Significant enhancement of Jc and flux pinning mechanism of MgB2 doped with PEG-polymers

Abstract

Compared with traditional low-temperature superconductors, the advantage of MgB2 lies in its critical temperature close to 40 K, which provides potential application at 20 K. In order to further improve its superconducting current carrying capacity at 20 K, a series of PEG polymer (including PEG2000, PEG4000, and PEG6000) doped MgB2 with doping level of 15 wt% were prepared by combining hot-pressing sintering with chemical solution route. The best result is achieved in PEG4000 doped sample, with a Jc at 20 K and 2 T reaching 51,000 A/cm2, increased by 42.8 % in comparison with the undoped sample. Study on the mechanism of the improvement reveals that organic carbon doping enhances the irreversibility field and consequently the flux pinning force. In response to the deviation of MgB2 pinning characteristics from Kramer theory, an irreversibility field increment (IFI) model was proposed which provides a satisfactory explanation for the experimental results. Our results demonstrate that the combination of hot-pressing sintering and organic carbon doping is an effective means to enhance the superconducting performance of MgB2 at 20 K for practical applications.