Synthesis and characterization of francoisite-(Nd): Nd[(UO2)3O(OH)(PO4)2]•6H2O

In this report, synthesis and characterization data for francoisite-(Nd), Nd[UO2)(3)O(OH) (PO4)(2)]center dot 6H(2)O are presented. Experimental studies including chemical digestion, thermogravimetric analysis (TG), attenuated total reflection infrared spectroscopy (ATR-IR), Raman spectroscopy, and X-ray powder diffraction (XRD) were conducted. The local bonding environments of uranyl and water were investigated with ATR-IR and Raman spectroscopy. The average axial uranium-oxygen bond lengths [R(U=0)] and the oxygen-oxygen hydrogen bond distances [R(O center dot center dot center dot O)] in water were calculated from the vibrational frequencies of the stretching modes of uranyl and water, respectively. The IR spectra of protiated and deuterated francoisite-(Nd) appear to confirm a coordinated hydroxyl group bridging vicinal uranyl groups in the structural unit. These studies provide the basis for further thermodynamic (e.g., calorimetry, solubility, and sorption) and geochemical modeling investigations of hydrated uranyl phosphate compounds.