Raman spectra of molten PbBr 2–NaBr and PbBr 2–KBr systems showed the strongly polarized bands at about 150 cm −1. These Raman bands were identified as the totally symmetric stretching vibration modes of tetrahedral species PbBr 4 2− by consulting with the result of neutron diffraction. The shape of Raman spectra did not change drastically with increasing concentration of alkali bromide or a rise of temperature. These results suggest that there existed PbBr 4 2− complex ions in the mixture melts, which might not form further clustering or networking.