Determination of formation regions of titanium phosphates; determination of the crystal structure of beta-titanium phosphate, Ti(PO4)(H2PO4), from neutron powder data

摘要

The formation region of the various types of layered titanium hydrogen phosphate hydrates was investigated. The materials were prepared by hydrothermal methods, treating amorphous titanium phosphate with phosphoric acid (8 to 16 M) in the temperature range 175 to 250 degrees C, The materials obtained were: alpha-Ti(HPO4)(2) . H2O, gamma-Ti(PO4)(H2PO4) . 2H(2)O, and its anhydrous form beta-Ti(PO4)(H2PO4). The structure of beta-Ti(PO4) (H2PO4) has been determined by Rietveld powder refinement of high resolution neutron diffraction data. The structure is refined in the monoclinic space group P2(1) (No. 14). The unit cell parameters are: a = 18.9503(4) Angstrom, b = 6.3127(1) Angstrom, c = 5.1391(1) Angstrom, beta = 105.366(2)degrees; Z = 4. The final agreement factors were: R-p = 2.9% and R-wp = 3.8%. The structure of beta-Ti(PO4)(H2PO4) is built from TiO6 octahedra linked together by tertiary phosphate (PO4) and dihydrogen phosphate ((OH)(2)PO2) tetrahedra. The layers are held together by hydrogen bonds. (C) 1998 Academic Press. [References: 19]