the boron powder enhances critical current density ( J _c), however, it also reduces the reactivity of boron and thus acts as a MgB₂ growth inhibitor. In order to compensate this negative effect, Dy₂O₃ nanopowder was added into boron powder and the composites were subjected to heat-treatment at increased temperature for a longer time. By this approach, the reactivity of carbon predoped boron was substantially improved, yielding wires with an increased amount of MgB₂ of high phase purity with enhanced J _c. (paper)