Vibrational spectra of ternary sulfides with the Th3P4 structure

Raman spectra have been measured on powders of a sequence of compounds ARE2S4 (A = Ca, Sr; RE = larger rare earths) with the Th3P4 structure. All nine theoretically allowed Raman modes were observed only in low temperature spectra. Effects of disorder on the cation sub-lattice appear as increased widths in most of the Raman lines. Specular infrared reflectance was measured on a hot-pressed specimen of SrNd2S4 from which a classical oscillator fit gave the transverse and longitudinal optic modes