Combined X-ray and electron microscopy study of MgB2 powders, wires and tapes

MgB2 wires, tapes and bulk samples produced within the EU-funded HIPERMAG project have been studied by a combination of X-ray diffraction and electron microscopy. The reaction layers forming at the interface between the ceramic core and Fe or Ni sheaths can be studied with both methods. The complementary techniques enable to study both the microstructure and the formation kinetics of the interface layers. Grain sizes can be determined either by direct observation or by analysis of the shape of X-ray diffraction peaks. Electron microscopy can detect B-rich secondary phases and phases present in small fractions that are not accessible by x-ray diffraction. On the other hand, synchrotron diffraction provides a fast and non-destructive method for the study of the main phases and their development during insitu, high-temperature investigations. The combination of the two techniques is a very valuable tool for the optimisation of MgB2-based superconducting material.