Phase equilibria in superconducting oxides

The structures and properties of superconducting oxides that are observed at and below room temperature depend critically on how the materials are processed at higher temperatures. Consequently, there is a need to understand the high-temperature chemistry of these oxides. In this paper, the authors describe the use of a solid-state ionic technique to determine the thermodynamic stability of Y1Ba2Cu3O6+x and the quaternary phase relations near the compound at 850 degrees C by oxygen coulometric titration. Moreover, the authors use the same apparatus to investigate oxygen ordering and phase separation in Y1Ba2Cu3O6+x at lower temperatures by preparing samples with precisely controlled oxygen contents