CRYSTAL STRUCTURE OF BINARY MOLYBDATE Pr<sub>2</sub>Hf<sub>3</sub>(MoO<sub>4</sub>)<sub>9 </sub>
Crystals of binary praseodymium and hafnium molybdate of Pr2Hf3(MoO4)9 composition are grown by solution-melt crystallization under spontaneous nucleation conditions. By the X-ray diffraction data (X8 Apex automated diffractometer, МоKα radiation, 2262 F(hkl), R = 0.0170) its composition and crystal structure are determined. Parameters of the trigonal unit cell are: a = b = 9.8001(1) Å, c = 58.7095(8) Å, V = 4883.15(10) Å3, Z = 6, space group Rc. The crystal structure is composed of three types of polyhedra: МоО4 tetrahedra, HfO6 octahedra, and nine-vertex PrO9. All three types of polyhedra are bonded among themselves by common oxygen vertices of bridging МоО4 tetrahedra forming an openwork three-dimensional structure.