Optical Spectra of Gadolinium(III) Ions in Melts of Alkali Metal Fluorides

Abstract

Optical spectra of MF−GdF₃ (M = Li, Na, K, and Cs) and NaF−CsF−GdF₃ molten systems are presented. On the basis of spectral data, it has been determined that stable complex groups \(\rm{GdF}_{6}^{3-}\) are formed in these melts. In the molten LiF−GdF₃ system, the \(\rm{GdF}_{4}^-\) group, which decomposes over time, is found along with the \(\rm{GdF}_{6}^{3-}\) complex group. It has been suggested that the number of cations in the second coordination sphere of the \(\rm{GdF}_{6}^{3-}\) groups decreases from 14 to 13 when passing from the melts of LiF, NaF to KF, CsF.