Spectral properties of ultrafine systems LaF3 and EuF3 in a frozen melt NaCl-KCl
This paper presents the results of studying by spectral methods (IR transmittance spectroscopy, diffuse reflectance (DR) spectroscopy, luminesce spectroscopy) of solidified solutions-melts of LaF3 and EuF3 in the saline system NaCl-KCl. A preliminary assessment of fluoride solubility on the basis of thermodynamic calculations of exchange reactions in the melt gave values of about 0.74 and 0.29% by weight, respectively, for LaF3 and EuF3 at 700°C. IR spectra of solidified solutions-melts contain a clear band in the range of 250-260 cm-1, corresponding to NaCl, and a less expressive band at 206-210 cm-1 (KCl). At the same time, the IR spectra of the undissolved residues also contain bands in the range of 360-390 cm-1, corresponding to the Ln – F bonds. The DR spectra of LaF3 in NaCl-KCl contain a deep band in the negative region at 245 nm, which corresponds to the intrinsic luminescence of NaCl, in the absence of its own absorption bands of La3+ ions. An analogous band is observed in the EuF3 DR spectra in NaCl-KCl, while it overlaps with the luminescence excitation band of Eu2+ at 350 nm. These bands are also contained in the DR spectra of the undissolved residue, while their intensity is much lower. In the range of 1800-2200 nm, in this case, the absorption band characteristic of Eu3+, consisting of several peaks of different intensities, also manifests itself. The possibility of a redox reaction between Eu3+ and Cl- ions is shown. The luminescence spectrum of LaF3 in saline melt is a broad band of middle intensity with a maximum at 460 nm. In the case of salt melt with EuF3, the luminescence band has the form of a rather narrow peak of high intensity with a maximum at 430-440 nm. In addition, a low-intensity emission band is detected, consisting of several peaks in the range of 500–700 nm, which is due to its appearance to 4f - 4f electronic transition in Eu3+. A similar absorption band takes place in the undissolved residue, while its intensity is much higher.
Beliaiev Y.N., Lupeyko T.H., Nalbandian V.Y., Nalbandian V.B. Saline melts in chemistry and technology of complex oxides II. Saline melts as media for synthesis of polycrystalline complex oxides. In: Ionnye rasplavy s tviordyie elektrolity. (Kiev: Naukova dumka). 1987.2: 1. [in Russian].
Volkov S.V., Malyovanyi S.M., Panov E.V. Synthesis of nanosized powders of Titanium and Zirconium mixed oxides from nitrate melts. Russian Journal of Inorganic Chemistry. 2002. 47(11): 1603. [in Russian].
Komarneni S., Ravella R., Park M. Swelling mica-type clays: synthesis by NaCl melt method, NMR characterization and cation exchange selectivity. J. Mater.Chem. 2005. 15: 4241. https://doi.org/10.1039/b509682k
Priya M., Mahadevan C.K. Preparation and dielectric properties of oxide added NaCl-KCl polycrystals. Physica B. 2008. 403: 67. https://doi.org/10.1016/j.physb.2007.08.009
Gupta A., Sil A., Verma N.K. Preparation, characterization and ionic conductivity studies of ZrO2 dispersed mixed halide matrix (KCl)0.9-(NaCl)0.1. J. Phys. Chem. Solids. 2009. 70: 340. https://doi.org/10.1016/j.jpcs.2008.10.029
Tarasenko S.O., Zinchenko V.F., Timukhin Ye.V., Zhykharieva Ye.O., Kovalevska I.P. Interaction and solubility of fluorides of metals in saline melt NaCl-KCl. Ukr. Khim. Zhurn. 2008. T.74(2): 71. [in Ukrainian].
Zinchenko V.F., Timukhin Ie.V., Pavlinchuk S.A., Nechiporenko A.V., Sadkovskaia L.V. Basicity-acidity and solubility of metal fluorides and oxides in salt melts. Russian Journal of Electrochemistry. 2012. 48(10): 995. https://doi.org/10.1134/S102319351210014X
Zinchenko V.F., Nechiporenko A.V., Ieriomin O.G., Timukhin Ie.V., Meshkova S.B., Stoianov A.O., Doga P.G., Dyshleva L.F. Nanostructures of Europium fluorides in saline systems: synthesis and spectral properties. Nano-technics. 2014. 3: 48. [in Russian].
Ambrová M., Jurišová J., Danielik V., Gabčová J. On the solubility of Lanthanum oxide in molten alkali fluorides. J. Therm. Anal. Calorimetry. 2008. 91(2): 569. https://doi.org/10.1007/s10973-007-8533-6
Pshenychnyi R.M., Savchuk R.M., Samchuk A.I., Omelchuk A.O. Interaction of oxides of Rare-Earth and transition metals in the LiF-NaF eutectics melt. Ukr. Khim. Zhurnal. 2010. 76(9): 12. [in Ukrainian].
Pshenichnyi R.N., Omelchuk A.A. Solubility of d- and f-element oxides in molten mixtures of alkaline metal fluorides and Zirconium tetrafluoride. In: Physical Chemistry and electrochemistry of molten and solid electrolytes: Proc. XVI Russian conf. (with intl. participation) (Sept., 2013, Ekaterinburg, RF). 1: 278. [in Russian].
Zinchenko V.F., Omelchuk A.A., Timukhin Ie.V. Prognostication and thermodynamic estimation of solubility of compounds in saline melts. In: Physical Chemistry and electrochemistry of molten and solid electrolytes: Proc. XVI Russian conf. (with intl. participation) (Sept., 2013, Ekaterinburg, RF). 1: 99. [in Russian].
Surin I.G., Spitsyn P.K., Barkovskiy V.F. Study of the interaction of Rare-Earths with arsenazo III in the domain of 0.5÷4.0 // Zhurnal analiticheskoy khimii. 1979. 34(6): 1103. [in Russian].
Binnewies M., Milke E. Thermochemical Data of Elements and Compounds Second, Revised and Extended Edition. Weinheim: Wiley VCH Verlag GmbH, 2002: 928 https://doi.org/10.1002/9783527618347
Kochubei V.Y. Formation and properties of luminescence centers in alkaline-halide crystals. Moscow: Fiziko-matematycheskaia literature. 2006: 190
Jun-Gill K., Min-Kook N., Yongku S. Luminescence from KCl co-doped with Eu2+ and Eu3+ ions. J.Phys. Condens. Matter. 2000. 12(10): L199. https://doi.org/10.1088/0953-8984/12/10/101
Kuznetsov S.A., Rycerz L., Gaune-Escard M. Electrochemical and thermodynamic properties of EuCl3 and EuCl2 in equimolar NaCl-KCl melt. Z. Naturforsch. 56a. 2001: 741. https://doi.org/10.1515/zna-2001-1108
Kuznetsov S.A., Gaune-Escard M. Electronic conductivity of NaCl-KCl equimolar melt containing Eu(III) and Eu(II) complexes by electrochemical impedance spectroscopy. Z. Naturforsch. 61a. 2006: 486. https://doi.org/10.1515/zna-2006-0906
Brown D. Halides of the transition elements. Halides of the lanthanides and actinides (London-New York-Sydney: A. Willey-Interscience Publication, John Willey and Sons Ltd, 1969).