Improvement of critical current density in Fe-sheathed MgB2 tapes by ZrSi2, ZrB2 and WSi2 doping

Fe-sheathed MgB2 tapes were prepared through the in situ powder-in-tube technique by 5 at.% ZrSi2, ZrB2 and WSi2 doping, respectively. The doping effect of these compounds on the microstructure and superconducting properties of MgB2 tapes has been investigated by using x-ray diffraction, scanning electron microscope, transport measurements and DC susceptibility measurements. Compared to the undoped samples, Jc for all the doped samples were much improved; the best result in terms of Jc was achieved for ZrSi2 doping, by up to a factor of 3.4 at 4.2 K in magnetic fields up to 12 T. Moreover, these dopants did not significantly decrease the transition temperature. The Jc-B curves of WSi2-doped tapes show better performance in higher magnetic fields in comparison to undoped tapes, suggesting that pinning centers effective in a high-field region were possibly introduced.