LOCAL PHASE EVOLUTION IN (PB BI)(2)SR2CA2CU3OX TAPES/

The phase evolution has been measured locally from the core-sheath int erface to the core-centre of(Pb/Bi)2223 tapes sintered for up to 350 h . The rate of the phase conversion is found to be much faster at the i nterface than at the centre. For example, in a tape sintered at 832 de grees C in air for 30 h, the percentage of 2223 phase is similar to 90 % at the interface compared with similar to 27% at the centre. Consequ ently, there is a 2223 phase gradient from the interface to the centre of the core, even after a long sintering time. There appears to be an associated gradient in the grain size and Vicker's microhardness acro ss the thickness of the core. The influence of the silver sheath on th e phase conversion in half-peeled tapes has also been studied. The hal f-peeled tapes were made by removing one side of the silver sheath of the normal (Pb/Bi)2223 tape before sintering.