[Bi12O14E12](n) columns and lone pairs E in Bi13Mo4VO34E13: Synthesis, crystal structure, and chemistry of the Bi2O3-MoO3-V2O5 system

A new phase, Bi13Mo4VO34E13 (E: Bi(III) lone pair) was found in the Bi2O3-MoO3-V2O5 system and its formula determined via single crystal analysis and confirmed by solid state synthesis. It crystallizes in the monoclinic system, space group P2/c, with cell parameters a = 11.652(7) Angstrom, b = 5.7923(8) Angstrom, c = 24.420(9) Angstrom, beta = 101.38(6)degrees, and Z = 2. The crystal structure is built up by infinite [Bi12O14E12](n) columns surrounded by 10 (Mo, V)O-4 tetrahedra, situated on layers parallel to (100) and (001), with an extra Bi atom located at the intersection of these ''(Mo, V)O-4 layers'' in between two tetrahedra. The Bi13Mo4VO34E13 structure is in general agreement with that of R. N. Vannier et al. (1996, J. Solid State Chem. 111, 118) giving a structural formulation Bi26M10O68 but with their chemical formulations giving Bi26Mo10O69 or Bi26Mo6V4O67 and hypothetical nonstoichiometry Bi26M10O3. Taking into account the cell dimensions and structural details of Bi13Mo4VO34E13, which show that a reported phase like Bi6Mo2O15 could also be isostructural, a nem hypothesis based on the possible replacement of BiO4E trigonal bipyramid and/or BiO3E tetrahedra for MoO4 tetrahedra strengthens the probability that there is a continuous solid solution in the Bi2O3-MoO3 system between the compositions 1.43 Bi2O3: 1 MoO3 and 1.75 Bi2O3: 1 MoO3. Synthesis and cell dimensions of various compositions supporting these ideas are given. The domain of existence for such phases can extend in the pseudo-ternary Bi2O3-MoO3-V2O5 system up to the phase Bi13Mo4VO34; this triangular area excludes Bi26Mo10O69 and Bi26Mo6V4O67 compositions. (C) 1997 Academic Press.