Structure of an L-Ta2O5-type phase in the L-Ta2O5–TiO2 system

Abstract

The structure of an L-Ta₂O₅-type phase in the system L-Ta₂O₅–TiO₂ has been derived with the help of high-resolution electron micrographs and electron–diffraction patterns. It is described as an ordered intergrowth of α-U₃O₈ and β-U₃O₈ structure types. The parameters of the ‘shift-lattice’ formalism, previously used to account for the diffraction patterns of these phases, are related to the structure proposed. Electron micrographs also suggest that the structure may contain interstitial metal atoms. The idealised structure, which consists of folded chains of β-U₃O₈-type pentagonal bipyramids in the sequence 6, 8, 6, 8, is also described. The relevance of the structure to other members of the L-Ta₂O₅ series is discussed.