In the fabrication of MgB2 superconducting tapes, doping with nano-sized SiC is effective for enhancing the critical current density (Jc) under magnetic fields. It has been reported that the Jc enhancement is due to the formation of nano-sized silicides such as Mg2Si and the substitution of C atoms for B atoms in the MgB2 crystals. In this work, we report more effects of SiC doping on the microstructure formation in MgB2 tapes. MgB2/Fe tapes were fabricated using an in-situ powder-in-tube method with MgH2 as the precursor powder. Analytical transmission electron microscopy combined with a focused ion-beam microsampling technique was used for microstructural characterization. Overall microstructures in the tapes were characterized as densely crystallized MgB2 areas with 10-200 nm grain size, partially crystallized MgB2 areas mainly containing MgO and amorphous B-rich phases, and a number of holes and cracks. It was found that SiC doping leads to forming equiaxial granular structures of MgB2. A significant difference in the distribution of O atoms was observed between the SiC-doped and non-doped MgB2 tapes. Based on these results, mechanisms of the microstructural formation and Jc enhancement as the results of SiC doping are discussed.
