Tl 2MoO 4-Ho 2(MoO 4)3-Zr(MoO 4)2 system and crystal line structure of double molybdate Ho 2Zr 2(MoO 4) 7

The Tl 2MoO 4-Ho 2(MoO 4) 3-Zr(MoO 4) 2 system was studied in the subsolidus region using X-ray powder diffraction. New triple molybdates were found to exist in this system: Tl 5HoZr(MoO 4) 6 (5:1:2), and Tl 2HoZr 2(MoO 4) 65 (2:1:4). The first Ho 2Zr 2(MoO 4) 7 single crystals were grown from melt solutions with spontaneous nucleation. Their crystal struc Ture was refined from X-ray diffraction data (Bruker X8 Apex automated diffractometer, MoK a radiation, 5411 F(hkl), R=0.0182). The monoclinic unit cell parameters are as follows: a=20.6668(4), b=9.8193(2), c=13.8187(3) A, 3=113.678(1) о, V=2568.20(9) A 3, Z=4, p calcd=4.221 g/cm 3, space group C2/c. The openwork three-dimensional skeleton of structure is made of ZrO 6-octahedrons, HoOg-tetragonal antiprisms with the tops of 4 grades МоО 4-tetrahedra attached to them.