Raman spectroscopic studies of yttrium (III) chloride–alkali metal chloride melts and of Cs2NaYCl6 and YCl3 solid compounds

The Raman spectra of molten YCl3–A Cl (A=Cs, K, Li) mixtures have been measured at different compositions and temperatures up to 890 °C. The Raman spectra of polycrystalline Cs2NaYCl6 and YCl3 were also measured from 25 °C to temperatures above melting. The factor group analysis of crystalline Cs2NaYCl6 was used to identify the three Raman active modes (ν1, ν2, ν5) of the YCl6−3 octahedra. For liquid mixtures rich in alkali halide, the predominant features of the spectra are characterized by a polarized and a depolarized band with frequencies near the ν1 and ν5 frequencies of the YCl6−3 octahedron and thus indicates the existence of such species in the melt. In melts containing above 25% YCl3 a new polarized band D appears in the spectra which shifts continuously and rapidly to higher energies with increasing YCl3 concentration. The frequency shift is attributed to a continuous distortion mechanism of the YCl6−3 octahedra by the neighboring yttrium ions. The continuous frequency shift of the D band and a comparison of the liquid and solid Raman spectra of yttrium chloride suggest the existence of lattice-type modes in these melts.