Abstract :
The Raman scattering spectra of lithium tantalate crystals with different compositions were investigated. The comparison of the Raman data obtained for the congruent and the near-stoichiometric crystals reveals some differences in the shape and the number of Raman peaks, which lead to a new assignment of the long-wavelength optical phonons. And quantitative relationships between the linewidth of Raman peaks (142 cm−1 for E-phonon and 861 cm−1 for A1-phonon) and the crystal composition were firstly presented. Two local Raman lines, 278 and 750 cm−1, were found for the congruent crystals and attributed to the intrinsic defects, Li vacancy and anti-site Ta ion, respectively.
