The microstructures of MgB2/Fe tapes fabricated by using an in situ powder-in-tube method, with MgH2 as a precursor powder, were studied by means of X-ray diffraction and analytical transmission electron microscopy combined with a focused ion beam microsampling technique. The overall microstructures of the tapes were characterized as being densely crystallized MgB2 areas with 10 to 200nm grain size, uncrystallized areas containing mainly MgO and amorphous phases enriched with B, and a number of holes and cracks. The crystallized MgB2 areas increased upon doping with SiC nanoparticles. The Si and C atoms decomposed from SiC nanoparticles during heat treatment exhibited differing spatial distributions: the Si atoms were inhomogeneously distributed, forming silicides such as Mg2Si with a grain size of 5 to 20nm. The C atoms tended to be uniformly distributed within the MgB2 matrix. A significant difference in the distribution of O atoms between the SiC-doped and non-doped specimens was observed. The process of formation of these microstructures and its relationships to the critical current density under magnetic fields were considered.

Microstructures of MgB2/Fe Tapes Fabricated by an in situ Powder-in-Tube Method using MgH2 as a Precursor Powder. S.Hata, T.Yoshidome, H.Sosiati, Y.Tomokiyo, N.Kuwano, A.Matsumoto, H.Kitaguchi, H.Kumakura: Superconductor Science and Technology, 2006, 19, 161-8