Stability limits of the perovskite structure in the Y-Ba-Cu-O system

The equilibrium (molecular) oxygen partial pressure of the Y1Ba2Cu3O7−x phase has been measured by an electrochemical method. The investigations are focused on the low-temperature range between 560 and 750 °C and on oxygen stoichiometries close to the oxygen-poor phase boundary. In particular, the oxygen partial pressure has been determined below which the perovskite structure becomes thermodynamically unstable. This critical value should be considered during the preparation of high Tc Y1Ba2Cu3O7−x superconductors, especially in the case of an in situ preparation of thin films.