EFFECT OF SB DOPING ON CRITICAL-CURRENT DENSITY IN BI(PB)-SR-CA-CU-O HIGH-TC SUPERCONDUCTORS

In this paper we report our results on the effect of Sb-doping on the superconducting proper-ties of the compound Bi1.6-xSbxPb0.4Sr2Ca2.2Cu3 .5Oy for x=0.0, 0.1 and 0.2. Through a series of experiments it is sho wn that the small addition of Sb (x=0.1) increases the 2223 phase frac tion and enhances T(c) as well as intergrain J(c), provided that the s intering parameters are carefully optimized. Thus, for example, the co mposition Bi1.5Sb0.1Pb0.4Sr2Ca2.2Cu3.5Oy sintered at 830-degrees-C for 12 h has a T(c0) (zero resistivity)=108 K, a drop in the chi'-T plot at 108 K and in intergrain J(c)=695 A/cm2 (as estimated on the basis o f Clem's model). Any lowering of sintering temperature below 830-degre es-C or prolonging of sintering at 830-degrees-C leads to a degradatio n in the superconducting parameters. Similarly, a reduction in T(c) an d J(c) is observed if Sb concentration is increased to 0.2. The sinter ing parameters (temperature and duration) thus appear to be critical f or a given composition.