From Mild Hydrothermal to High Temperature Solutions: Crystal Growth of New Actinide Phases.


Our interest in finding suitable waste forms for the effective immobilization of minor actinides in persistent architectures has led us to explore the molten salt and hydrothermal syntheses of Np, Pu, Am, and Cm containing materials to study their structures, learn about their bonding, and to evaluate the radiation resilience of such materials.  In the case of Am and Cm we are also interested in assessing how good a surrogate Nd or Pr are for Am and Cm and to learn more about their crystal chemistry. We performed DFT calculations to estimate the stability of the target compositions to increase the success rate of our syntheses. Using this information we pursued the crystal growth of americium containing oxides and fluorides in molten salt environments, which has resulted in several new americium containing phases, including K3Am(PO4)2, K3AmSi2O7, and CsAm2F7.  We have solved the single crystal structures of these phases as well as synthesized single crystals of their surrogate containing analogs, whose structures we also determined.
In a separate DOE funded project, we developed a convenient methodology to prepare actinide chalcogenides starting from oxide reagents.  A short overview of this method and the types of materials that can be prepared using it will also be presented.

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