Phase equilibria in Tl2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Fe, Cr, Al) system and the crystal structure of triple molybdate Tl(FeHf0.5)(MoO4)3

Tl2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Fe, Cr, Al) system was studied in the subsolidus area by X-ray powder diffraction. Tl(FeHf0.5)(MoO4)3 monocrystals were grown from melt solutions with spontaneous nucleation. Their crystal structure was refined from X-ray diffraction data (Bruker X8 Apex automated diffractometer, MoKαradiation). The trigonal unit cell parameters are a = b = 13.0324(2) Å, c = 11.8083(3) Å, V = 1736.87(6) Å3, Z = 6, sp. gr. R 3. The three-dimensional mixed framework of structure is formed by Mo-tetrahedrons, united through the general O-tops with octahedrons (Fe, Hf) O6. Atoms of thallium are located in wide channels of the framework.