Phase equilibria were studied in the Sr-Ca-Cu-O system by annealing samples at
1153K in Ar-O2 gas mixtures. The stability ranges of the oxide solid solutions
were observed by X-ray diffraction measurements especially at 4 compositions in
12 gas mixtures. 4 sets of invariant 4-phase equilibrium and their oxygen
partial pressure, PO2, were deduced from the surrounding 3-phase equilibria.
The compositions of the related phases were evaluated by combining EDX analysis
and the sample compositions. These results are compared with equilibrium
calculations based on thermodynamic modelling.