SYNTHESIS AND CRYSTAL-STRUCTURES OF ALPHA-CSTI3P5O19 AND BETA-CSTI3P5O19

Crystals of alpha-CsTi3P5O19, the low temperature phase, and beta-CsTi 3P5O19, the high temperature phase, have been obtained by flux growth methods and structurally characterized by single crystal X-ray diffrac tion techniques. Crystal data: alpha-CsTi3P5O19, monoclinic, Cm, a = 9 .309(2) Angstrom, b = 14.081(3) Angstrom, c = 6.314(1) Angstrom, beta = 105.82(3)degrees, V = 796.3 Angstrom(3), Z = 2, R = 0.027 for 928 un ique reflections; beta-CsTi3P5O19, monoclinic, C2/c, a = 10.987(1) Ang strom, b = 16.588(1) Angstrom, c = 8.7618(8) Angstrom, beta = 100.09(1 )degrees, V = 1572.2 Angstrom(3), Z = 4, R = 0.038 for 1678 unique ref lections. The two polymorphs have different three-dimensional networks of vertex-sharing octahedra and tetrahedra. The framework of the alph a-phase consists of dimers of corner-sharing TiO6 octahedra and discre te TiO6 octahedra joined through PO4 tetrahedra and P2O7 groups by cor ner-sharing. The beta-phase is built up from discrete TiO6 octahedra, PO4 tetrahedra, and P2O7 groups. The structural formulas are CsTi(Ti2O )(PO4)(P2O7)(2) and CsTi3(PO4)(3)(P2O7) for the alpha- and beta-phases , respectively. Both frameworks have tunnels where the cesium cations are located. The cesium cations in the beta-phase are disordered. (C) 1995 Academic Press, Inc.