INFLUENCE OF SILVER AND EXCESS COPPER ON THE FORMATION AND PROPERTIES OF 2223 (BI,PB)-SR-CA-CU-O SUPERCONDUCTOR

The effect of silver additions and excess copper on the sinterability and weak link behavior has been studied in the nominal composition Bi1.72Pb0.32Sr2Ca2Cu3O(x) (Ag = 1-4 wt.%) and Bi1.72Pb0.32Sr2Cu3+yO(x) where y = 0.2-0.5, using magnetic susceptibility, XRD, and SEM methods. Ag additions enhance the weak link behavior, giving a magnetic susceptibility shoulder at 103 K. This shoulder became more prominent at high fields (35 Oe), and a low T(c) phase became evident with 4 wt.% Ag additions. In contrast to stoichiometric compositions, samples containing excess copper demonstrated an enhancement of the sinterability and a large volume of 2223 phase even in calcined samples. XRD data and SEM analysis failed to detect any Cu-rich phase up to copper contents y = 0.4. However, in copper samples with y = 0.5, a small x-ray peak at 2-theta = 48.5-degrees has been observed corresponding to CuO.