Synthesis, structure, magnetic susceptibility and Mössbauer and Raman spectroscopies of the new oxyphosphate Fe0.50TiO(PO4)

A new iron titanyl oxyphosphate Fe0.50TiO(PO4) was synthesized by both solid-state reaction and Cu2+–Fe2+ ion exchange method. The material was then characterized by X-ray diffraction, Mössbauer spectroscopy, magnetic susceptibility measurements and Raman spectroscopy. The crystal structure of the compound was refined, using X-ray powder diffraction data, by Rietveld profile method; it crytallizes in the monoclinic system, space group P21/c (No.14), with a=7.4039 (3) Å, b=7.3838 (3) Å, c=7.4083 (3) Å, B=120.36° (1); V=349.44 (2) Å 3 and Z=4. The volume of the title compound is comparable to those of the M0.50IITiO(PO4) series, where MII=Mg, Co, Ni and Zn. The framework is built up from [TiO6] octahedra and [PO4] tetrahedra. [TiO6] octahedra are linked together by corners and form infinite chains along the c-axis. Ti atoms are displaced from the center of octahedral units showing an alternating short distance (1.73 Å) and a long one (2.22 Å). These chains are linked together by [PO4] tetrahedra. Fe2+ cations occupy a triangle-based antiprism sharing two faces with two [TiO6] octahedra. Mössbauer and magnetic measurements show the existence of iron only in divalent state, located exclusively in octahedral sites with high spin configuration (t2g4eg2). Raman study confirms the existence of Ti–O–Ti chains