The effect of ZrSi₂ and SiC doping on the microstructure and J_c-B properties of PIT processed MgB₂ tapes

We investigated the effect of ZrSi₂ and SiC doping on the microstructure, critical current density J_c and flux pinning of Fe-sheathed MgB₂ tapes prepared by the in situ powder-in-tube method. Heat treatment was performed at a low temperature of 650 °C for 1 h. The phases, microstructures and flux pinning were characterized by means of x-ray diffraction, scanning electron microscope, magnetic and transport property measurements. It was found that the tapes doped with nanoscale SiC had the best pinning performance, while the ZrSi₂ powder showed a similar improved field dependence of J_c compared with undoped samples. J_c values for the SiC doped samples were enhanced by two orders of magnitude at 4.2 K in magnetic fields above 8 T. At 4.2 K and 10 T, the J_c reached ∼1.5 × 10⁴ A cm^-2. Moreover, the critical temperature for the doped tapes decreased slightly (<1.2 K). Microstructural analysis shows that very good grain connections or/and grain refinement were obtained for the doped tapes. The mechanism of the enhancement of the flux pinning is also discussed.