Infrared and X-ray diffraction spectra of ammonium uranyl carbonate

Ammonium uranyl carbonate was precipitated at various temperatures (50-65 C), flow rates of CO2 (25-40 l h-1) and NH3 (35-65 l h-1) and precipitation times (160-320 min). In the X-ray diffraction patterns, all products exhibited the diffraction lines characteristic of (NH4)2UO2(CO3)3, with small differences in intensity. The IR spectra (4000-200 cm-1) of the fresh samples as well as of the stored solid showed exactly the same patterns. They exhibited the characteristic vibrations of (NH4)+ at 3230 cm-1 (ν3) and at 1445 cm-1 (ν4) and of (CO3)2-at 1520, 1050, 720 and 690 cm-1. The uranyl ion antisymmetric stretching (ν3) vibrations appeared at 890 cm-1. The bending and stretching modes of (UO2)2+ are greatly hindered, owing to hexagonal coordination with the three bidentate carbonate groups. (orig.)