earticle

영어

Since the MgB2 superconductor is simply composed of two constituents of Mg and B, its performance can be monitored easily with the change of one ingredient compared to the other. With the powder size of B less than 100 nm, two different sizes of Mg powders are used to investigate the reaction temperature dependence of MgB2 bulk samples. In the range of 630-700oC for the duration of 30 min., the un-reacted Mg is seen only at 630oC with Mg powder size of <5 μm, whereas Mg traces are detected at all the temperature range with Mg powder size of <45 μm. The reaction temperature dependence of MgB2 superconducting transition temperature, Tc, shows little difference whether Mg powder size is large or small in this range except for the 630oC. It is worthy of notice that the critical current densities of MgB2 show higher performance with the small size of Mg compared to the large one at all field ranges. With the Mg powder size of <45 μm, flux pinning is enhanced with decreasing the reaction temperature, whereas flux pinning properties is quite similar in the Mg powder size of <5 μm except for the 630oC, where Mg is left behind after the reaction.