THE HYDROTHERMAL NH4 V/P/H2O AND K/V/P/N(C2H5)(3)/H2O SYSTEMS AT 473 K AND THE CRYSTAL-STRUCTURES OF NH4VOPO4 AND (NH4)(3)V2O3(VO)(PO4)(2)(HPO4)/

An examination of the NH4/VO5/P/H2O system at 473 K under hydrothermal conditions yielded the (NH4)(3)V2O3(VO) (PO4)(2)(HPO4) and NH4VOPO4 p hases. The crystal structure of the first compound is isotypical with the corresponding Tl+ and K+ phases. The cations NH4+ and Tl+ have sim ilar coordinations against oxygen. The investigation of the crystal st ructure of the second compound (space group Pn2n) shows it to be relat ed to other ABOTO(4) phases of the potassium titanyl phosphate type wi th A = Na+, Ag+, NH4+, Rb+, K+, and Tl+, and B = Ti4+, V4+, Sn4+, Fe4, Ge4+, Ga3+, Zr4+, Sb5+, and Nb5+, and T = P5+, Ge4+, Si4+, and As5+, but none of them crystallize in space group Pn2n. In the K/V/P/N(C2H5 )(3)/H2O system, three different K phases were found: K0.5VOPO4 . 1.5H (2)O, KVOPO4, and K-FVP-1 (frankfurt vanadium phosphate, one, or for s hort, FVP-1). The microporous K-FVP-1 compound was synthesized in a si milar pH range as the isotypic Na-FVP-1 phase. The V4+/V5+ ratio of K- FVP-1 varies from 3.5(1)/1.5(1) to 1.6(1)/3.4(1) and the corresponding lattice constants range from 16.0013(6) to 15.7665(4) Angstrom. (C) 1 997 Academic Press.