Infrared reflectivity spectra of the superionic conductors Na β and β″-gallate are presented for the first time. The infrared active TO and the associated LO frequencies are determined from an analysis of the reflectivity data. The low frequency conductivity spectra exhibit very broad peaks at 85 and 80 cm-1 in the β and β″ phases, respectively. Unlike the case of Na β-alumina, these peaks are not at the same frequency as the Raman modes and are considerably more than an order of magnitude broader. This indicates that the low frequency Raman and infrared active modes in these materials are due to different normal modes of the system. © 1978.