Influence of the Preparation Process on Microstructure, Critical Current Density and Tc of MgB2 Powder-In-Tube Wires

摘要

MgB2 wires and tapes suffer from a limitation of the transport currentdensities, especially at low field, due to an unsufficient thermalstabilization caused by hot spots from a non-homogeneous microstructure, thepresence of secondary phases and voids. For the preparation of MgB2 wires andtapes two different precursor routes, using MgB2 (ex-situ process) or Mg + B(in-situ process) are applied. The in-situ approach allows variation of manyparameters in the wire preparation and the improvement of this approach is thecentral topic of this paper. We present an improved in-situ approach, thecharacterization of the filament microstructure, effects from stoichiometry andthe corresponding superconducting properties. The transport current capabilityof such in-situ wires could be improved to the level of the reference ex-situwires.