X-ray- and thermographic study of compounds in the BaO-Sc2O3 system

The BaO-Sc2O3 system is studied using the X-ray graphic and thermogpaphic methods. Three ind+vidual compounds of the compositions Da2c2O5+ Ba3Sc4O9 and BaSc2O4 are formed in the system. Ba3Sc4O9 and Ba c2O4 are melted congruently at 2050 and 2100 deg respectively. Ba2Sc2O5 decomposes in the solid state at 1000 deg into Ba3Sc4O9 and BaO. Three eutectics are found in the system. Ba2Sc2O5 is crystallized in tetragonal crystal system with the lattice parameters: a=4.160 (1), c=3.984 (1)A. Hexagonal lattice of Ba3Sc4O9 has the following parameters: a=5.873 (1), c=23.69 (1)A, sp. gr. R anti 3 m. BaSc2O4 is crystallized in monoclinic crystal system with the parameters: a=9.836 (1), b=20.578 (3), c=5.8147 (3)A, sp.gr B2/b. The types of scandium and barium coordination in scandate are ScO6 octahedrons, BaO12 cubical octahedrons and their hexagonal analogues