Phase formation from liquid phase under various post-annealing conditions

The process of phase formation from the liquid phase during post-annealing process has been studied precisely using the powder XRD Rietveld analysis. Mass fraction of the liquid phase was estimated to be 9.3% from the sum of phases that formed during post-annealing. Phase conversion from the liquid phase depended strongly on post-annealing temperature and its regime is mainly divided into two patterns. The first is the conversion into (Bi,Pb)2212 and CaPbO/sub 4/ and the second is into (Pb,Bi)3221 and AEC. The former regime was observed during post-annealing at around 1073 K, whereas the latter occurred at around 1053 K. The liquid phase existed at (Bi,Pb)2223 grain boundaries is suggested to limit superconducting current path. The increase of critical current by 1.4 times after post-annealing is closely related with the crystallization of grain boundary liquid.