SCHEDULED MAINTENANCE:
Electron microscopy of the niobium oxides. Part II. Multiple phases in the system Nb2O5+ MgF2
Abstract
The formation of mixed phases in the system MgF2+ Nb2O5 has been examined, on the grounds that similarity in ionic radii between Mg and Ti, and between F and O, should lead to the analogues of the known titanium–niobium block structure oxides. Electron diffraction and direct electron microscope lattice imaging methods show that, in addition to the compound already described as MgNb14O35F2, with the (5 × 3)∞ structure, phases iso-structural with H-Nb2O5, N-Nb2O5, TiNb24O62, and Ti2Nb10O29 are formed. By compensatory substitution, each of these structures represents a solid solution series and mixtures with compositions on the MgF2–Nb2O5 tie line yield multiphase products. Regular intergrowth structures may be formed between the basic structural types.
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