1991 Volume 99 Issue 1153 Pages 774-779
Oxygen sorption-desorption behavior as well as superconducting properties were examined for four Bi-based oxides (2212 phase, Bi2-xPbxSr2-yCa1+yCu2O8+δ: (x, y)=(0, 0), (0, 0.8), (0.2, 0), (0.2, 0.8)). Temperature-Programmed-Desorption (TPD) mesurements revealed that reversible sorption and desorption of small amounts of oxygen (ca. 2-3×10-5mol/g) were observed for all the samples below 600°C. The Tc and lattice parameters (c) were found to change reversibly with the oxygen content. The oxygen content dependence of Tc for the y=0 sample was quite different from that for y=0.8, i.e., Tc increased with decreasing oxygen content in the former, while in the latter Tc decreased. On the other hand, the oxygen content dependence for x=0 was similar to that for x=0.2. The optimum oxygen content (hole concentration) for the highest Tc in Bi2Sr1.2Ca1.8Cu2O8+δ was confirmed to be δ=0.15.
