Article

Effects of MgO impurities and micro-cracks on the critical current density of Ti-sheathed MgB2 wires

Department of Physics, Sam Houston State University, 1908 Ave. J, Huntsville, TX 77341, USA; Department of Mechanical Engineering, University of Houston, 4800 Calhoun Road, Houston, TX 77204, USA; Texas Center for Superconductivity, University of Houston, Houston, TX 77204, USA; Department of Chemistry, University of Houston, Houston, TX 77204, USA
Physica C: Superconductivity 01/2007; DOI: 10.1016/j.physc.2007.02.013

ABSTRACT Ti-sheathed monocore MgB2 wires with improved magnetic critical current density (Jc) have been fabricated by in situ powder-in-tube (PIT) method and characterized by magnetization, X-ray diffraction, scanning electron microscopy and electrical resistivity measurements. For the best wire, the magnetic Jc values at 5 K and fields of 2 T, 5 T, and 8 T are 4.1 × 105 A/cm2, 7.8 × 104 A/cm2, and 1.4 × 104 A/cm2, respectively. At 20 K and fields of 0.5 T and 3 T, the Jc values are about 3.6 × 105 A/cm2 and 3.1 × 104 A/cm2, respectively, which are much higher than those of the Fe-sheathed mono-core MgB2 wires fabricated with the same in situ PIT process and under the same fabricating conditions. It appears that the overall Jc for the average Ti-sheathed wires is comparable to that of the Fe-sheathed wires. Our X-ray diffraction and scanning electron microscopy analysis indicates that Jc in the Ti-sheathed MgB2 wires can be strongly suppressed by MgO impurities and micro-cracks.

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