Optical phonon modes and transmissivity in BaWO4 single crystal

Barium tungstate (BaWO4) single crystal has been grown using Czochralski technique. It belongs to the scheelite structure, forming the space group I41/a at room temperature and the primitive cell contains two molecular units. The polarized Raman spectra were recorded by a micro-Raman spectrophotometer system in the backscattering geometry. All the observed Raman modes were assigned. The Raman mode at 924 cm-1, which belongs to the totally symmetrical Ag optical modes, has the strongest intensity and its linewidth is 4.6 cm-1. The infrared active lattice vibrations have been studied, eight optical modes were observed and assigned. The ultraviolet absorption edge is at 256 nm and the optical transparency range is up to 2500 nm at room temperature. The energy gap Eg of this crystal was obtained from the optical transmission spectra. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)