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

Preparation, sintering and leaching of optimized uranium thorium dioxides

“…1(A)). All the XRD lines observed were assigned to the orthorhombic Ccca structure already reported for the uranium (IV) oxalate dihydrate (U(C 2 O 4 ) 2 Á 2H 2 O) by Duvieubourg-Garela et al [12]. Also, the best crystallization state was obtained for the precursors prepared under hydrothermal conditions (average FWHM of less than 0.1°versus 0.2°for the 'open system', which nearly corresponds to the resolution of the XRD diffractometer).…”

From uranium(IV) oxalate to sintered UO 2 : Consequences of the powders' thermal history on the microstructure

“…In this study, the preparation of UO 2 powders was undertaken from U(C 2 O 4 ) 2 ·2H 2 O [21,22] in order to study the influence of several precursor-related parameters over the sintering process and the subsequent pellet microstructure. In first place, the variation of the powder characteristics during the conversion step will be detailed, both at the microscopic (crystal structure, carbon content) and macroscopic (morphology, specific surface area) levels.…”

Europium Luminescence as a Structural Probe: Structure‐Dependent Changes in Eu3+‐Substituted Th(C2O4)2·xH2O (x = 6, 2, and 0)

“…[32,33] Owing to the low dopant concentration, no additional signatures from the Eu 3+ ions were observed in any of the XRD patterns. The highly disordered or amorphous nature of the anhydrous phase (TO) was concluded from the broad features in its XRD pattern.…”

“…The structural features of the TOH and TOD have been analyzed and explained previously. [33][34][35] The structural analyses of the TOH and TOD phases indicate that both have eightfold-coordinated Th 4+ ions with four oxalate groups connected to the Th 4+ ions in a bidentate fashion. However, the arrangements of the water molecules around the Th 4+ ions in these two structures are distinctly different.…”

“…[36] Thus, it can be concluded that the origin of the high luminescence intensity of the sample heated to 300°C is the removal of all of the water molecules (or OH -ions), as indicated by the thermogravimetry (TG) and XRD studies. [33] To compare the photoluminescence intensities, the integrated areas under the curves for the magnetic-and electric-dipole transitions were determined at each stage. The relative intensity ratio of the ED to MD transition [called the asymmetry ratio (I)] can be used as a structure-sensitive parameter for understanding the local symmetry around the Eu 3+ ions in the thorium(IV) oxalate host material.…”