Oxygen Kinetics And Superconductivity In The High-tc Oxide Yba2cu3ox

Disk-shaped samples of the nominal compositions YBa2Cu3O7, Y2BaCuO5, and BaCuO2 were initially produced through the solid diffusion method. These samples were then cut into several small pieces, which were used for oxygen intercalation and desorption studies for temperatures between 330°C and 700°C. The compound YBa2Cu3Ox went through a gradual transformation, going from the pure superconducting orthorhombic phase (x = 7.0) to the pure semiconducting tetragonal phase (x = 6.3). The compound BaCuOy also varied its oxygen content, in the range 2.00 < y < 2.08. The compound Y2BaCuO5 did not allow any variation in its oxygen content, although small mass losses were measured. The critical temperature (Tc) for YBa2Cu3Ox shows a plateau around 70 K for 6.6 < x < 6.8, though a very sharp transition is observed for the parent sample (x = 7.0) at Tc = 93 K. It is argued that the plateau is related to a phase having a metastable configuration for the oxygen vacancies.2522171217