Effects of the sintering temperature and doping of C60 and SiC on the critical properties of MgB2

We fabricated MgB2 using the powder-in-tube (PIT) method with the in situ route and evaluated the effects of the sintering temperature and doping of fullerene (C60) and SiC on the critical properties. It was found that a sintering temperature in the range of 650-750 deg C was more effective in maintaining good Jc vs. H behavior than a sintering temperature of 900 deg C, which is probably due to the resultant poorer crystallinity and smaller grain size, which provide more grain boundary that act as flux pinning center. In addition, we selected C60 as a new dopant, because it has a low decomposition temperature (about 280 deg C), and compared the doping effect of C60 to that of SiC. It was observed that the wire doped with 10 wt.% of C60 had a Jc value of as high as 1.60 X 104 A/cm2 at 5 T and 5 K, which was comparable to that of the Jc of 5 wt.% SiC doped wire (1.64 X 104 A/cm2). On the other hand, the C60 doped wire did not degrade the Tc distinguishably with increasing C60 content to 10 wt.%.