Spectroscopic and thermal contribution to the structural characterization of vandenbrandeite

Abstract

The vibrational (IR and Raman) spectrum of Vandenbrandeite, Cu[UO₂(OH)₄], has been recorded and discussed on the basis of structural considerations through the use of empirical expressions. As the H-bonding in the lattice is poorly known, the characteristics of this bond has been analyzed with the aid of H/D isotope exchange, thermal assays and electron microscopy. Samples are practically amorphous to XRD up to ∼700°C whereas crystals morphologically different by SEM microscopy and well characterized by XRD technique are observed from ∼800°C. Vibrational spectroscopy reveals that the atomic arrangement in the structure remains largely unaffected as the dehydration proceeds, suggesting a topochemically controlled process. EPR spectroscopy suggests a disordered distribution of Cu(II) ions as temperature increases. Finally, thermal dehydroxylation and paragenesis of the copper-uranyl oxide hydrate are correlated.