Cooling behavior of BSCCO/Ag tapes.

The phase transformations taking place during cooling of BSCCO/Ag tapes have been in,investigated by means of high energy x-ray diffraction at a synchrotron source. This technique allows in-situ measurements of the concentration changes of the major structural phases, including liquids, In addition, information is obtained on stoichiometry and texture variations. Two mono-filament tapes were studied in air. The first tape was cooled at a constant rate of 50 degrees C/h, At temperatures above 730 degrees C the (Ca,Sr)(2)CuO, and liquid phases are almost completely converted to 2212 and 2223, Below 780 degrees C a Pb-rich phase appears, either 3221 or (Ca,Sr)(2)PbO4. Simultaneously, shifts of x-ray lines indicate that 2223 is deprived of Pb, and from 730 OC onwards the concentration of 2223 drops. The second tape was cooled in steps to sequentially lower temperatures: 845 degrees C, 820 OC and 660 degrees C. At the former two steps (Ca,Sr)(2)CuO3 and liquid phases are again converted to 2212 and 2223, while at 660 degrees C they are rapidly converted to 2212 and primarily - 2201, Also at 660 degrees C, 2223 decomposes to 3221 or (Ca,Sr)(2)PbO4 at a rate of of 40 % per hour.