On the new oxovanadium phosphate NaZnVOPO4(HPO4) obtained at 510 K from hydrothermal treatment

Pale blue powders of NaZnVOPO4(HPO4) were prepared in quantitative yield from hydrothermal treatments. The structure of NaZnVOPO4(HPO4) was solved from single crystal X-ray diffraction data in the centrosymmetric monoclinic space group P21/c (no. 14), a = 8.5441(2) Å, b = 8.9831(2) Å, c = 9.0836(2) Å, β = 91.241(1)°, Z = 4 (R1(Fo) = 0.026, wR2(Fo2) = 0.068). The structure results from the hetero-condensation of distorted octahedra VO6 with tetrahedra HxPO4 and ZnO4 by sharing apices and edges. The remaining voids of the 3D framework [ZnVOPO4(HPO4)]− located in tunnels that run along [011] are occupied by sodium ions. The title compound dehydrates at T ∼ 770 K with an overall weight loss of ∼2.3% consistent with the structural results. The crystal chemical relationships with Na3VOPO4(HPO4) and the high-temperature phase SrZnVO(PO4)2 are discussed.