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 syntheses of Np, Pu, and Am containing materials to study their crystal chemistry.  This effort has resulted in several new neptunium, plutonium, and americium containing phases including K₃Am(PO₄)₂, K₃AmSi₂O₇, Ba₃Am₂(BO₃)₄, AmBO₃, K₃(NpO₂)Si₄O₁₀, Rb₃(NpO₂)Si₄O₁₀, K₂PuSi₂O₇, and Rb₂PuSi₆O₁₅.  We extended this work to a lower temperature regime where we used ionic liquids as low temperature solvents (fluxes) for the synthesis of new lanthanide and transuranic-element borate clusters. We succeeded in the ionothermal synthesis of new cubic and chiral lanthanum and americium borate clusters, La₄B₂₂O₄₂Cl₁₂,Am₄B₂₂O₄₂Cl₁₂, space group I23.

Phosphates, including monazite-based (LnPO₄) materials are considered to be excellent nuclear waste form candidates and fulfill most of the selection criteria for waste forms. However, the synthesis of the stable anhydrous, monoclinic monazite typically requires the high temperature, ~1,000°C, conversion of rhabdophane (LnPO₄•nH₂O) to monazite, which is impractical for processing large quantities of nuclear waste.  To address this issue, we developed a new synthesis route for the low temperature preparation of polycrystalline monazite phases, LnPO₄, and developed the molten salt syntheses of actinide containing monazite, such as AmPO₄, and monazite related phases, such as Ca_0.5Th_0.5PO₄, and Nd_0.1475Ca_0.305Th_0.5475(SiO₄)_0.24(PO₄)_0.76.

                                                                                                                                                     Monazite crystals of NdPO₄ and AmPO₄

Zhoujin, Y., Tisdale, Y., Keerthisinghe, N., Morrison, G., Smith, M. D., Hadermann, J., Besmann, T. M., Amoroso, J. W., zur Loye, H.-C., “A Low-Temperature, One-Step Synthesis for Monazite Can Transform Monazite into a Readily Usable Advanced Nuclear Waste Form”, DOI:10.1126/sciadv.adt3518.  Sci. Adv., 2025, 11, eadt3518.

Deason, T. K., Grasser, M. A., Mofrad, A. M., Amoroso, J., DiPrete, D. P., Morrison, G., Tisdale, H. B., Pellechia, P. J., Estes, S. L., Smith, M. D., Besmann, T. M., zur Loye, H.-C., “Ionothermal Synthesis of Am₄B₂₂O₄₂Cl₁₂: A Chiral Cubic Americium Borate Cluster”, DOI:10.1021/acs.inorgchem.4c05455.  Inorg. Chem., 2025, 64, 2182-2187.

Deason, T. K., Tisdale, H. B., Hines, A. T., Morrison, G., Zhoujin, Y., Smith, M. D., Besmann, T. M., Mofrad, A. M., Estes, S. L., Amoroso, J. W., DiPrete, D. P., zur Loye, H.-C., “Absence of Americium (Am) Covalency in Extended Structures: Investigation of Americium Containing Phosphates, Silicates, Borates, Molybdates and Fluorides Synthesized via High Temperature Flux Crystal Growth”, DOI:10.1021/jacs.5c03457. J. Am. Chem. Soc., 2025, 147, 21659-21671.