Raman spectroscopy study of molten MxAlF3+x-M ' xAlF3+x systems (M, M ' = Li, Na, K)

Raman spertra of (M, M')F-AlF3 (M, M' = Li, Na, K) molten salts have been o btained at 1293 K;. The intensity ratios between the bands that are charact eristic 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 ration seems to produce an increase in the acidity of the melt . The result of the deconvolution of the spectra compares well with vapor p ressure data from the literature, showing the same kind of deviation. A qua litative explanation is proposed, but a quantitative modeling has not been possible up to now, because there is a lack of thermodynamic data that woul d allow a comparison with the spectroscopic results.