Effects of MgO on the electronic and superconducting properties in succinic acid (C4H6O4) doped MgB2 bulks

In this paper, we report the doping effects of succinic acid, C4H6O4 (from 0 to 30 wt%) on the lattice parameter, critical temperature (T-c), critical current density (J(c)), upper critical field (H-c2), and irreversibility field (H-irr) in MgB2 superconductor. It was found that MgB2 doped with 10 wt% C4H6O4 and sintered at 900 degrees C exhibited excellent J(c) above 10(4) A cm(-2) at 5 K and 8 T. Impurity scattering due to C substitution, improved crystallinity and the least amount of MgO in 10 wt% doped sample improves J(c) very significantly. The MgO amount is rapidly increased in 20 and 30 wt% doped samples which causes a strong depression of J(c), H-c2, H-irr due to poor inter and intra-grain connectivity.