A Titanium and Tantalum Phosphate LiNaTiTa2 P2 O13 with An Open Framework hosting Li and Na Ions.

Herein, we report a detailed structural, electric, thermal and optical analysis of a titanium and tantalum phosphate LiNaTiTa2 P2 O13 . The title compound is comprised of typical ReO3 -type layers constituted by corner-sharing TiO6 and TaO6 octahedra, bridged by PO4 tetrahedra, and the structure is closely related to monophosphate niobium bronzes. The existence of pentagonal tunnels, hosting the Li+ and Na+ ions, endows LiNaTiTa2 P2 O13 a moderate ion transportation behavior (4.67×10-4  S/cm at 823 K). In addition, the successful substitution of Nb for Ta in LiNaTiTa2 P2 O13 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.