A series of aluminum tungsten oxides crystallizing in a new ReO3-related structure type

A series of new aluminum tungsten oxides with the general formula Al4W2nO6n+2 (n=4–7) was found and structurally characterized by electron diffraction, high-resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The structural model for Al4W10O32 (I4/mmm (space group no. 139); a≈0.375, c≈3.95 nm) consists of slabs of [5×∞×∞] corner-sharing WO6 octahedra that are connected via edge-sharing to AlO6 octahedra. Simulated HRTEM images agree well with the experimental ones and thus support the proposed structural model. The connection between adjacent slabs of WO3 via AlO6 octahedra represents a novel variant of crystallographic shear operation for ReO3-type structures. The crystallites display a wide range of stacking sequences that are frequently intergrown with each other.