Optical absorption and fluorescence properties of trivalent lanthanide chlorides in high temperature molten LiCl–KCl eutectic

Kim, Bong Young; Yun, Jong-Il

doi:10.1016/j.jlumin.2016.06.010

Cited by 12 publications

(10 citation statements)

References 69 publications

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“…The Sm 3+ ion has five electrons occupying the 4f orbitals and their f−f transitions appear at around 400 nm 19 and 1600 nm. 20,45 Although the transitions between f orbitals of the lanthanide are strictly parity forbidden and many f−f transitions are also spin forbidden, they exhibit weak and narrow adsorption bands because spin−orbit coupling moderately attenuates the forbiddenness. 46 However, these intraconfigurational transitions associated with Sm 3+ are too weak to be observed at a solution concentration such as 2.6 mM, as seen in Figure 3a, which shows electronic absorption spectra obtained from a LiCl-KCl melt containing Sm 3+ with varying potentials in the region where the redox currents of Sm 2+/3+ appear in the CV (Figure 2a).…”

Section: Inorganic Chemistrymentioning

confidence: 99%

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

et al. 2018

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The electrochemical reduction of trivalent samarium in a LiCl-KCl eutectic melt produced highly stable divalent samarium, whose electrochemical properties and electronic structure in the molten salt were investigated using cyclic voltammetry, UV-vis absorption spectroscopy, laser-induced emission spectroscopy, and density functional theory (DFT) calculations. Diffusion coefficients of Sm and Sm were electrochemically measured to be 0.92 × 10 and 1.10 × 10 cm/s, respectively, and the standard apparent potential of the Sm couple was estimated to be -0.82 V vs Ag|Ag at 450 °C. The spectroelectrochemical study demonstrated that the redox behavior of the samarium cations obeys the Nernst equation ( E°' = -0.83 V, n = 1) and the trivalent samarium cation was successfully converted to the divalent cation having characteristic absorption bands at 380 and 530 nm with molar absorptivity values of 1470 and 810 M cm, respectively. Density function theory calculations for the divalent samarium complex revealed that the absorption signals originated from the 4f to 4f5d transitions. Additionally, laser-induced emission measurements for the Sm cations in the LiCl-KCl matrix showed that the Sm ion in the LiCl-KCl melt at 450 °C emitted an orange color of fluorescence, whereas a red colored emission was observed from the Sm ion in the solidified LCl-KCl salt at room temperature.

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Section: Inorganic Chemistrymentioning

confidence: 99%

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

et al. 2018

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“…Likewise, the vibrational bands of the Raman spectra of minority metal ion complexes could be completely masked by the background spectrum of a multivalent host cation. Element-specific optical absorption − and extended X-ray absorption fine-structure (EXAFS , ) spectroscopy represent an excellent probe of the local structure, but the interpretation of the results for complex systems could be very ambiguous. For example, a solute Ni(II) ion in molten ZnCl 2 –alkali chloride mixtures exhibits a very complicated dependence of its coordination geometry on solvent composition and temperature. − Conventional EXAFS analysis assumes that the structural distribution (commonly represented by the pair distribution ( g ( r )) of ions/atoms) can be described by a Gaussian function.…”

Section: Introductionmentioning

confidence: 99%

A Holistic Approach for Elucidating Local Structure, Dynamics, and Speciation in Molten Salts with High Structural Disorder

et al. 2021

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To examine ion solvation, exchange, and speciation for minority components in molten salts (MS) typically found as corrosion products, we propose a multimodal approach combining extended X-ray absorption fine structure (EXAFS) spectroscopy, optical spectroscopy, ab initio molecular dynamics (AIMD) simulations, and rate theory of ion exchange. Going beyond conventional EXAFS analysis, our method can accurately quantify populations of different coordination states of ions with highly disordered coordination environments via linear combination fitting of the EXAFS spectra of these coordination states computed from AIMD to the experimental EXAFS spectrum. In a case study of dilute Ni(II) dissolved in the ZnCl 2 +KCl melts, our method reveals heterogeneous distributions of coordination states of Ni(II) that are sensitive to variations in temperature and melt composition. These results are fully explained by the difference in the chloride exchange dynamics at varied temperatures and melt compositions. This insight will enable a better understanding and control of ion solubility and transport in MS.

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“…In many cases, the signatures of a unique local environment may come in the form of a three-body correlation, such as off-center displacement of a central atom in an octahedral cage. For that purpose, XANES and optical ultraviolet–visible (UV–vis) spectroscopy are powerful probes. − In the disordered environments of molten salts, where the pair distributions of atoms can be far from Gaussian, the applicability of standard EXAFS fitting methods becomes limited − and molecular dynamics (MD) can provide the key to interpretation. ,, We employed each of these approaches to understand these salt and solute systems.…”

Section: Introductionmentioning

confidence: 99%

Connections between the Speciation and Solubility of Ni(II) and Co(II) in Molten ZnCl₂

et al. 2020

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Understanding the factors that control solubility and speciation of metal ions in molten salts is key for their successful use in molten salt reactors and electrorefining. Here, we employ X-ray and optical absorption spectroscopies and molecular dynamics simulations to investigate the coordination environment of Ni(II) in molten ZnCl 2 , where it is poorly soluble, and contrast it with highly soluble Co(II) over a wide temperature range. In solid NiCl 2 , the Ni ion is octahedrally coordinated, whereas the ZnCl 2 host matrix favors tetrahedral coordination. Our experimental and computational results show that the coordination environment of Ni(II) in ZnCl 2 is disordered among tetraand pentacoordinate states. In contrast, the local structure of dissolved Co(II) is tetrahedral and commensurate with the ZnCl 2 host's structure. The heterogeneity and concomitant large bond length disorder in the Ni case constitute a plausible explanation for its lower solubility in molten ZnCl 2 .

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Optical absorption and fluorescence properties of trivalent lanthanide chlorides in high temperature molten LiCl–KCl eutectic

Cited by 12 publications

References 69 publications

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

A Holistic Approach for Elucidating Local Structure, Dynamics, and Speciation in Molten Salts with High Structural Disorder

Connections between the Speciation and Solubility of Ni(II) and Co(II) in Molten ZnCl₂

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Optical absorption and fluorescence properties of trivalent lanthanide chlorides in high temperature molten LiCl–KCl eutectic

Cited by 12 publications

References 69 publications

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

A Holistic Approach for Elucidating Local Structure, Dynamics, and Speciation in Molten Salts with High Structural Disorder

Connections between the Speciation and Solubility of Ni(II) and Co(II) in Molten ZnCl2

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Connections between the Speciation and Solubility of Ni(II) and Co(II) in Molten ZnCl₂