Effects of Sintering Condition on the Trapped Magnetic Field Properties for MgB2 Bulks Fabricated by in-situ Capsule Method

We have studied the trapped field properties of MgB2 bulks which were fabricated by the in-situ capsule method under various sintering temperatures of 700-900 ̊C for 1-24 h. The trapped field, BT (T), was 1.8-1.9 T for all the bulks approximately at 16 K. The BT (T) values on the bulks sintered at 900 ̊C for 6 h and at 800 ̊C for 24 h were slightly lower than those of other bulks because of the decrease of critical current density, Jc, which originates from both the lower connectivity, K, and the promotion of the grain growth. The high temperature and/or the long periods sintering decrease the BT (T) value. From the obtained results, the sintering at 700-800 ̊C for 1-6 h is the optimum condition to fabricate MgB2 bulks by the capsule method.