Original paper

Molecular structure of the uranyl mineral zippeite - An XRD, SEM and Raman spectroscopic study

Frost, Ray L.; Weier, Matt L.; Bostrom, Thor; Čejka, Jiří Martens


Raman spectra at 298 and 77 K and infrared spectra of the uranyl sulfate mineral zippeite, K2[(UO2)6(SO4)3O(OH)6 ] · 4H2O, were studied. Observed bands were tentatively attributed to the (UO2)2+ and (SO4)2- stretching and bending vibrations, the OH stretching vibrations of water molecules and hydroxyls, H2O bending vibrations and libration modes, and δ U–OH bending vibrations. Empirical relations were used for calculation of U–O bond lengths in uranyl R = f(ν3 or ν1 (UO2)2+) Å. This was found in agreement with U–O bond lengths from the single crystal structure analysis. The number of observed bands supports the conclusion from single crystal structure analysis that at least two symmetrically distinct U6+ (in uranyl) and S6+ (in sulfate), and water molecules and hydroxyls may be present in the zippeite crystal structure. Some O–H…O bond lengths were attributed to the hydrogen-bonding network in zippeite crystal structure.


zippeitepotassium uranyl sulfate mineralchemical formulainfrared and raman spectroscopyu-o bond lengtho-h o bond lengths