Investigation of Americium-Containing Phosphates, Silicates, Borates, Molybdates, and Fluorides Synthesized via...

The crystal chemistry of americium-containing extended structures was investigated, and several classes of americium-containing solid-state oxide materials were obtained in single-crystal form via high-temperature flux crystal growth. This enabled the structural characterization of rare examples of ternary, quaternary, and penternary americium-containing silicates K₃Am (Si₂O₇) and Cs₆Am₂Si₂₁O₄₈, phosphates Na₃Am (PO₄)₂ and K₃Am (PO₄)₂, borates Ba₃Am₂(BO₃)₄ and AmBO₃, borate halides Ca₅Am(BO₃)₄Cl, molybdates Li_0.5Am_0.5MoO₄, and fluorides CsAm₂F₇. Using these crystallographic data, the ionic radii of Am³⁺ with coordination numbers of six (0.975 Å), seven (1.052 Å), and nine (1.162 Å) were established. A maximum entropy method (MEM) analysis was performed on the single-crystal X-ray diffraction data that were collected for K₃Nd(PO₄)₂/K₃Am(PO₄)₂, K₃NdSi₂O₇/K₃AmSi₂O₇, and NdBO₃/AmBO₃, to qualitatively compare the ionicities of the Nd-O and Am-O bonds. Raman spectroscopy data were collected on single crystals of K₃Am(PO₄)₂ and compared to the calculated Raman spectrum of K₃Am(PO₄)₂ obtained from DFT calculations.