A Titanium and Tantalum Phosphate LiNaTiTa2P2O13 with An Open Framework hosting Li and Na Ions

Graphical LiNaTiTa 2 P 2 O 13 displays an open framework comprised of staggered [Ti 1/3 Ta 2/3 O 3 ] ∞ layers and PO 4 tetrahedra with a herringbone-like stacking pattern, similar to monophosphate niobium bronzes. The existence of pentagonal tunnels, hosting the Li + and Na + ions, endow LiNaTiTa 2 P 2 O 13 a moderate ion transport capability (4.67×10 −4 S/cm at 823 K). In addition, the layers constituted by corner-sharing TiO6 and TaO6 octahedra endow a possibility as being photo-catalyst. The successful substitution of Nb for Ta results in the optical absorption red-shifted towards visible range with a narrowing band gap comparable to that of TiO 2 (3.2 eV). Herein, we report a detailed structural, electric, thermal and optical analysis of a titanium and tantalum phosphate LiNaTiTa 2 P 2 O 13 . The title compound is comprised of typical ReO 3 -type layers constituted by corner-sharing TiO 6 and TaO 6 octahedra, bridged by PO 4 tetrahedra, and the structure is closely related to monophosphate niobium bronzes. The existence of pentagonal tunnels, hosting the Li + and Na + ions, endows LiNaTiTa 2 P 2 O 13 a moderate ion transportation behavior (4.67×10 −4 S/cm at 823 K). In addition, the successful substitution of Nb for Ta in LiNaTiTa 2 P 2 O 13 results in the optical absorption red-shift towards visible range with a narrowing band gap, which may provide a route of isomorphic replacement to band engineering for photo-catalysis.