Spectral properties of ultrafine systems LaF3 and EuF3 in a frozen melt NaCl-KCl

  • V. F. Zinchenko A.V. Bogatsky Physico-Chemical Institute of NAS of Ukraine https://orcid.org/0000-0002-5761-8616
  • G. V. Volchak A.V. Bogatsky Physico-Chemical Institute of NAS of Ukraine
  • O. G. Ieriomin A.V. Bogatsky Physico-Chemical Institute of NAS of Ukraine
  • I. V. Stoyanova A.V. Bogatsky Physico-Chemical Institute of NAS of Ukraine
  • N. O. Chivirova A.V. Bogatsky Physico-Chemical Institute of NAS of Ukraine
  • S. V. Kuleshov V.I. Vernadsky Institute of General and Inorganic Chemistry of NAS of Ukraine
  • P. G. Doga A.V. Bogatsky Physico-Chemical Institute of NAS of Ukraine
Keywords: Saline melts, Lanthanum and Europium fluorides, solubility, spectral properties, absorption and emission bands

Abstract

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.

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Published
2019-10-30
How to Cite
Zinchenko, V. F., Volchak, G. V., Ieriomin, O. G., Stoyanova, I. V., Chivirova, N. O., Kuleshov, S. V., & Doga, P. G. (2019). Spectral properties of ultrafine systems LaF3 and EuF3 in a frozen melt NaCl-KCl . Surface, (11(26), 394-402. https://doi.org/10.15407/Surface.2019.11.394
Section
Physics and chemistry of surface phenomena