Synthesis, crystal structure, and physical properties of Sr0.93(SixNb1-x)Nb10O19 (x=0.87)

We present here the synthesis, crystal structure, and physical properties of a reduced niobium oxide Sr-0.93(SixNb1-x)Nb10O19 (x = 0.87), Its structure was determined on single crystal by X-ray diffraction in the space group R (3) over bar (a(h) = 7.843(1), c(h) = 42.26(2) Angstrom, V-h = 2251.3(9) Angstrom(3), and Z = 6), The compound is isostructural to Na(SixNb1-x)Nb10O19 (x approximate to 0.75) and exhibits discrete [Nb6O12] Clusters, Nb2O10 dimers, NbO6 octahedra, SrO12 cube-octahedra, and SiO4 tetrahedra. The compound is insulating with a room-temperature resistivity similar to 50 Omega cm, The magnetic susceptibility data yields mu(eff) = 3.16 mu(B)/Nb, which is consistent with a 15-electron [Nb6O12] cluster, with Nb(IV) in the dimers and Nb(V) in the isolated NbO6 octahedra. (C) 2000 Academic Press.