FE4SI2SN7O16 - A COMBINATION OF FESN6-OCT AHEDRA WITH LAYERS OF (FE3SN)O-6-OCTAHEDRA - PREPARATION, PROPERTIES, AND CRYSTAL-STRUCTURE

Fe4Si2Sn7O16 has been prepared by a solid state reaction at 900 degree s C from a mixture of Fe2O3, SnO2, Sn, and Si. The compound is a param agnetic semiconductor. Results of Mossbauer and suszeptibility measure ments as well as bond length-bond strength calculations lead to the po ssible ionic formulation Fe42+Si24+Sn12+Sn14+O162-. The compound cryst allizes in the trigonal space group P (3) over bar m1 (no. 164), with one formula unit per cell. Lattice parameters obtained by powder measu rements are: a = 6.8243(6)Angstrom, c = 9.1404(6) Angstrom, gamma = 12 0 degrees, V = 368.6(1) Angstrom(3). The structure consists of layers of edge linked oxygen octehedra exactly centered by Sn and Fe in the r atio 1:3. Three plains of isolated SiO4 tetrahedra, FeSn6 octahedra an d again SiO4 terahedra are inserted between two such layers. The layer s are stacked along [001] and linked three-dimensionally by oxygen.