Microstructure and superconducting properties of MgB2

A. SERQUIS

Buenos Aires, Argentina

Workshop; Seventh J. J. Giambiagi Winter School; 2005

Universidad de Buenos Aires

The strong potential for commercial applications of MgB2 is due to a unique combination of characteristics, such as the highest transition temperature (Tc~39 K) for a binary compound, the chemical simplicity, the lightweight and the low cost of raw materials. In addition, the absence of weak-link behavior at grain boundaries in polycrystalline samples allows the use of simple powder in tube (PIT) methods to fabricate wires and tapes. Several groups have achieved a substantial improvement of the transport properties in a magnetic field that is significantly larger than the low irreversibility field (Hirr) of the clean basic compound, making MgB2 a candidate to replace NbTi or Nb3Sn in magnets. The introduction of more pinning centers and the connectivity enhancement of grains are both necessary to increase Hirr and the critical current density (Jc) at intermediate temperatures, which can be reached by both liquid He as well as commercial cryocoolers. These features can be achieved in many ways, i.e. by doping or nanoparticle addition, and effective heat treatments such as hot isostatic pressing. Another interesting feature is the presence of two superconducting gaps, which allow tuning different upper critical fields (Hc2) by controlling different defect sublattices relative to orthogonal hybrid bands. In this talk, a review of the main characteristics of the recently discovered MgB2 superconductor will be presented and a correlation between the microstructure and superconducting properties will be discussed.