Relations d'isomorphisme dans la série des oxalates hydrates de thorium et d'uranium

Adaptable coordination of U(IV) in the 2D-(4,4) uranium oxalate network: From 8 to 10 coordinations in the uranium (IV) oxalate hydrates

“…Refinement from the PXRD pattern (Fig. 2b) of the unit cell parameters gives a ¼ 8.5449(8), b ¼ 10.494(7) and c ¼ 9.419(8) Å for 2 in agreement with the previously reported results [24,25] (PDF 22-0961).…”

“…The existence of hexa-, di-, mono-hydrated and anhydrous U(IV) oxalates has been reported. Jenkins et al [24] and Bressat et al [25] gave a triclinic cell, with a ¼ 6.388(3), b ¼ 6.388(3), c ¼ 7.881(4) Å , a ¼ 91.64(1), b ¼ 91.64(1), g ¼ 89.45(1)1, for the uranium oxalate hexahydrate U(C 2 O 4 ) 2 Á 6H 2 O and an orthorhombic cell with face centered lattice, with a ¼ 10.479(3), b ¼ 9.443(3), c ¼ 8.572(3) Å , for the uranium oxalate dihydrate U(C 2 O 4 ) 2 Á 2H 2 O. By analogy with the neptunium analogue, Grigoriev et al [26] propose to transform the triclinic cell of the uranium (IV) hexahydrate into a monoclinic one with parameters a ¼ 9.081(4), b ¼ 8.893(4), c ¼ 7.878(4) Å , b ¼ 92.…”

Synthesis and characterization of Th1−xLnxO2−x/2 mixed-oxides

“…Although this band was observed for all the samples presenting a C-type phase from XRD results, it was also clearly evidenced in the m-Raman spectra of Th 0. 66 (Fig. 4).…”

“…Conversely, the majority of the solid was nonetheless constituted by the F-type phase and the C-type phases detected by m-Raman for Th 0. 66 …”

X-Ray Diffraction and μ-Raman Investigation of the Monoclinic-Orthorhombic Phase Transition in Th1−xUx(C2O4)2·2H2O Solid Solutions

“…Finally, the crystal structure of tetravalent actinide oxalates mainly varies with the hydration of the samples. Indeed, a triclinic structure was reported in the mid 1960s for An IV (C 2 O 4 ) 2 3 6H 2 O (An IV =Th, U, Np, Pu) from powdered compounds by Bressat et al 26 and Jenkins et al 27 before it was assumed to be a monoclinic lattice from the data collected on neptunium-based single crystals as reported by Grigor'ev et al 28 For dihydrated An IV (C 2 O 4 ) 2 3 2H 2 O (An IV = Th, U) compounds, an orthorhombic lattice is generally assumed. 16,27 On this basis, the preparation of oxalate precursors of Th 1-x U x O 2 (0 e x e 1) solid solutions from hydrothermal conditions was undertaken in this work.…”