Comparison on Effects of B4C, Al2O3, and SiC Doping on Performance of MgB2 Conductors

Several MgB2 monofilamentary samples are prepared to evaluate the effects that the doping compounds B4C, Al2O3, and SiC have on critical current density (J(c)) and the J(c) dependency of magnetic flux density (B) of the sample. All of the samples in this study have Nb sheaths and are manufactured using in situ precursor powders and the Powder-in-Tube fabrication method. The amounts of added impurities are 10 wt.% for B4C and Al2O3, and 3, 10, and 20 wt.% for SiC. A reference sample without any doping is also prepared. All of the samples are heat treated between 650 and 800 degrees C for 30 minutes. The transport J(c)(B) characteristics are measured at 4.2 K and the magnetic J(c)(B) behavior is obtained in varied temperatures up to 30 K. The changes in connectivity, or effective cross-section, are also evaluated by performing resistivity measurements on the samples after removal of the sheath. Furthermore, the pinning forces of the samples are evaluated from the magnetic measurements.