Sm2O3Ga2O3 and Gd2O3Ga2O3 phase diagrams

Abstract Four definite compounds exist in the Sm 2 O 3 Ga 2 O 3 binary phase diagram, namely: Sm 3 GaO 6 , Sm 4 Ga 2 O 9 , SmGaO 3 , and Sm 3 Ga 5 O 12 . The 3 1 compound is orthorhombic (space group Pnna - Z .4) with the cell parameters: a = 11.40 0 A, b = 5.51 5 A, c = 9.07A and belongs to the oxysel family. Sm 3 GaO 6 and SmGaO 3 melt incongruently at 1715 and 1565°C; Sm 4 Ga 2 O 9 and Sm 3 Ga 5 O 12 have a congruent melting point at 1710 and 1655°C. With regard to the Gd 2 O 3 Ga 2 O 3 system three definite compounds have been identified: Gd 3 GaO 6 , Gd 4 Ga 2 O 9 , and Gd 3 Ga 5 O 12 . Only the garnet melts congruently at 1740°C with the following composition: Gd 3.12 Ga 4.88 O 12 . Gd 3 GaO 6 , and Gd 4 Ga 2 O 9 melt incongruently at 1760 and 1700°C. GdGaO 3 is only obtained by melt overheating which may yield an equilibrium or a metastable phase diagram.