[continued from p. 136]
Dwight L. Myers, M. Shane Pennington, and Jimmy Simpson,
Department of Chemistry, East Central University, Ada, OK 74820
Vapor pressures of oxygen over the REBa2Cu3O7-x (RE=Y, Er, and Yb) superconductors are being determined in our laboratory. Because of its relative simplicity and low cost of construction, the transpiration method has been chosen as the principal tool for vaporization studies. Oxygen contents of the original samples were determined using the method of Appelmann et al.1 Oxygen stoichiometries after the transpiration experiments were inferred using the mass losses observed. The data show good agreement at low temperatures with published data for the yttrium superconductor2. The calculated vapor pressure for oxygen in equilibrium with YBa2Cu3O6.97 at 573 K is 6.8 x 10-6 atm. For ErBa2Cu3O6.89 the vapor pressure of O2 at 553K is 4.2 x 10-6 atm and for YbBa2Cu3O6.91 the vapor pressure of oxygen at 640 K is 3.74 x 10-5 atm.
1. Appelman, L.R. Morss, A.M. Kini, U. Geiser, A. Umezawa, G.W. Crabtree, and K.D. Carlson, Inorg. Chem. 26, 3237 (1987).
2. Kishio, K., J. Shimoyama, T. Hasagawa, K. Kitizawa, and K. Fueki, Japn. J. App. Phys. 26 L1228-30, (1987)