Enhanced J_c of B-rich and SiC doped MgB_2 tapes fabricated by a modified in-situ PIT method with two stage heat treatment

摘要

B-rich and SiC doped MgB_2 tapes were fabricated by a modified in-situ PIT method with two stage heat treatment. B composition ratio and an amount of SiC doping were systematically changed. The effect of pre-heating and final heating conditions on J_c-B properties was also studied. Mean grain size of MgB_(2.8) specimens reduced to about 100 nm by increasing SiC doping 5.7%. In low fields J_c slightly increased for a little SiC doped specimens. On the other hand, in high fields, J_c obviously increased with increasing SiC doping. Maximum J_c reached 1.8× 10~3 A/cm~2 at 3 T, 20 K for MgB_(2.8) specimen doped SiC 5.7 mol%. B_(irr) also increased with increasing SiC doping. J_c systematically increased with the decrease of temperature of pre-heat treatment. In contrast J_c systematically increased with the increase of temperature of final heat treatment. Best J_c of 8.6×10~4A/cm~2 at 20 K, 0 T was achieved for specimen with 700 °C for 5 hours + 800 °C for 1 hour heating. B_(irr) tended to increase with the increase of J_c.