HYDROTHERMAL SYNTHESIS AND CRYSTAL-STRUCTURE OF A NOVEL BARIUM VANADIUM-OXIDE - BA0.4V3O8(VO)(0.4)CENTER-DOT-NH2O

A new barium vanadium oxide Ba0.4V3O8(VO)(0.4) . nH(2)O (n similar to 0.6) has been synthesized hydrothermally from a VOCl2-BaCl2 solution. The green-black crystal composed of elongated thin plates exhibits a monoclinic system: P2(1)/m, a = 10.153(3) Angstrom, b = 3.6329(9) Angstrom, c = 9.435(2) Angstrom, and beta = 102.10(2)degrees. Structural analysis using 951 independent reflections led to R = 0.063 and R(w) = 0.076. The structure is basically a layered type made up of V3O8 layers with interstitial Ba2+ ions and water molecules. Its striking feature is that the V3O8 layers are bridged imperfectly by partially absent VO5 trigonal bipyramids which form tunnel-like openings. The structure is thus regarded as an intermediate between layered and tunnel structure types. Interstitial Ba2+ ions were observed to be displaced from the position on the mirror plane. (C) 1995 Academic Press, Inc.