Influence of oxygen on the structural stability and superconducting properties of ceramic (Bi,Pb)2Sr2Ca2Cu3Oδ

By post-annealing ceramic samples in various partial pressures of oxygen, the structural stability and superconducting properties of (Bi,Pb)2Sr2Ca2Cu3Oδ are demonstrated to be sensitive to δ. The small decrease of Tc with increasing oxygen partial pressure is in agreement with previously reported results on Pb-free samples and may be connected to an optimization of the charge carrier concentration. The collapse of the 2223 phase when post-annealed above 700 °C in pure argon is also documented. It is suggested that this decomposition and the stabilization of the 2223 phase by Pb substitution are both related to the amount of oxygen contained in the (Bi,Pb)-O layers which separate the Sr-Ca-Cu-O perovskite units.