Chemical reactivities of the superconducting oxides, YBa2Cu3Oy and BiSrCaCu2Oy

The chemical reactivities of YBa2Cu3Oy and BiSrCaCu2Oy with various gases have been studied. It was found that large quantities of NO, CO, and NO2 were rapidly absorbed (or intercalated) in the bulk of YBa2Cu3Oy (Tc: 90 K) at 573 K. The amount absorbed was in the order NO ∼ CO ∼ NO2 > O2 ∼ CO2 > N2O ∼ 0. The amount for NO was more than two times the amount of YBa2Cu3Oy in molar ratio and elongation by about 0.2 angstrom along c-axis was observed. NO absorbed was almost completely recovered as NO by the evacuation at 773 K. This absorption-desorption cycle proceeded reversively. The electronic resistivity at 573 K of YBa2Cu3Oy increased upon the NO absorption and was restored by the evacuation at 773 K. CO was also absorbed rapidly accompanied by evolution of CO2. BiSrCaCu2Oy did not absorb either NO or CO