EFFECT OF SINTERING TEMPERATURE ON THE SUPERCONDUCTIVE PROPERTIES OF BI(PB)-SR-CA-CU-O CERAMICS

AC susceptibility and X-ray diffraction techniques have been used to investigate the superconductive and structural properties in the system Bi 2-xPbxSr2Ca2Cu3O y with x=0, 0.2, 0.4 and 0.6, and sintered in air at T s=860, 870 and 880 degrees C for 40 h. The best bulk superconductive properties (zero resistance below 103 K) were obtained with x=0.4 and T s=860 degrees C. Tc of the granular 2223 phase remained constant at 107 K, independent of x and Ts. A higher Ts increases the proportion of the high-Tc (2223) phase relative to the low-Tc (2212) phase. However, the occurrence of partial melting is detrimental to both the intergranular coupling and the bulk-Tc values of these ceramic samples and may also lead to the formation of two coexisting low-Tc, 2212 subphases, when x=0.6.