The phase equilibrium relations in the systems Y 2 O 3 ‐Al 2 O 3 and Gd 2 O 3 ‐Fe 2 O 3 were examined. Each system has two stable binary compounds. A 3:s molar ratio garnet‐type compound exists in both systems. The 1:1 distorted perovskite structure is stable in the system Gd 2 O 3 ‐Fe 2 O 3 but only metastable in the system Y 2 O 3 ‐AI 2 O 3 . This interesting example of metastable formation and persistence of a compound with ions of high Z/r values explains the discrepancies in the literature on the structure of the composition YA1O 3 . A new 2:1 molar ratio cubic phase has been found in the system Y 2 O 3 ‐A1 2 O 3 . Since silicon can be completely substituted for aluminum in this compound, the aluminum ions are presumably in fourfold coordination.
L. RöschJoachim PickardtSigrid ImmeUte Börner
W. BuchmeierB. EngelenH. D. Lutz
Patrick WoidyAntti J. KarttunenFlorian Kraus
M. MöhlenB. NeumüllerN. FazaChrista E. MüllerWerner MassaKurt Dehnicke