Rietveld refinements of the solid solution Li(1-2x)NixTiO(PO4) (0 ≤ x ≤ 0.50)

Li(1-2x)NixTiO(PO4) oxyphosphates with 0 less than or equal to x less than or equal to 0.10 crystallize in the orthorhombic system with the space group Pnma, those with 0.10 < x less than or equal to 0.25 crystallize in the monoclinic system with the space group P2(1)/c and compositions with 0.25 < x < 0.50 present a mixture of the limit of the solid solution Li0.50M0.25TiO(PO4) and Ni0.50TiO(PO4). The structure of the compositions 0 less than or equal to x less than or equal to 0.25 is based on a three-dimensional anionic framework constructed of chains of alternating TiO6 octahedra and PO4 tetrahedra, with the lithium and nickel atoms in the cavities in the framework. The dominant structural units in the compositions are chains of tilted corner-sharing TiO6 octahedra running parallel to one of the axis. The oxygen atoms of the shared corners, not implied in (PO4) tetrahedra, justify the oxyphosphate designation. Titanium atoms are displaced from the geometrical center of the octahedra resulting in alternating long (approximate to2.25 Angstrom) and short (approximate to1.71 Angstrom) Ti-O(1) bonds. The four remaining Ti-O bond distances have intermediate values ranging from 1.91 to 2.06 Angstrom. (C) 2004 Elsevier Ltd. All rights reserved.