In situ x-ray and neutron diffraction investigation of Bi-2212 in multifilamentary wires during thermal treatment

Significant insights for critical current density (J(c)) improvement in Bi-2212 superconductor wires can be obtained by an accurate analysis of the structural and micro structural properties evolving during the so-called partial-melt process, a heat treatment needed to improve gram connectivity and therefore gain high J(c). Here, we report an in situ analysis by means of synchrotron x-ray and neutron diffraction performed, for the first time, during the heat treatment carried out with the very same temperature profile and reacting oxygen atmosphere in which the Bi-2212 wires are usually treated for practical applications. The obtained results show the thermal evolution of the Bi-2212 structure, focusing in particular on texturing and secondary phases formation. The role of the oxygen is discussed as well. Hence, the present investigation marks a significant advance for the comprehension of the phenomena involved in the wire fabrication process and provides useful insights for the process optimization as well.