Incorporation of U(IV) in monazite–cheralite ceramics under oxidizing and inert atmospheres - Archive ouverte HAL Access content directly
Journal Articles Dalton Transactions Year : 2024

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

Adel Mesbah
Denis Menut
Nicolas Dacheux

Abstract

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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