Tube filling technique influence on superconductivity in MgB2-based   conductors prepared using laboratory made boron
  Here we report a systematic study of superconductive properties of mono-filamentary MgB2-based wires, manufactured with different filling technique. A detailed comparison of the influence of filling technique and final heat treatment on superconducting properties has been given. Boron used was synthesized in laboratory following magnesiothermic reduction of boron oxide, purified thanks to several acid leaching and heat treated at high temperature, to enhance crystalline degree. Critical current density and critical temperature have been investigated at different synthesis/sintering temperature in order to evaluate their dependence to applied final heat treatment. Critical current density has been evaluated on short wire pieces by magnetic measurement in a MPMS 5.5T Quantum Design SQUID, while critical temperature has been measured with a four probe system, by the drop of resistivity during the cooling of the sample in a liquid helium dewar. 
Gianmarco Bovone, Davide Nardelli, Davide Matera, Maurizio Vignolo
cond-mat.supr-con