Effect of grain size and doping level of SiC on the superconductivity and critical current density in MgB2 superconductor

摘要

SiC doped MgB2 polycrystalline samples were fabricated by in-situ reaction using different grain sizes (20 nm, 100 nm, and 37 μm) of SiC and different doping levels (0, 8, 10, 12, 15 wt%). Phases, microstructures, superconductivity, critical current density and flux pinning have been systematically investigated using XRD, SEM, TEM, and magnetic measurements. Results show that grain sizes of the starting precursors of SiC have a strong effect on the critical current density and its field dependence. The smaller the SiC grains are, the better the Jc field performance is. Significant enhancement of Jc and the irreversibility field Hirr were revealed for all the SiC doped MgB2 with additions up to 15 wt%. A Jc as high as 20,000 A/cm2 in 8 Tesla at 5 K was achieved for the sample doped with 10 wt% SiC with a grain size of 20 nm. Results indicate that the nano-inclusions and substitution inside MgB2 are responsible for the enhancement of flux pinning.