EPR and luminescence studies of Eu(II) magnetically diluted in LiCl–KCl salt

Kim, Tack-Jin; Cho, Young-Hwan; Choi, In‐Kyu; Kang, Ji-Hoon; Jee, Kwang Yong

doi:10.1016/j.jlumin.2007.04.008

Cited by 22 publications

(6 citation statements)

References 8 publications

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“…Best fits are achieved with g = 1.95(2). This value is slightly smaller than results of other inorganic europium(II) compounds in the literature, − corroborating the collective nature of the excitation at this temperature. Simulations with a spin of 7/2 and small values for the zero-field splitting do not yield an acceptable result.…”

Section: Discussionsupporting

confidence: 81%

Old and New Insights into Structure and Properties of Eu₂[SiO₄]

Funk

Köhler

Lazar

et al. 2018

Crystal Growth & Design

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Lemon-yellow single crystals of Eu2[SiO4] were obtained by reaction of elemental europium with Eu2O3 in the presence of SiO2 carried out in evacuated silica ampules at 1373 K for 48 h followed by constant cooling to room temperature with 120 K per hour. Eu2[SiO4] crystallizes at room temperature in the larnite-type structure of β-Ca2[SiO4] (monoclinic, P21/n) with parameters a = 565.02(5), b = 709.15(6), c = 975.84(8) pm, β = 92.614(3)° for Z = 4. At 452 K it undergoes a reversible phase transition to an incommensurate structure similar to the isotypic compounds Sr2[SiO4] and K2[SeO4]. The phase transition energy was determined to 0.54(2) J·g–1 by DSC measurements and temperature dependent birefringence measurements show that the phase transition exhibits a significant hysteresis. Refinements of the structure of Eu2[SiO4] based on single crystal X-ray diffraction data show that the high temperature modification crystallizes in the orthorhombic space group Pnma(α00)0ss with a = 710.16(6), b = 566.93(5), c = 977.13(8) pm, and an incommensurate modulation along [100] with a modulation vector t = [0.293(4), 0, 0]. Eu2[SiO4] exhibits a bright yellow photoluminescence and its permittivity increases substantially above 300 K. Magnetic susceptibility and EPR measurements show that Eu2[SiO4] becomes ferromagnetic below 7 K with a g factor of 1.993.

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Section: Discussionsupporting

confidence: 81%

Old and New Insights into Structure and Properties of Eu₂[SiO₄]

Funk

Köhler

Lazar

et al. 2018

Crystal Growth & Design

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“…[10][11][12]18,19 Eu(III) is reduced to Eu(II) immediately after adding them into the molten chloride salt. The redox reaction can be simply described as follows: 8,10 2EuCl 3 ↔ 2EuCl 2 + Cl 2 [1] Fig.…”

Section: Resultsmentioning

confidence: 99%

“…This divergent result requires the reliable technique for in situ quantitative analysis of reduction of trivalent europium. Recently, several groups have measured the fluorescence spectrum of Eu(II) in LiCl-KCl eutectic at various temperatures, [11][12][13] whereas the fluorescence spectrum of Eu(III) have not been observed in high-temperature LiCl-KCl eutectic. The fluorescence intensity of Eu(II) did not obey linear relationship against the concentrations, so that the quantitative analysis of redox behavior of Eu(III) have not been performed based on the results from fluorescence measurements in high-temperature molten salt.…”

mentioning

confidence: 99%

Reduction of Trivalent Europium in Molten LiCl-KCl Eutectic Observed by In-Situ Laser Spectroscopic Techniques

Kim

Yun

2013

ECS Electrochemistry Letters

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The in-situ quantification for the reduction of Eu(III) was performed in the LiCl-KCl eutectic at various temperatures by time-resolved laser fluorescence spectroscopy (TRLFS) and UV-Vis absorption spectroscopy. From the results of absorption measurement, Eu(III) virtually underwent complete reduction to Eu(II) under the present experimental conditions, while TRLFS revealed a relatively greater reducing power of Eu(III) in the chloride molten eutectic with decreasing its concentration and increasing temperature. However, it was convincingly identified that fluorescence measurements deliver more reliable quantification, compared with the UV-Vis absorption measurements, showing a mutually hindered overlap of absorption bands of Eu(II) and Eu(III).The molten chloride salt is one of the ionic liquid solvents used in the electrorefining and electrowinning of pyrochemical process for recycling used nuclear fuel. Over the past decade, thermodynamic and electrochemical behaviors of actinides and lanthanides in molten chloride salts have been investigated to understand fundamental knowledge and reaction mechanism. 1 An efficient separation of some lanthanides is essential due to their high neutron capture crosssection. Particularly, europium is an attractive and motivating element among lanthanides because of its presence in the multiple oxidation state. Although most lanthanides exist in the trivalent valence state in molten salts, europium can be present in the mixed valence states of Eu(II) and Eu(III) which are likely to cause circulating current in the electrolysis process. 2,3 For that reason, the efficiency of electrolysis during electrorefining and electrowinning process is undoubtedly affected by circulation current arising from alternate reduction and redox reactions at the electrode.The thermodynamic properties of europium ions in molten alkali chloride salt have been studied by electrochemical methods. 3-8 The qualitative and quantitative analysis of reduction of europium from Eu(III) to Eu(II) has been performed in molten alkali chloride salts by electrochemical method, 9,10 absorption spectroscopy, 10 and electron paramagnetic resonance (EPR) technique. 11 Nevertheless, there has been still a relatively large discrepancy of the reducing capacity of europium in chloride molten salts reported in literatures. Kim et al. 10 reported that around 20% of Eu(III) was reduced to Eu(II) at 5.4 × 10 −4 M by absorption spectroscopy and electrochemical analysis in high temperature, and Park et al. 11 observed that approximately 50% of Eu(III) was reduced to Eu(II) measured by EPR technique at room temperature after solidification of molten salt samples. This divergent result requires the reliable technique for in situ quantitative analysis of reduction of trivalent europium. Recently, several groups have measured the fluorescence spectrum of Eu(II) in LiCl-KCl eutectic at various temperatures, 11-13 whereas the fluorescence spectrum of Eu(III) have not been observed in high-temperature LiCl-KCl eutectic. The fluorescen...

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“…Samarium (Sm), , europium (Eu), and ytterbium (Yb) form stable and soluble divalent ions, as well as trivalent ones, in the molten salt unlike other lanthanides, which exist exclusively as trivalent ions in the melt. Moreover, these divalent ions can be electrochemically deposited as alloys in reactive solid electrodes and liquid electrodes, though their electrodeposition on a stable solid electrode is beyond the potential window offered by the molten salt.…”

Section: Introductionmentioning

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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EPR and luminescence studies of Eu(II) magnetically diluted in LiCl–KCl salt

Cited by 22 publications

References 8 publications

Old and New Insights into Structure and Properties of Eu₂[SiO₄]

Old and New Insights into Structure and Properties of Eu₂[SiO₄]

Reduction of Trivalent Europium in Molten LiCl-KCl Eutectic Observed by In-Situ Laser Spectroscopic Techniques

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

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EPR and luminescence studies of Eu(II) magnetically diluted in LiCl–KCl salt

Cited by 22 publications

References 8 publications

Old and New Insights into Structure and Properties of Eu2[SiO4]

Old and New Insights into Structure and Properties of Eu2[SiO4]

Reduction of Trivalent Europium in Molten LiCl-KCl Eutectic Observed by In-Situ Laser Spectroscopic Techniques

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

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Old and New Insights into Structure and Properties of Eu₂[SiO₄]

Old and New Insights into Structure and Properties of Eu₂[SiO₄]