Influence of silver and excess copper on the formation and properties of 2223 (Bi, Pb)–Sr–Ca–Cu–O superconductor

Abstract

The effect of silver additions and excess copper on the sinterability and weak link behavior has been studied in the nominal composition Bi1.72Pb0.32Sr2Ca2Cu3Ox (Ag = 1−4 wt. %) and Bi1.72Pb0.32Sr2Cu3+yOx 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 Tc 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 2θ = 48.5°has been observed corresponding to CuO.