| Abstract: | Contributions to the Investigation of Inorganic Non-stoichiometric Compounds. XXII. New Metastable Block Structures in the System Nb2O5/WO3, Electron Optical Investigation We succeeded in considerably expanding the region of existence of block structures. By substituting W for Nb, while the ratio O/∑M (M ? Nb, W) is kept constant, and starting from the known phases Nb2O5: WO3 = 6:1, 7:3, 8:5 and 9:8 one obtains series of solid solutions whose metastable products of oxidation have block structures too. In contrast to the solid solutions which have the structures of the starting phases i. e. with socalled blocks of [3 × 4], [4 × 4], [4 × 5] and [5 × 5] M? O-octahedra, the products of the oxidation have structures in which some edge sharing octahedra changed their connections to become octahedra sharing corners thus opening up the possibility for the formation of blocks with twice the number of octahedra as before. Rows of these large blocks with e. g. [4 × 6] or [4 × 8] octahedra alternate nonperiodically with rows of smaller blocks of the initial size. Details of these heavily disordered structures could only be discerned with the help of high resolution electron microscopy. |
