Preparation, crystal structure, and luminescence of magnesium molybdate and tungstate monohydrates, MgMoO 4 · H 2O and MgWO 4 · H 2O

Abstract

Triclinic MgMoO 4 · H 2O and the isomorphous MgWO 4 · H 2O have been prepared under mild hydrothermal conditions in single crystalline form and the crystal structure of MgMoO 4 · H 2O has been determined by X-ray diffraction. The structure is compared to a model deduced earlier for MgWO 4 · H 2O from topotaxy data, with which the general topology agrees, but there is an important difference in the orientation of MoO 4-tetrahedra. The X-ray powder diffraction data, thermal dehydration behavior, as well as the luminescence properties are reported and the latter compared with data of related phases. Crystal data are: Triclinic, space group P −1; MgMoO 4 · H 2O: a = 5.665, Å, b = 5.869, Å, c = 6.875, Å, α = 100.80°, β = 95.05°, γ = 106.57°; MgWO 4 · H 2O: a = 5.681, Å, b = 5.887, Å, c = 6.870, Å, α = 100.85°, β = 95.44°, γ = 106.55°.