The effect of metamictization on the Raman spectroscopy of the uranyl titanate mineral davidite (La,Ce)(Y,U,Fe2+)(Ti,Fe3+)20(O,OH)38

Abstract

Raman spectra of the uranyl titanate mineral davidite-(La), (La,Ce)(Y,U,Fe2+)(Ti,Fe3+)20(O,OH)38, were analyzed and related to the mineral structure. Observed bands are attributed to the TiO and (UO2)2+ stretching and bending vibrations, U–OH bending vibrations, H2O and (OH)− stretching, bending and libration modes. U–O bond lengths in uranyls and O-H ··· O bond lengths are calculated from the wavenumbers assigned to the stretching vibrations. Raman bands of davidite-(La) are in harmony with those of the uranyl oxyhydroxides. The mineral davidite-(La) is metamict, as is evidenced by the intensity of the UO stretching and bending modes being of lower intensity than expected and with bands that are significantly broader.