0000000000732717
AUTHOR
A. Le Bail
Synthesis and crystal structure of α-NH4(VO2)(HPO4)
Abstract Hydrothermal synthesis starting from β-NH 4 (VO 2 )(HPO 4 ) leads to α-NH 4 (VO 2 )(HPO 4 ): orthorhombic, space group Pb 2 1 a ; Z = 4; a = 6.830(1) A, b = 9.233(2) A, c = 8.817(2) A; R = 0.037 for 3371 reflections. NH + 4 cations connect isolated chains of trans -corner sharing VO 5 square pyramids running along the a -axis. The a -phase transforms irreversibly into the β-form by heating near 200°C. Comparison is made between the two phases.
Synthesis and crystal structure of Na1+xV4P4O17(OH) (x ≈ 1.44)
Abstract Hydrothermal synthesis starting from Na0.46VOPO4 · 1.58H2O leads to a new mixed-valence sodium vanadium phosphate: Na2.44V4P4O17(OH) (orthorhombic, space group Pnma; Z = 4; a = 13.723(5) A, b = 6.314(2) A, c = 16.139(4) A; R = 0.032 for 2659 reflections). In this phase, the interconnection of three complex types of infinite chains, built from VO6 octahedra and PO4 tetrahedra, sometimes edgeshared, defines tunnels partly occupied by a portion of the sodium atoms.