FORMATION OF HIGH-T-C PHASE IN SN-INCORPORATED (BI,PB)-SR-CA-CU-O SUPERCONDUCTING SYSTEM

Superconductor Bi2Pb1-xSnxSr2Ca2Cu3Oy (x = 0.0, 0.05, 0.08, 0.1, 0.2 a nd 0.3) samples were prepared by the conventional solid state reaction and analyzed by XRD, SEM, TGA and DSC and their resistivities were me asured by standard ac four-probe method. When a small quantity of Sn ( x<0.1) was added, it was found from the SEM and XRD results that high- T-c phase occurred preferentially and the critical temperature was ele vated. With the results of XRD, EDX, DSC and TG, it was concluded that a small amount of Sn promotes the formation of liquid phase, which ma kes the weak link of grain boundary better. When a large amount (x gre ater than or equal to 0.1) of Sn was added to the (Bi,Pb) 2223 system, however, the solid state reactions became more important than liquid phase-assisted reactions. Thus, the reaction rate decreased and there is no longer a significant role of tin on the formation of 2223 phase in that region (0.1 less than or equal to x less than or equal to 0.3) . (C) 1998 Elsevier Science S.A. All rights reserved.