Molten Flux Synthesis of Plutonium (IV) Silicates K2PuSi2O7 and Rb2PuSi6O15

Abstract

Few plutonium containing silicates have been reported in the literature and only one other tetravalent plutonium silicate structure has been reported using the flux growth method. With the goal of understanding actinide incorporation into silicates, we describe herein two new plutonium (IV) silicates, Rb2PuSi6O15 and K2PuSi2O7, synthesized using a mixed alkali chloride/alkali fluoride flux growth. Both structures crystallize in the C2/c space group with lattice parameters a = 24.2980(10) Å, b = 7.1466(3) Å, c = 17.2025(8) Å and 𝛽 = 96.6560(10)o for Rb2PuSi6O15, and a = 9.9478(2) Å, b = 5.59820 (10) Å, c = 13.1848(2) Å, and 𝛽 = 105.7400(10)o for K2PuSi2O7. Comparisons to the synthesis of other reported alkali actinide silicates (Ce, U, and Th) are made. Raman spectra and DFT calculations of formation enthalpies and vibrational modes provide confirmation of structure refinements and enhanced product characterization for comparison with other materials.