Effect of Sb doping on critical current density in Bi (Pb)-Sr-Ca- Cu-O high- Tc superconductors

Abstract

In this paper we report our results on the effect of Sb-doping on the superconducting properties of the compound Bi 1.6- x Sb x Pb 0.4Sr 2Ca 2.2Cu 3.5O y for x=0.0, 0.1 and 0.2. Through a series of experiments it is shown that the small addition of Sb ( x=0.1) increases the 2223 phase fraction and enhances T c as well as intergrain J c, provided that the sintering parameters are carefully optimized. Thus, for example, the composition Bi 1.5Sb 0.1Pb 0.4Sr 2Ca 2.2Cu 3.5O y sintered at 830°C for 12 h has a T c0 (zero resistivity) = 108 K, a drop in the χ'- T plot at 108 K and in intergrain J c=695 A/cm 2 (as estimated on the basis of Clem's model). Any lowering of sintering temperature below 830°C or prolonging of sintering at 830°C leads to a degradation in the superconducting parameters. Similarly, a reduction in T c and J c is observed if Sb concentration is increased to 0.2. The sintering parameters (temperature and duration) thus appear to be critical for a given composition.