Effects of Silver Addition on Critical Current Densities and Mechanical Properties in Bulk MgB2

The present study focuses on the effects of Ag addition on the critical current density (Jc) and the mechanical performance of disk‐shaped MgB2 bulk superconductors. MgB2 samples with varying Ag contents of 0, 2, 4, 6, 8, and 10 wt% were sintered at 775 °C for 3 h in Ar atmosphere. The Jc values were improved with Ag addition, in that the sample with 4 wt% Ag showed the highest Jc value of 295 kA cm−2 at 20 K and self‐field. The respective Jc values of the same sample were 430, 360, and 238 kA cm−2 in self‐field, 0.5 T, and 1 T at 7 K. These values are the highest so far reported in bulk MgB2 materials. Scanning electron microscopy showed that silver and silver oxide particles are embedded in the voids. As a result, the mechanical performance at room temperature was improved with Ag addition. We also confirmed the presence of nanometer‐sized AgMg3 particles, which may be responsible for high flux pinning and improved mechanical performances.