Significant enhancement of Jc of MgB2 by doping organic carbon with chemical solution methods

MgB2 superconductors have the potential for application at 20 K, and improving their superconducting current carrying capacity is the key to achieving this application. In this article, the doping effects of organic carbon (citric acid, C6H8O7) on the critical temperature (Tc), critical current density (Jc), and irreversible field (Hirr) of MgB2 was studied, in order to explore the path of improving its superconducting performance at 20 K. Combing hot -pressing sintering and chemical solution route for making the samples, it was observed that a moderate level of doping (10 wt%) significantly improved the Jc of MgB2 at 20 K: the 2 T -infield Jc of 10 wt% doped sample reaches a value of 30400 A/cm2, increased by 56.7% compared to the undoped sample. The mechanism beneath the improved performance is studied and attributed to the rapidly enhanced delta l-type flux pinning force brought about by partial substitution of C for B. In addition, the grain refinement effect caused by C doping strengthens the surface pinning force, resulting in a better agreement between the scaling behavior of the pinning force density and the theoretical model of surface pinning.