Structural and vibrational study of titanium Monophosphates Na0.5M0.25Ti2 (PO4)3 (M = Mn, Ni)

Abstract

<jats:p>This work is a systematic study of titanium phosphates compounds Na0.5M0.25Ti2(PO4)3 (M = Mn, Ni), which are characterized by X-ray diffraction (XRD), IR spectrometry, Raman and scanning electron microscopy. Indeed, the crystalline structures of the two compounds were determined in the orthorhombic system, with space group Pmmm (Z = 4); the determined unit cell parameters are: a = 14.59Å, b = 13.31 Å, c = 2.6 Å for Na0.5Mn0.25Ti2(PO4)3, and a = 14.60 Å, b = 13.31 Å, c = 2.67Å for Na0.5Ni0.25Ti2(PO4)3. The structures, compared to that of Li0.5M0.25Ti2(PO4)3, are constructed from [TiO6] octahedra and [PO4] tetrahedra connected by sharing angles along the c axis. The cations M = Mn2+, Ni2+, are located in half of the antiprismatic infection sites and are ordered.</jats:p>