CsUV3O11, a New Uranyl Vanadate with a Layered Structure

Abstract

A new cesium uranyl vanadate CsUV3O11 has been synthesized by solid state reaction. Its crystal structure has been determined from single-crystal X-ray diffraction data. It crystallizes in the monoclinic system with space group P21/a and unit cell parameters a=11.904(2) Å, b=6.8321(6) Å, c= 12.095(2) Å, β=106.989(5)°, Z=4, and Dexp=4.89(2) g/cm3. A full-matrix least squares refinement yielded R=0.046 and Rw=0.045 for 1831 independent reflections with I>3σ(I) collected on a Nonius CAD4 diffractometer (MoKα radiation). The structure of CsUV3O11 is characterized by [UV3O11]∞ layers parallel to the (001) plane. The layers, very similar to those found in UV3O10, are built up from VO5 square pyramids sharing corners of their equatorial bases and UO8 hexagonal bipyramids, the U atoms occupying the hexagonal holes created by the VO5 array. The Cs+ ions are located between two successive layers and hold them together; the Cs+ ions and two layers constitute a neutral “sandwich” {(UV3O−11)–(Cs)2+2–(UV3O−11)}. In this unusual structure, the neutral sandwiches are stacked one above another along the [104] direction with no formal chemical bonds between the neutral sandwiches. The Cs mobilities in CsUV3O11 and Cs carnotite are compared.