INFLUENCE OF CARBON ON THE FORMATION AND THE MICROSTRUCTURE OF B(P)SCCP-110-K-PHASE IN AG-SHEATHED TAPES

To investigate the influence of carbon on the formation and microstructure of B(P)SCCO-110-K-phase in Ag-sheathed tapes, powder in tube tape samples were prepared with calcined oxide-carbonate mixtures containing different amounts of carbon. The thermochemical behaviour of the samples was studied by quenching experiments in the early stage of the heat treatment. Appearance of 2201 phase in the as-quenched tapes indicates the existence of melt during the heat treatment. Melting of the ceramic core is considerably influenced by carbon. The onset of partial melting is reduced from 820 to 825 degrees C in carbon poor samples to 810 degrees C in carbon rich samples. Ai these temperatures alkaline-earth cuprate, 2212, and melt, present as 2201 in quenched tapes, seem to coexist. Formation of 2223 phase appears to be a three step process. After a rapid solid state transformation from 2201 to 2212 and the partial formation of liquid, the 2223 reaction takes place in the presence of melt.