The change in the temperature dependence of the resistance, R(T), of ceramic YBa2Cu3O7 - x as oxygen is removed from the sample has been studied. The superconducting transition temperature shifts progressively downward in the process. There is no significant broadening of the transition. The temperature dependence of the resistivity, (T), is linear, with a progressively increasing slope, only at T > 400 K. It is suggested that oxygen condenses on Cu-O chains at T400 K.
PACS: 74.60.Mj, 74.70.Vy, 81.40.Rs, 72.80.Ga