High anisotropic critical current densities in MgB2 tapes

Abstract

We present a study on the angular dependence of the critical current density (Jc) of SiC-doped MgB2 tapes fabricated by powder-in tube (PIT) with stainless steel (SS) as sheath material. The microstructure and texturing of the tapes are analysed to understand the effects of the rolling degree on the superconducting properties. The microstructure is studied by x-ray diffraction and scanning electron microscopy, while Jc is measured by transport in liquid He and Ne. We found that for Si-doped tapes the alignment degree augmented with increasing deformation but tends to saturate for aspect ratios larger than 5, while the anisotropy factor JAF=Jc(90°)/Jc(0°) continued increasing for larger aspect ratios. This increase is attributed to a pinning decrease for the applied field parallel to the tape direction. Very high Jc values were obtained for Si-doped tapes, whose cores are as dense as those from wires processed using hot isostatic pressing (HIPing) by optimizing the rolling degree.