Effects of Pb in the first stages of the Bi(2223) phase formation

The reaction of the precursor powders necessary for the formation of the final Bi(2223) phase was investigated with and without the presence of an Ag sheath by means of differential thermogravimetry (DTA/DTG). The nature of the endothermic peaks observed by DTA as well as the influence of Ag on their positions are discussed. By means of X-ray diffraction and energy dispersive X-ray analysis (EDX) on oil-quenched Ag-sheathed tapes it is shown that the Bi(2212) phase originally present in the precursor powders undergoes a structural modification which can be associated with the dissolution of Pb. This transformation occurs at a temperature near 836 degrees C in Ag-sheathed tapes. This work has been essentially focused on the role of Pb and its effects on the Bi(2212) phase in the first stages of transformation.