Structure of UMo4O14 oxide

Abstract

The structure and composition of UMo4O14 synthesized by solid state reaction method have been investigated by High Resolution Transmission Electron Microscopy (HRTEM), High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM), Selected Area Electron Diffraction SAED, and energy Dispersive X-ray microanalysis (EDX). The unit cell is orthorhombic, Cccm (66), a = 0.732, b = 3.247, c = 0.81, α = 90.0, β = 90.0, γ = 90.0. It comprises 2 layers of U and Mo cations. Each following layer is shifted relatively to the previous one by vector a/2. The infinite layers of composition Mo2O7 running perpendicular to b direction can be easily distinguished in the image. These double MoO3 octahedra wide slabs are typical for U–Mo oxides. They are linked to each other by another MoO3 octahedra and infinite one octahedral wide slab, forming a two rows of hexagonal coordinated bi-pyramids occupied by …U–O–Mo–O… strings. One of characteristic features of the UMo4O14 phase is the incommensurate modulation observed in some crystals. The goal of this paper is to reveal three-dimensional atomic structure of U–Mo oxide and to clarify in what way it depends on U/Mo composition.