Raman spectra of tetragonal lanthanide oxychlorides obtained from polycrystalline and single‐crystal samples

Abstract

The reported Raman spectra of the tetragonal [lead chlorofluoride-type structure, D~,,-PCl/nmm (ITC No. 129)l lanthanide oxychlorides are inconsistent. Nuclear site symmetry analysis predicts six Raman bands. Five peaks are consistently observed, whereas the sixth remains controversial. Also, two different sets of irreducible representations are reported : 2A,, + 3Eg + Bza (or B I J + 3A2, + 3E, which include the three acoustic modes, A*,{ T,} and Em{ T,, T J . The present analysis of the polarized Raman spectra from PrOCl and NdOCl single crystals clearly showed that the correct irreducible representation contains the B, symmetry. The symmetries of three Raman-active bands are weU determined, a fourth band displays two polarizations and a fifth band has no clear polarization and is assigned E, by default. The EuOCl Raman spectrum exhibits a weak electronic Raman band which originates in electron-phonon coupling as a result of the closeness between the vibrational and electronic eigenvalues. The low-energy band (LaOCI, 67 cm-'; EuOCI, 70 cm-'; and GdOC1, 65 cm-') and the high-energy band (525 cm-' for LaOCl) reported by others for selected lanthanide oxychlorides were not observed in the present work.

Investigation of the Structural Properties of an Extended Series of Lanthanide Bis-hydroxychlorides Ln(OH)2Cl (Ln = Nd−Lu, except Pm and Sm)

“…Thus, it is expected that related actinide(III) complexes can be prepared by applying similar techniques and methods. A number of workers have shown that this is possible and that the structural and physicochemical properties of these 4f and 5f complexes compare well. − We, therefore, expect that the work described here can well be extended to the radioactive actinide elements and not only enhance the fundamental knowledge of f-element chemistry but also suggest implications for the long-term isolation and safe storage of spent nuclear fuels.…”

Low Temperature Chlorination of Nd<sub>2</sub>O<sub>3</sub> by Mechanochemical Method with CCl<sub>4</sub>

“…As for the peak shift of Raman spectra, the most of NdOCl spectrum peaks in the products obtained in our mechanochemical experiments were shifted to lower wavenumbers than those of tetragonal NdOCl crystals [19], and they were considered to be influence of the residual stress by a milling as described above sections. According to the Raman spectroscopy measurements of Cr 2 O 3 thin films [28], Y 2 O 3 -ZrO 2 barrier coatings [29], epitaxial GaN layers [30], and Al 2 O 3 single crystals [31], in the state where the stress was applied, the redshift which the peak shifted to low wavenumbers was based on the tensile stress, and the tensile stress remained in the surface of products which obtained by using a planetary ball mill.…”

“…In order to confirm the possibility of chlorination from Nd 2 O 3 with CCl 4 in a tungsten carbide pot and to compare a product obtained in a zirconia pot with that in a tungsten carbide pot, the mechanochemical experiments were conducted in the same condition by a milling at 500 . The Raman shifts of tetragonal NdOCl are 118, 183, 352, and 465 cm −1 and these products were considered to be NdOCl [19]. As a reason to which measured peak positions became lower than reference values [19], since the Raman peak positions of RuO 2 shifted to lower wavenumber by residual stress [20][21][22], it was presumed that stress remained in the products even after a milling operation.…”

An Investigation of Synthesized Samarium Oxychloride in Molten LiCl-KCl

“…The solid-state Raman spectra report five symmetrical modes that are consistent with the previously published lanthanide oxychloride literature. 28,29 In Situ Electrochemistry and Spectroscopy CV experiments conducted on LiCl-KCl with SmCl 3 solvated at low concentrations may produce an additional anodic peak in a slightly more oxidative region than that associated with the traditional SmCl 3 redox couple. A sample CV that contains this additional anodic peak, indicated with an asterisk, is reported in Figure 7.…”