Synthesis, structure and characterisation of Fe0.50Ti2(PO4)3: A new material with Nasicon-like structure

A new iron titanyl phosphate Fe0.50Ti2(PO4)3 was synthesized by both solid-state reaction and Cu2+–Fe2+ ion exchange method. The material was then characterized by X-ray diffraction, Mössbauer, magnetic susceptibility measurements and optical absorption. The crystal structure of the compound was refined, using X-ray powder diffraction data, by the Rietveld profile method; it crystallizes in the rhombohedral system, space group R3¯, with a=8.511(1) Å and c=20.985(3) Å, V=1316.45(3) Å3 and Z=6. The structure, which is compared to that of Mn0.50Ti2(PO4)3 is built up from [TiO6] octahedra and [PO4] tetrahedra which are linked by corner sharing along the c-axis. Fe2+ cations are located in half of the antiprism MI sites and are orderly distributed with vacancies within the two possible positions of the MI sites of R3¯. These results were supported by the Mössbauer studies that showed the presence of one Fe2+ site in the high spin state (t2g4eg2). The Curie–Weiss-type behavior is observed in the magnetic susceptibility. Diffuse reflectance spectrum indicates the presence of octahedrally coordinated Fe2+ ions.

Polyhedral view down [110] of the Fe0.50Ti2(PO4)3 structure ([TiO6] octahedra are shown with light shading, [PO4] tetrahedra with dark shading, Fe/□ as circles).Figure optionsDownload as PowerPoint slide