Phase transitions in KLiSO4 and RbLiSO4+: An infrared spectroscopic investigation

Infrared spectroscopy shows the occurrence of a transition to a phase of lower symmetry on cooling KLiSO4 below 170K, but there appears to be no change in the point group symmetry of the SO4 2- ion across the C6 6−C4 3v transition around 200K. Infrared spectra characteristic of the various phases (I–V) of RbLiSO4 have been obtained. True monoclinic order in RbLiSO4 seems to be present only in the room-temperature phase (V). Bands due to the LiO4 units in both these solids have been studied through the phase transitions.