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, Mossbauer, magnetic susceptibility measurements and optical absorption. The crystal structure of the compound was refined, using X-ray powder diffraction data, by the Rielveld profile method; it crystallizes in the rhombohedral system, space group R, with a = 8.51 l(l)angstrom and c = 20.985(3)A V = 1316.45(3) angstrom(3) 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 M-1 sites and are orderly distributed with vacancies within the two possible positions of the M-1 sites of R (3) over bar. These results were supported by the Mossbauer studies that showed the presence of one Fe2+ site in the high spin state (t(2g)(4)e(g)(2)). The Curie-Weiss-type behavior is observed in the magnetic susceptibility. Diffuse reflectance spectrum indicates the presence of octahedrally coordinated Fe2+ ions. (c) 2007 Elsevier Inc. All rights reserved.