Influence of the milling energy transferred to the precursor powder on the microstructure and the superconducting properties of MgB₂wires

Abstract

A systematic study of the influence of the milling energy of the precursor powder on the microstructure and the superconducting properties of MgB2 bulk samples and wires, and, in addition, the deformation behavior of the wires is presented. An explicit approximate formula for the energy transferred to the powder sample during milling and its dependence on the parameters of the milling process is developed and used for the data analysis. For higher milling energies the amount of the reacted MgB2-phase shows a strong increase. The transport critical current density of wires can be enhanced by using precursor powder milled with higher energy. Because the deformation properties are degraded to some extent, one has to find a compromise of the preparation parameters between current density and deformation behavior.