Incorporation of U(IV) in monazite–cheralite ceramics under oxidizing and inert atmospheres - Axe 1 : procédés céramiques
Article Dans Une Revue Dalton Transactions Année : 2024

Incorporation of U(IV) in monazite–cheralite ceramics under oxidizing and inert atmospheres

Alison El Monjid
Adel Mesbah
Denis Menut
Nicolas Clavier
Nicolas Dacheux

Résumé

This work is the first attempt to prepare Nd$_1$$_−$$_x$Ca$_x$U$_x$PO$_4$ monazite–cheralite with 0 < x ≤ 0.1 by a wet chemistry method. This method relies on the precipitation under hydrothermal conditions (T = 110 °C for four days) of the Nd$_1$$_−$$_x$Ca$_x$U$_x$PO$_4$·nH2O rhabdophane precursor, followed by its thermal conversion for 6 h at 1100 °C in air or Ar atmosphere. The optimized synthesis protocol led to the incorporation of U and Ca in the rhabdophane structure. After heating at 1100 °C for 6 h in air, single-phase monazite–cheralite samples were obtained. However, α-UP$_2$O$_7$ was identified as a secondary minor phase in the samples heated under Ar atmosphere. The U speciation in the samples converted in an oxidising atmosphere was carefully characterized using synchrotron radiation by combining HERFD-XANES and XRD. These results showed the presence of a minor secondary phase containing hexavalent uranium and phosphate with a stoichiometry of U : P = 0.78. This highly labile uranyl phosphate phase incorporated 21 mol% of the uranium initially precipitated with the rhabdophane precursor. This phase was completely removed by a washing protocol. Thus, single-phase monazite–cheralite was obtained through the wet chemistry route described in this work with a maximum U loading of x = 0.08.
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hal-04558643 , version 1 (25-04-2024)

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Alison El Monjid, Stéphanie Szenknect, Adel Mesbah, Myrtille O J Y Hunault, Denis Menut, et al.. Incorporation of U(IV) in monazite–cheralite ceramics under oxidizing and inert atmospheres. Dalton Transactions, 2024, 53 (5), pp.2252-2264. ⟨10.1039/D3DT03251E⟩. ⟨hal-04558643⟩
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