Effect of sintering temperature on structural defects and superconducting properties in MgB2 + C4H6O5

We report a systematic study on the effect of sintering temperature on the lattice parameters, amount of carbon (C) substitution, microstructure, critical temperature (Tc), critical current density (Jc), upper critical field (Hc2) and irreversibility field (Hirr) of 10 wt% Malic acid (C4H6O5) doped MgB2 superconductors. All the samples were heat treated at temperatures ranging from 600 to 900ºC. With increasing the sintering temperature both the a-axis lattice parameter and Tc are decreased compared to un-doped samples, indicating that the C released from C4H6O5 substituted into Boron (B) position resulting in the enhancement of Jc, Hc2 and Hirr.