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

Abstract

The present study focuses on the effects of Ag addition on the critical current density ( J c ) and the mechanical performance of disk‐shaped MgB 2 bulk superconductors. MgB 2 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 J c values were improved with Ag addition, in that the sample with 4 wt% Ag showed the highest J c value of 295 kA cm −2 at 20 K and self‐field. The respective J c 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 MgB 2 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 AgMg 3 particles, which may be responsible for high flux pinning and improved mechanical performances.