A novel intergrowth structure between ReO₃-type and tetragonal tungsten bronze-type in the Zr/Nb/W/O system

The intergrowth structure of a zirconium niobium tungsten oxide has been determined by transmission electron microscopy methods. Electron diffraction patterns reveal the parameters of the monoclinic lattice: a = 19.0, b = 3.9 and c = 13.8 Å; β = 93.5°. Additional reflections in higher-order Laue zones indicate the presence of a diagonal glide plane, leading to a larger unit cell. A structure model of composition Zr_nNb_8−2nW_12+nO₅₆ (0.5 < n < 1) has been derived from high-resolution lattice images. Alternating slabs of ReO₃-type and of tetragonal tungsten bronze structure are intergrown coherently. Two five-membered rings of MO₆ octahedra belonging to adjacent tetragonal tungsten bronze subcells are connected by having two octahedra in common. For the first time, this arrangement of double pentagons is observed in a regular structure.

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