Effect of Sintering Temperature on the Superconducting Properties of Graphene Doped $\hbox {MgB}_{2}$

A comprehensive study on the effects of sintering temperature on graphene-doped MgB₂ superconductor was conducted. Graphene has emerged as an effective dopant that is capable of improving the critical current density (J_c) and flux pinning at a very low doping level, with only a slight reduction of the critical temperature (T_c). MgB₂ undoped and graphene-doped bulk samples were prepared by the in situ method and sintered within a temperature range from 650 to 950 ^°C. It is surprising to note that at the doping level of 1 at.% the sample sintered at 850 ^°C shows a J_c of 5.6 ×10³ A/cm², which is nearly two times higher than that of the undoped sample, with a slight reduction in T_c of 0.5 K. The effects of the sintering temperature on the lattice parameters, resistivity, grain to grain connectivity, lattice disorder, and critical fields have also been investigated. The results are compared with those for undoped samples subjected to the same sintering conditions, and the origins of the differences in the critical current density are discussed.