THE TERNARY-SYSTEM BAO-CAO-CUO-O

Subsolidus equilibrium relationships are determined among the phases of the BaO-CaO-CuO-O system at 900-degrees-C in oxygen. Two new ternary compounds are detected: Ba4CaCu3O8.25 (cubic, a(o) = 8.157 angstrom) and Ba6CaCu3O10.5 (tetragonal, a(o) = 4.055 angstrom, c(o) = 21.605 angstrom) while a solid solution field is evidenced as originating from BaCuO2+delta by the substitution of Ca for Ba up to a limit of about 8 at%. X-ray powder diffraction analysis shows that the above two phases are isostructural with the corresponding ones originating in the basic zone of the system BaO-Y2O3-CuO-O with composition Ba4YCu3O9 and Ba6YCu3O11.