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)3V2O3(VO)(PO4)2(HPO4)

Author： Schindler M. Joswig W. Baur W.H.

Publisher： Academic Press

ISSN： 0022-4596

Source： Journal of Solid State Chemistry, Vol.134, Iss.2, 1997-12, pp. : 286-293

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Abstract

An examination of the NH4/VO5/P/H2O system at 473 K under hydrothermal conditions yielded the (NH4)3V2O3(VO)(PO4)2(HPO4) and NH4VOPO4 phases. The crystal structure of the first compound is isotypical with the corresponding Tl+ and K+ phases. The cations NH+4 and Tl+ have similar coordinations against oxygen. The investigation of the crystal structure of the second compound (space group Pn2n) shows it to be related to other ABOTO4 phases of the potassium titanyl phosphate type with A=Na+, Ag+, NH+4, 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⋅1.5H2O, KVOPO4, and K-FVP-1 (Frankfurt vanadium phosphate, one, or for short, FVP-1). The microporous K-FVP-1 compound was synthesized in a similar 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) A. Copyright 1997 Academic Press.