ON A NEW COMPOUND IN THE SYSTEM BA LN/ZN/ PT/O - BA4SM4ZN3PTO15/

Reactions of mixtures of BaCO3, ZnO, Sm2O3 (3 : 5 : 1) heated in plati num crucibles up to 1250 degrees C led to big black single crystals of Ba4Sm4Zn3PtO15. The new compound crystallizes with hexagonal symmetry , space group C-6v(4),-P6(3)mc, a = 11.657, c = 6,789 Angstrom, Z = 2. It is isotypic with Ba(6)Nd(2)Al(4)O15 but shows an ordered Pt4+ and Zn2+ distribution over the aluminium positions. The octahedrally coord inated barium sites of the Ba6Nd2Al4O15 type are occupied by Sm3+. In comparison to compounds of the composition Ba(6)Ln(2)M(4)O(15) (M = Al Fe, Co), Ba4Sm4Zn3PtO15 is the first example containing different oxi dation states at the M(3+) positions.