1 Department of Energy Conversion and Storage, Technical University of Denmark2 Electrofunctional materials, Department of Energy Conversion and Storage, Technical University of Denmark3 Department of Physics, Technical University of Denmark4 Neutrons and X-rays for Materials Physics, Department of Physics, Technical University of Denmark5 Institute of Chemical Technology6 Deutsches Elektronen-Synchrotron
MgB2 bulk and wire samples were prepared using cheap, low grade amorphous boron powders. Based on chemical analysis performed on the starting reagents, three nominal stoichiometries were studied. It was found that the structural and superconducting properties of the bulk samples were not affected by the composition, but that residual Mg was left in the wires for the nominal MgB2 composition. In contrast, slightly Mg-deficient compositions were free from residual Mg and exhibited higher critical current densities. The MgB2 phase formation kinetics was not influenced by the variations in the nominal powder composition.
Journal of Superconductivity and Novel Magnetism, 2014, Vol 27, Issue 2, p. 497-504