RAMAN-SPECTRUM OF NA2SO4 (PHASE-I AND PHASE-II)

The Raman spectra of high-temperature phases I and II of Na2SO4 crystals are reported. The phase I spectra indicate considerable disorder of sulfate tetrahedra even at 520 K, which is well below the melting temperature of 1157 K. Although the phase II spectra are complicated by multidomain effects, they show that the crystal c axis is common to phases I, II and III and that the as-yet unknown crystal structure of phase II is more closely related to the phase I hexagonal structure than the phase III orthorhombic structure. © 1990.