SYNTHESIS AND CRYSTAL-STRUCTURE OF HOLLANDITE-RELATED VANADIUM-DEFICIENT SOLID-SOLUTION BAV10-XO17 (0.10-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.65)

New vanadium-deficient solid solution, BaV10-xO17 (0.10 less-than-or-equal-to x less-than-or-equal-to 0.65), was discovered by an solid state reaction at 1473 K under normal pressure. For BaV9.89O17; M(r) = 913.128, monoclinic, I2/m, a = 10.8130(12) angstrom, b = 2.9034(1) angstrom, c = 9.4640(9) angstrom, beta = 92.417(5)-degrees, V = 296.85(4) angstrom3, Z = 1, D(x) = 5.108 Mg m-3, mu = 10.54 mm-1, F(000) = 419.47, T = 295 K, lambda(MoKalpha) = 0.71073 angstrom, final R = 0.040 for 1158 unique observed reflections. V(1) and V(2) octahedra form a hollandite-type framework. Ba and O(5) atoms alternately occupy and fill up the center of the hollandite-type tunnel. The tunnel accommodates an additional V(3) atom, which is responsible for the vanadium-deficient composition. The V(3) atom forms a coordination octahedron, which distorts the tunnel strongly. Consequently, Ba and O atoms form close-packed layers chhchh ... parallel to (101), of which the c layers contain the Ba atoms. The V(3) octahedra neighbor the V(2) octahedra through face-sharing. BaV10-xO17 is closely related to the modified vanadium hollandites, A2-xV8+2xO16+x(A = K, Rb), prepared by a high-pressure synthesis. (C) 1994 Academic Press, Inc.