Effects of Metal (Ag, Sn and Zn) Nanoparticles Inserted into MgB₂ Grain Boundaries on Transport and Superconducting Properties

抄録

MgB₂ grains were coated with metal nanoparticles (Ag, Zn and Sn) using the barrel sputtering technique, and transport and superconducting properties were evaluated. Almost all MgB₂ grains were uniformly coated with metal nanoparticles with average diameters of less than 20 nm. The electrical resistivity of the coated MgB₂ decreased as the amount of metal coating increased. The critical current densities of almost all coated MgB₂ were enhanced compared to those of bare MgB₂. These results explained the improvement of intergranular connectivity between MgB₂ grains by the insertion of metal nanoparticle in grain boundaries. After annealing at 473 K, only MgB₂ coated with Sn nanoparticles showed a decrease in electrical resistivity and the enhancement of the critical current density. These results can be understood by the effect of improvement of intergranular connectivity between MgB₂ grains by annealing.