Practical Electron Microscopy and Database

Figure 2329a (a) shows the structural model of a niobium tungsten oxide (Nb₈W₉O₄₇, orthorhombic, P2₁2₁2, a = 1.224 nm; b = 3.658 nm; and c = 0.394 nm)† in projection onto the ab-plane. The filled circles represent the pentagonal tunnels occupied by M-O (M = Nb or W) strings. Figure 2329a (b) shows a HRTEM image of another niobium tungsten oxide (Nb₄W₁₃O₄₇) along [001]. The inset shows a highlighted representation of the structure: the positions of octahedrally coordinated cation sites are connected by lines, while the the pentagonal tunnels occupied by cations (Nb or W) are indicated by open circles. The two distinct orientations of the TTB unit (white lines) and a unit cell (black rectangle) are outlined.

Figure 2329a. (a) The structural model of Nb₈W₉O₄₇ in projection onto the
ab-plane and (b) a HRTEM image of Nb₄W₁₃O₄₇ along [001]. [1]

[1] M.J. Sayagués, F. Krumeich, J.L. Hutchison, Solid-gas reactions of complex oxides inside an environmental high-resolution transmission electron microscope, Micron 32 (2001) 457 - 471.