MgB₂multifilamentary tapes: microstructure, chemical composition and superconducting properties

Multifilamentary Ni-sheathed Cu-stabilized MgB2 tapes with a critical current density of 2.0 × 105 A cm−2 (at 20 K and 1 T) were prepared by a powder in tube technique, using pre-reacted MgB2 powders. The microstructure and chemical composition of the superconducting core and the MgB2–Ni interface were studied using SEM, EPMA and TEM. A quick, reliable and standard-less method of B quantification using SEM-EDX is established for the analysis of MgB2 wires and tapes. Carbon-contamination-free sample preparation was crucial for the analysis of boron.