CRYSTALLIZATION FIELD INVESTIGATION OF THE (Bi, Pb)-Sr-Ca-Cu-O SYSTEM. Lawrence P. Cook, Winnie Wong-Ng, Ceramics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899

Knowledge of melting equilibria in the system Bi-Sr-Ca-Cu-O is important for processing of superconductor tapes and wires, and for melt growth of single crystals. Experimental difficulties associated with the melting studies of the copper containing high T_c superconductor phases are corrosion of containers and atmospheric contaimination. Furthermore, the large crystals formed during quenching of melt render the determination of primary crystals and melt compositions difficult. By using a wicking technique to capture the melt and performing quantitative microchemical analysis, melt compositions have been obtained for important melting reactions involving four or five solids. This data allows construction of the multidimensional crystallization fields for various solids in the system.

Discussion will include melt evolution of the BiSr-Ca-Cu-O system, approximate crystallization fields of the "2122" and "2223" high T_c phases, and melting characterization of the Raveau phase (commonly referred to as the "2201" phase). The effect of Ag addition on melting equilibria will also be discussed.