Microstructure and physical properties of superionic eutectic composites of the LiF–RF3 (R=rare earth element) system

Trnovcová, V.; Федоров, П. П.; Bárta, Č.; Labaš, Vladimír; Meleshina, V. A.; Соболев, Б. П.

doi:10.1016/s0167-2738(98)00500-1

Cited by 31 publications

(24 citation statements)

References 2 publications

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“…13,14 More recent work has shown lamellar structures for LiF-LnF 3 (where Ln D La or Pr), fibrous for LiF-GdF 3 or a mixture of the two (for Ln D Nd or Sm). 15,16 A lamellar structure was claimed 17 for PbF 2 -ScF 3 . LiF-CaF 2 eutectic has also been found to give lamellar structures.…”

Section: Discussionmentioning

confidence: 98%

Raman mapping in the elucidation of solid salt eutectic and near eutectic structures

Berg

Kerridge

2002

J Raman Spectroscopy

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The distribution of the different components of solidified eutectic or near-eutectic salt mixtures (eutectics) was examined by use of Raman microscope mapping of the structures formed when these melts were slowly cooled. Seven binary and one ternary system were investigated. In most cases the component crystallized phases consisted of roughly rounded areas of about 0.5-5 µm across, the areas alternating in all directions across the sections. These three-dimensional structures may best be described by the term 'conglomerate.' The size of these areas depended on the cooling rate and the composition. When unidirectional cooling was applied it was possible for the system (KCl-Na 2 SO 4 , 60 : 40 mol/mol) to observe lamellar arrangements of the component phases, in an arrangement closely similar to what is frequently found among metallic or ceramic eutectics. Each area, conglomerate or lamellar, did not consist of a pure chemical component, although having one component in a high concentration. Probably the behaviour represents separation on solidification due to the limiting solid solubility. The 'conglomerate' structures are very different from what has been found for metallic or ceramic eutectics. Small changes in composition, in sectioning direction and in solidification technique were found to result in relatively small differences. The major effect was found to result from the rate of solidification, faster cooling causing markedly smaller rounded areas with the 'conglomerate' becoming much finer grained. The high area of 'interphasial' contact between the solid solutions is considered to be responsible for the unexpectedly high electrical conductivity previously found and to give rise to part of the melting enthalpy differences between those of solidified salt eutectics and those of the corresponding unmelted mechanical mixtures of the component salts. Mixtures with a larger variation away from the eutectic composition also showed a 'conglomerate' structure, but with bigger and more irregular areas.

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Section: Discussionmentioning

confidence: 98%

Raman mapping in the elucidation of solid salt eutectic and near eutectic structures

Berg

Kerridge

2002

J Raman Spectroscopy

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“…The high-pressure forms of LaF 3 and CeF 3 (Cmma, Z = 8) are distorted modifications of hypothetical fluorite-like trifluoride [20]. At atmospheric conditions, the tysonite or fluocerite structures allow non-stoichiometric solid solutions and composites in the systems LiF-RF 3 [21] and NaF-RF 3 [22] (R = rare earth element). The LiF-GdF 3 phase diagram has two invariant points: a eutectic at 25 mol% GdF 3 and 973 K as well as a peritectic at 34 mol% GdF 3 and 1023 K [23].…”

Section: Discussionmentioning

confidence: 99%

Two-Dimensional Simulation of Nonlinear Acoustic Wave Propagation Using Constrained Interpolation Profile Method

Konno¹,

Okubo²,

Tsuchiya

et al. 2009

Jpn. J. Appl. Phys.

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The high-pressure behaviour of LiGdF 4 scheelite (I 4 1 /a, Z = 4) was studied by measuring its angle-dispersive x-ray powder diffraction patterns as a function of pressure and temperature in a diamond anvil cell and a large-volume Paris-Edinburgh cell using a synchrotron radiation source. Upon compression to about 11 GPa at room temperature, the stable structure is of the scheelite type. At higher pressures and T = 298 K, new reflections occur that cannot be explained with the fergusonite structural model previously observed for LiYF 4 . Associated with this is the growth of an amorphous component. All the transformations are largely irreversible upon decompression. Annealing of the sample at 13.1 GPa led to a nucleation of a solid solution series Li y Gd 1−y F 3−2y (P6 3 /mmc, Z = 2) and traces of LiF. The new material Li y Gd 1−y F 3−2y (P6 3 /mmc, Z = 2) was recovered to ambient conditions but back-transformed to a YF 3 -type phase (Pnma, Z = 4) after regrinding at room temperature for several hours. These observations are discussed in relation to the high-pressure high-temperature systematics of the AMX 4 -type compounds.

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“…However, the volume fraction ratio of the two eutectic phases can lead to the formation of lamellar, fibrous, or mixed microstructures. In general, when both phases have comparable volume fractions, a lamellar structure is formed [23]. Due to the fast cooling using liquid nitrogen in all four systems, a fine eutectic structure with small alternations LiF and NdF 3 lamellar is formed (Figs.…”

Section: Microstructurementioning

confidence: 92%

“…5 indicates that the microstructure corresponds to a non-eutectic phase. With the increasing growth velocity, the dimensions of the two phases are expected to decrease [23,24].…”

Section: Microstructurementioning

confidence: 99%

Electrochemical Extraction of Rare Earth Metals in Molten Fluorides: Conversion of Rare Earth Oxides into Rare Earth Fluorides Using Fluoride Additives

Abbasalizadeh

Malfliet

Seetharaman

et al. 2017

J. Sustain. Metall.

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In the present research on rare earth extraction from rare earth oxides (REOs), conversion of rare earth oxides into rare earth fluorides with fluoride fluxes is investigated in order to overcome the problem of low solubility of the rare earth oxides in molten fluoride salts as well as the formation of oxyfluorides in the fluorination process. Based on thermodynamic calculations, a series of experiments were performed for converting the rare earth oxides into rare earth fluorides using AlF 3 , ZnF 2 , FeF 3 , and Na 3 AlF 6 as fluorinating agents in a LiF-Nd 2 O 3 system. The formation of neodymium fluoride as a result of the reactions between these fluxes and neodymium oxide is confirmed. The rare earth fluoride thus formed can subsequently be processed through the electrolysis route in the same reactor, and rare earth metal can be produced as the cathodic deposit. In this concept, the REO dissolution in molten fluorides would become unnecessary due to the complete conversion of the oxide into the fluoride, REF 3 . The results of XRD and EPMA analysis of the reacted samples indicate that AlF 3 , ZnF 2 , and FeF 3 can act as strong fluorinating agents for the neodymium oxide giving rise to a complete conversion of neodymium oxide into neodymium fluoride.

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Microstructure and physical properties of superionic eutectic composites of the LiF–RF3 (R=rare earth element) system

Cited by 31 publications

References 2 publications

Raman mapping in the elucidation of solid salt eutectic and near eutectic structures

Raman mapping in the elucidation of solid salt eutectic and near eutectic structures

Two-Dimensional Simulation of Nonlinear Acoustic Wave Propagation Using Constrained Interpolation Profile Method

Electrochemical Extraction of Rare Earth Metals in Molten Fluorides: Conversion of Rare Earth Oxides into Rare Earth Fluorides Using Fluoride Additives

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