Improvement in the Performance of Bulk MgB₂ Material through Optimization of Sintering Process

Enhancement of the critical current density (J_c) in MgB₂ bulk material is very important for engineering applications. It has been found that the optimization of the sintering temperature leads to high J_c values in bulk MgB₂ material. In our recent work, the highest trapped field value was recorded in the sample sintered at 775^oC. The present investigation has focused on methods to improve further J_c values of the disk-shape bulk MgB₂ superconductors by optimizing sintering conditions. MgB₂ samples were subjected to a solid state reaction at 775, 780, 785, 795, 800 and 805^oC for 3 h in pure Ar atmosphere. XRD analysis showed that all the samples were single phase MgB₂. The magnetization measurements confirmed a sharp superconducting transition with onset T_c at around 38.7 K. Atomic force microscopy observation indicated that the number of nano meter size grains is more in samples processed 3 h at 805^oC has compared to the samples sintered at 775^oC. As a result, the highest J_c value of 245 kA/cm² at 20 K was obtained for the sample sintered at 805^oC for 3 h.