Influence of dopant particle size on the critical current properties and microstructures of MgB2 bulks doped with TiC and SiC

The influence of dopant particle size on the critical current properties and microstructures of the TiC doped and SiC doped MgB2 bulks were studied. XRD analysis revealed that samples doped with nano-size TiC and SiC showed high actual carbon content in MgB2 lattice due to their high reactivity, while micro-size dopants of TiC and SiC were less reactive with magnesium and boron. Improvement of Jc under high fields was achieved by the nano-size TiC and SiC doping. Moreover, TiC was found to contribute to refinement of MgB2 grain size and hence flux pinning by grain boundaries was strengthened. Our results suggest that the impurity doping effects on the critical current properties of MgB2 are crucially affected by the particle size of dopants