The effect of carbon doping on the upper critical field (Hc2) and resistivity of MgB2 by using sucrose (C12H22O11) as the carbon source

In this work, sucrose was doped into MgB2 samples to act as a carbon source. The sintering temperature varied from 850 to 1050 deg. C. The effects of sucrose doping and sintering temperature on the lattice parameters, microstrain, critical temperature (Tc), resistivity, and upper critical field (Hc2) have been investigated in detail. It has been found that sucrose doping results in a small depression in Tc and high resistivity, while the Hc2 performance is improved. The best performance was shown in the sucrose-doped sample sintered at 850 deg. C. The reason for the enhancement of Hc2 is likely to be disorder caused by C substitution for B and/or diffusion of C atoms in the MgB2 lattice as interstitial atoms.