Ag1.2V3O8 crystal structure:: Relationship with Ag2V4O11-y interpretation of physical properties

It is demonstrated that the Ag1+xV3O8 phase can derive from a sprouting phenomenon easily occurring in the Ag2V4O11 vanadate. The oxygen departure rough formula Ag2V4O11-y drives to the formation of the title phase for y = 0.16. Single crystals were obtained and fully characterized by X-ray single-crystal techniques. Ag1.2V3O8 crystallizes in the monoclinic system, space group P2(1)/m, a 7.382(5) Angstrom, b = 3.6029(6) Angstrom, c = 12.193(8) Angstrom, beta = 107.39(6)degrees, Z = 2, and is isostructural with Li1+xV3O8. Structural relationships with Ag2V4O11-y are detailed. It is shown that silver atoms, located between the [V3O8](n) layers formed by association of two octahedra and a trigonal bipyramid by edge and corner sharing, occupy two crystallographic sites. Electron density computations show that silver atoms move along the [010] direction, explaining the interesting electrochemical properties. Magnetic measurements establish the perfect correspondence between inserted Ag+ ions and the V4+ yield, giving the formula Ag1+yV3-y5+Vy4+O8. (C) 1997 Academic Press.