Electric and Magnetic Characterization of Bulk Ag-added MgB2
Résumé
In earlier studies it was found that bulk, sintered MgB2 samples contained numerous voids which hinder the current flow. Therefore, a series of bulk MgB2 superconductors with Ag contents of 0 – 10 wt% was prepared in order to improve the critical current densities and the mechanical performance. Several samples were fabricated using a solid state reaction in pure Ar atmosphere at the optimal reaction temperature of 775 °C. Thorough microstructural observations obtained from scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicate that metallic Ag particles are embedded in the void regions. Furthermore, nanometer-sized AgMg3 particles are also present within the MgB2 matrix, leading to improved flux pinning. Small samples cut from the bulk were characterized by electric transport measurements [R(T,B) and I/V characteristics] in magnetic fields up to 8 T and by magnetization loops measured using a SQUID magnetometer.