Fabrication of Superconducting MgB_2-Based Nanocomposites with Magnetic Inclusions by Spark Plasma Sintering

摘要

We present the fabrication, structural, and transport properties of MgB_2-based ceramic composites with magnetic nanospheres fabricated by spark plasma sintering. The nanospheres are either carbon-encapsulated iron or iron oxide. The former nanospheres have been prepared by laser pyrolysis whereas the iron oxide was obtained by the pyrolysis of the polysiloxane-based copolymers embedded into MgB_2 matrix during the sintering process. The structural data show the shrinkage of the α-axis lattice constant as a result of the partial carbon substitution for boron. However, the transport data suggest that carbon diffusion is limited to the outer layer of the MgB_2 grains in both cases.