Electron microscopic and metallographical investigations on superconducting MgB2 tapes with mechanically alloyed precursor powder

Magnesium diboride is a cost-efficient superconducting material with a transition temperature of 40 K. Technical conductors as wires or tapes were prepared as composite of the ceramic superconductor and a metallic sheath using the powder-in-tube (PIT)-technology. High energy milled powder consisting of Mg, B and partially reacted MgB2 is used as precursor. Metallographical and electron microscope (SEM) investigations at tapes prepared with different precursor powders or sheath materials contribute to optimize the conductors and to draw conclusions for the processing of the tapes. Optimized tapes are characterized by a critical current density of 10(4) A/cm(2) at 4.2 K and 10 T.