Macro-thermogravimetrical investigations of the O2 exchange during phase formation in BSCCO(2223) tapes with Ag, AgMg, AgAu sheaths or SrCO3 or SrZrO3 barriers

Oxygen exchange of BSCCO with the annealing atmosphere through the tape sheath plays an important role in the formation of BSCCO during the reaction heat treatment. Change of the oxygen support is expected to be responsible for reduced superconducting performance of conductors with alloyed sheath materials or modified configurations as BSCCO tapes with AgMg and AgAu sheaths as well as with interfilamentary resistive barriers (AC conductors). In those tapes the change in oxygen content was monitored during the first heat treatment by means of a macro-thermogravimetrical method suitable for long sample lengths. The main result is that highly alloyed AgMg sheaths and especially barrier tapes hinder significantly the oxygen diffusion during BSCCO(2223) formation. A correlation with the BSCCO phase evolution and the achieved transport currents was tried