Abstract:

Two new compounds, Sr6Sb4Co3O14(OH)10 (SSC) and Sr6Sb4Mn3O14(OH)10 (SSM), were synthesized under hydrothermal conditions in an alkaline medium. Their structures were determined by powder X-ray diffraction using Rietveld analysis, and the topology of the metal cation network was discussed. These two isostructural compounds crystallize in a garnet-related or hydrogarnet-related structure with the space group I43d and the lattice parameters (a) are 1.30634(2) nm(SSC) and 1.31367(1) nm(SSM). The SbO6 octahedron and MO4 (M=Co, Mn) tetrahedron share corners with each other to formthe backbone of the structure. The topology of the Sb5+ andM2+ (M=Co,Mn) network is ctn, which is the C3N4network. The Sb5+ node is three-connected and that of M2+ (M=Co, Mn) is four-connected. The distribution of the M2+ (M=Co, Mn) cations in the structure is in a fanlike mode with a thp topology, i.e., a network of Th atoms in Th3P4. These two compounds are antiferromagnetic. Sr6Sb4Co3O14(OH)10 exhibits a net magnetic moment, which may be related to the canting ordering of Co2+ ions below 10 K. Sr6Sb4Co3O14(OH)10 and Sr6Sb4Mn3O14(OH)10 decompose above 300 ℃ and give rise to the perovskite-type compounds Sr2(Sb, M)2O6(M=Co, Mn) as the main phases in the products after treatment at 900 ℃ under atmospheric conditions.

Key words: Topological structure, Hemi-hydrogarnet, Hydroxyl oxide, Rietveld structure refinement, Antiferromagnetic