Abstract
A new nonstoichiometric titanophosphate, K 2− x Ti 2(PO 4) 3, has been isolated for 0 ≤ x ≤ 0.5. This compound which belongs to the Langbeinite structure is characterized by a mixed valence of titanium Ti III Ti IV . The structures of two compositions x = 0 and x = 0.25 have been determined from a single-crystal X-ray diffraction study. This cubic phase ( a = 9.8559 Å for x = 0.25, a = 9.8688 Å for x = 0; space group P2 13) is compared to Nasicon Na x Ti 2(PO 4) 3. The evolution of the TiO distances and calculations of the mean oxidation state of titanium allow a distribution of the Ti III and Ti IV ions on the two types of site to be proposed. The possibility of extending this structure to other univalent cations has been demonstrated with the synthesis of the isotypic compounds Rb 2Ti 2(PO 4) 3 and Tl 2Ti 2(PO 4) 3.
Published Version
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