Raman Spectra of Molten NaBF4 to 606°C and 8% NaF-92% to 503°C

The Raman spectra of molten NaBF4 samples have been measured to 606°C, and spectra of samples of the eutectic mixture of 8 mole % NaF in NaBF4 were recorded to 503° using 4880-Å radiation from an argon-ion laser for excitation. The BF4− ion appeared to retain its tetrahedral symmetry under all the conditions studied in this investigation. The frequency of the ν1(a1) mode of BF4− decreased with increasing melt temperature, and weak, asymmetric features on the bands from the ν2(e) and ν4(f2) modes were observed in molten NaBF4 and in the melts with 8 mole % NaF. The interpretation of the Raman spectra of molten NaBF4 does not require postulating the existence of a quasilattice structure or phonons in the molten state.