Raman Spectroscopy Study of Molten M x AlF 3+ x —M' x AlF 3+ x Systems (M,M' = Li,Na,K)

Abstract

Raman spectra of (M, M')F–AlF₃ (M, M' =Li, Na, K) molten salts have been obtained at 1293 K. The intensity ratios between the bands that are characteristic of the different complexes are strongly affected by the ratio M/M', especially when one of the alkaline cations is Li⁺. Its presence together with another cation seems to produce an increase in the acidity of the melt. The result of the deconvolution of the spectra compares well with vapor pressure data from the literature, showing the same kind of deviation. A qualitative explanation is proposed, but a quantitative modeling has not been possible up to now, because there is a lack of thermodynamic data that would allow a comparison with the spectroscopic results.