In situ high-energy synchrotron x-ray diffraction investigation of phase formation and sintering in MgB2 tapes

In the present paper we report an in situ high-energy x-ray diffraction analysis of MgB2 tapes during the preparation process. The experiment was performed in a specifically designed furnace working in a reducing atmosphere, compatible with the Laue diffraction condition. The MgB2 synthesis was realized starting from MgH2 and amorphous B in powder form as precursors, varying reaction temperature and testing different cooling processes. We analysed both the MgB2 synthesis and the sintering process of tapes prepared with these powders. Phase evolution, micro- and crystallographic structure were monitored during the different thermal treatments. Among the main results we observed the formation of MgB2 at an extraordinary low temperature (300 0C), probably as a result of a solid-state reaction between MgH2 and B. Furthermore, we studied the dependence of the microstructure upon the thermal treatment and its effect on the critical current performance of the superconducting tapes.