Synthesis and structural study of phosphates K2Mg0.5Zr1.5(PO4)(3,) Rb(2)Mg(0.)5Zr(1.)5(PO4)(3), and Cs2Mg0.5Zr1.5(PO4)(3) with langbeinite structure

摘要

New orthophosphates K2Mg0.5Zr1.5(PO4)(3), Rb2Mg0.5Zr1.5(PO4)(3), and Cs2Mg0.5Zr1.5(PO4)(3) are synthesized and characterized by X-ray powder diffraction and IR spectroscopy. These orthophosphates crystallize in the structure type of the mineral langbeinite (cubic system, sp. gr. P2(1)3, Z = 4). The structure of phosphate Cs2Mg0.5Zr1.5(PO4)(3) is refined by the Rietveld method using neutron powder diffraction data (a DN-2 time-of-flight diffractometer, the Joint Institute for Nuclear Research, Dubna, Russia) in the temperature range 15-600 degrees C. The structure of this compound is characterized by the mixed [Mg0.5Zr1.5(PO4)(3)](2-) framework, whose large cavities are occupied by cesium atoms. Mg2+ and Zr4+ cations randomly occupy two crystal] ographically independent positions. The influence of the temperature factor on distortions of the framework polyhedra is analyzed. (C) 2005 Pleiades Publishing, Inc.