Local structure of molten LaCl3 analyzed by X-ray diffraction and La–LIII absorption-edge XAFS technique

Iwadate, Yasuhiko; Suzuki, Kota; Onda, Nobuhiko; Fukushima, K.; Watanabe, Sou; Matsuura, Haruaki; Kajinami, Akihiko; Takase, Keiichi; Ohtori, Norikazu; Umesaki, Norimasa; Kofuji, Hirohide; Myochin, Munetaka

doi:10.1016/j.jallcom.2005.04.037

Cited by 13 publications

(7 citation statements)

References 26 publications

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“…Glover et al 53 deduced the same coordination number for LaCl 3 -NaCl and LaCl 3 -CsCl systems at infinite dilution in lanthanum. These observations are also supported by Ikawada et al 54 .…”

Section: Methodsmentioning

confidence: 99%

Reactivity of NH₄H₂PO₄ toward LaCl₃ in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO₄.

et al. 2009

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The synthesis of lanthanum phosphates in molten LiCl-KCL eutectic was chosen to address the preliminary treatment of chlorinated wastes containing fission products that are already present in a Li/Cl eutectic. The obtained monazite compound shows interesting properties to be considered as a good candidate to trap lanthanum for a long-time. The synthesis route based on LaCl(3) reaction with NH(4)H(2)PO(4) in a stoichiometric amount is a key point to obtain monazite as a pure phase. Hence, the salt composition is not modified during the synthesis reaction. The chemical reactivity of ammonium dihydrogenphosphate (NH(4)H(2)PO(4), hereafter abbreviated ADP) toward lanthanum chloride (LaCl(3)) in molten LiCl-KCl eutectic is probed by NMR spectroscopy to follow the formation of LaPO(4). Formally, a direct transformation of the two aforementioned precursors into LaPO(4), NH(4)Cl and HCl can be discarded on the basis of the low thermal stability of ADP. To shed some light on the formation of LaPO(4), in situ and ex situ NMR experiments were carried out on LiCl-KCl/LaCl(3)/ADP, as well as LiCl-KCl/ADP, KCl/ADP, and LiCl/ADP mixtures. First, the reactivity of the precursors in contact with the eutectic was studied from room temperature to 600 degrees C by means of (31)P, (35)Cl, and (139)La high temperature NMR. Second, ex situ room temperature magic angle spinning (MAS) and RadioFrequency driven recoupling (RFDR) (31)P solid-state NMR experiments were carried out on solid samples prepared in different conditions (i.e., temperature and atmosphere) and quenched at room temperature to identify frozen intermediate species in their metastable state. On the basis of this approach, we propose a model for the LaPO(4) formation based on a multistep mechanism which highlights the strong reactivity of ADP toward the alkaline salts but without final change in the composition of the solvent.

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Section: Methodsmentioning

confidence: 99%

Reactivity of NH₄H₂PO₄ toward LaCl₃ in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO₄.

et al. 2009

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“…176 This interpretation contrasted with ND studies, which gave somewhat higher N +À . 177 Paradigm of this situation is the interpretation of the work by Iwadata et al, 178 who extracted CNs of 6 and 7 for their respective XRD and EXAFS data. In our opinion, the most likely situation is the one proposed by Madden and co-workers.…”

Section: Iii31 Rare Earth Metal Halidesmentioning

confidence: 99%

Studies of the local structures of molten metal halides

Rollet

Salanne

2011

Annu. Rep. Prog. Chem., Sect. C: Phys. Chem.

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This review covers the local structure of molten metal halide, where a somewhat wide definition of ''local structure'' is employed, i.e. from the first shell of interacting neighbours up to correlations arising at the nanometer length scale. These particular liquids are indeed strongly organized at unusually long distances due to the predominance of coulombic interactions. Many of them are also characterized by the formation of intermediate range ordering. It is therefore impossible to describe the local structure of these liquids omitting this longer-ranged correlation. Finally, a deeper attention is given to the systems on which recent progresses have been made in the last decade, as for instance molten fluorides and rare earth halides.

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“…Yet, these findings were not without some controversy, as at the time, modern polarizable ion models (PIMs) parameterized to include MCl 3 salts − such as ScCl 3 , YCl 3 , TbCl 3 , and LaCl 3 in cases resulted in integrated pair distribution functions (PDFs) in which the coordination numbers were simply too large for the prevalent picture of octahedral complexes or aggregates apparently supported by Raman experiments . X-ray absorption fine structure (XAFS) ,− and X-ray , scattering data on the coordination structure of La 3+ were also reported as difficult to reconcile, given that XAFS , suggested larger than the originally postulated octahedral coordination. The interpretation by Madden and co-workers ,,− ,, of the coordination of La 3+ including their calculation of Raman spectra is, in our view, significantly more nuanced and accurate, as it highlights that the six-coordinate structure should only be expected at a low La 3+ concentration.…”

Section: Introductionmentioning

confidence: 99%

Complete Description of the LaCl₃–NaCl Melt Structure and the Concept of a Spacer Salt That Causes Structural Heterogeneity

et al. 2022

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Lanthanides are important fission products in molten salt reactors, and understanding their structure and that of their mixtures is relevant to many scientific and technological problems including the recovery and separation of rare earth elements using molten salt electrolysis. The literature on molten salts and specifically on LaCl 3 and LaCl 3 −NaCl mixtures is often fragmented, with different experiments and simulations coinciding in their explanation for certain structural results but contradicting or questioning for others. Given the very practical importance that actinide and lanthanide salts have for energy applications, it is imperative to arrive at a clear unified picture of their local and intermediate-range structure in the neat molten state and when mixed with other salts. This article aims to unequivocally answer a set of specific questions: is it correct to think of long-lived octahedral coordination structures for La 3+ ? What is the nature as a function of temperature of networks and intermediate-range order particularly upon dilution of the trivalent ion salt? Is the so-called scattering first sharp diffraction peak (FSDP) for neat LaCl 3 truly indicative of intermediate-range order? If so, why is there a new lower-q peak when mixed with NaCl? Are X-ray scattering and Raman spectroscopy results fully consistent and easily described by simulation results? We will show that answers to these questions require that we abandon the idea of a most prominent coordination state for M 3+ ions and instead think of multiple competing coordination states in exchange due to significant thermal energy in the molten state.

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Local structure of molten LaCl3 analyzed by X-ray diffraction and La–LIII absorption-edge XAFS technique

Cited by 13 publications

References 26 publications

Reactivity of NH₄H₂PO₄ toward LaCl₃ in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO₄.

Reactivity of NH₄H₂PO₄ toward LaCl₃ in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO₄.

Studies of the local structures of molten metal halides

Complete Description of the LaCl₃–NaCl Melt Structure and the Concept of a Spacer Salt That Causes Structural Heterogeneity

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Local structure of molten LaCl3 analyzed by X-ray diffraction and La–LIII absorption-edge XAFS technique

Cited by 13 publications

References 26 publications

Reactivity of NH4H2PO4 toward LaCl3 in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO4.

Reactivity of NH4H2PO4 toward LaCl3 in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO4.

Studies of the local structures of molten metal halides

Complete Description of the LaCl3–NaCl Melt Structure and the Concept of a Spacer Salt That Causes Structural Heterogeneity

Contact Info

Product

Resources

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Reactivity of NH₄H₂PO₄ toward LaCl₃ in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO₄.

Reactivity of NH₄H₂PO₄ toward LaCl₃ in LiCl-KCl Melt Flux. Step by Step Formation of Monazite-Like LaPO₄.

Complete Description of the LaCl₃–NaCl Melt Structure and the Concept of a Spacer Salt That Causes Structural Heterogeneity