Structural studies of BSCCO/Ag-tapes by high-energy synchrotron X-ray diffraction

Abstract

High-energy (100 keV) synchrotron X-ray diffraction has been identified as a powerful tool for characterizing texture and structural phases within Ag clad high T c superconducting tapes of the (Bi,Pb)–Sr–Ca–Cu–O (BSSCO) type during synthesis of (Bi,Pb) 2Sr 2Ca 2Cu 3O x (Bi-2223) from (Bi,Pb) 2Sr 2CaCu 2O x (Bi-2212). Using a CCD camera, the texture and concentration of the dominant structural phases can be determined simultaneously within fractions of minutes. As an example, we report on the in situ annealing behavior in air at 835°C of an as-rolled monofilament tape. It is shown that the alignment of the superconducting grains takes place almost exclusively in the Bi-2212 phase. During heating, the texture profile narrows rapidly above 750°C, coincident with the dissolution of (Ca,Sr) 2PbO 4. A 98% conversion of Bi-2212 is obtained within 19 h, but furnace cooling leads to the formation of secondary phases such as Bi-2201 and (Ca,Sr) 2PbO 4. Room temperature data on similar tapes show that subsequent deformation and annealing results in a higher Bi-2223 phase purity while slightly deteriorating the grain alignment.