Synthesis, crystal structure, cationic mobility, thermal evolution and spectroscopic study of Cs8(UO2)4(WO4)4(WO5)2 containing infinite uranyl tungstate chains
Résumé
In this structure, the uranium atoms adopt UO7 pentagonal bipyramid coordination, while tungsten atoms are in two different environments, WO4 tetrahedral and WO5 square pyramidal coordinations. The association of uranyl ions (UO7) and tungstate oxoanions WO4 and WO5, gives infinite chains 1∞[(UO2)4(WO4)4(WO5)2]8- parallel to [100]. These types of chains has not been previously observed. The association of these chains in the (010) plane gives undulated pseudo-layers stacked along [010]. The cohesion between the chains is assured by alkaline Cs+ cations. The conductivity measurements, between 200 and 600 °C, show an Arrhenius law evolution. Infrared spectroscopy investigated at room temperature in the 400–4000 cm−1 wave number range, has allowed the identification of the various modes of vibrations of uranyl and tungstate polyhedrons.