Relationships between Oxygen Content, Modulation Period and Superconducting Property of Bi-Based Superconducting Oxides

Abstract

The influences of oxygen contents on the structural parameters and superconducting properties of Pb-doped Bi-Sr-Ca-Cu-O samples (2223 and 2212 phases) were examined. Temperatureprogrammed-desorption (TPD) measurements revealed that sorption and desorption of small amounts of oxygen (2-3 x10^-5 mol/g) took place reversibly for both samples below 600 °C (Figs.3, 8). The lattice parameter along c axis and the structural modulation period along b axis in each sample were found to increase as oxygen content decrease and vice versa (Figs.5, 7). These reversible changes in structural parameters could be explained to r esult from the desorption and sorption of excess oxygen in Bi-O layer. The dependence of T, on the oxygen content for the 2223 sample was quite different from that for the 2212 sample, i. e., with decreasing the oxygen content T_, of the former decreased by 15 K from 111 K to 96 K, while the latter increased (Figs.4, 9). These results suggest that for both samples T_, is related with the hole concentration in Cu0₂ plane which is controlled by oxygen co ntent.