Phase Compatibilities in the System Y 2 O 3 ‐BaO‐CuO at 950°C

We report the compatibility relationships between compounds, including the newly discovered superconducting Y 1 Ba 2 Cu 3 O x phase, in the Y 2 O 3 ‐BaO‐CuO system at 950°C. In addition to the previously reported ternary compounds, there is a new compound with a composition Y l Ba 3 Cu 2 O x . The new compound is a perovskite 'space group P4mm) with lattice parameters a =4.078 Å (0.4078 nm) and c =4.01 Å (0.401 nm). There are also at least two structurally distinguishable binary phases between barium oxide and the known BaCuO 2 , but they appear to be hygroscopic and are beyond our current capabilities of analysis.