In-situ synchrotron diffraction studies of sythesis of superconducting tapes

The development of HTS wires and tapes has reached a level where they are, in principle, ready for use and various demonstration units have been tested worldwide. However, an improvement of their performance is still needed to allow for a broad market penetration. Since the characteristics of the final product are strongly dependent on the manufacturing process, detailed investigations of the phase and microstructure evolution under actual processing conditions are rather useful. However, due to the presence of the metal sheath, in-situ studies are not possible with standard techniques. Removing the sheath, even locally, would result in erroneous conclusions due to material evaporation during processing (Pb in the case of (Bi,Pb)₂Sr₂Ca₂Cu₃O₁₀ tapes and Mg in MgB₂ wires for example). Fortunately, synchrotron radiation provides a mean of overcoming this drawback by being penetrating enough to probe the HTS ceramic core of the samples. Using a two-dimensional detector, it is possible to obtain information about the texture and concentration of the dominant crystalline phases from a single exposure, which typically may be acquired within 1 to 60s. 


Overall view of the BW5 beamline with the 2D detector (left in front) and furnace (middle).


Our synchrotron studies are conducted at the DESY-HASYLAB synchrotron facility on beamline BW5 with a 77 to 100 keV incident beam depending on the sample. Short pieces of wires or tapes (@ 3 cm length) are clamped in a high-temperature steel holder inserted in a quartz tube. The sample holder assembly is placed in a high-temperature furnace equipped with capton windows and a stainless steel heat shield with holes for beam entrance and exit. The samples are maintained in a flow of gas with suitable composition during the high temperature runs.