Mechanism of oxygen incorporation in the YBa2Cu3O6.9 superconductor

It is well known that the oxygen content exherts a critical role in determining the electrical characteristics of the perovskite cuprate superconductors. However, the formal oxidation state of copper in the compounds as well as the mechanism of oxygen incorporation in their structure, are still a matter of discussion. In this work, we propose two possible disorder equilibria in the 400°C to 525°C temperature range and attempt to substantiate them by experimental evidence.