Parametrization of nonstoichiometric lithium niobate crystals with different states of defectivity

Abstract Quasi-elastic light scattering (QELS) and Raman scattering have been studied at 296 K in congruent lithium niobate (CLN) crystals with a different degree of defectiveness. The defectiveness degree has been detected due to acoustic Q-factor. A quantitative analysis of spectra has been carried out in the frequency range 0–70 cm−1 in samples with different Q-factor. The applied model considers a connection between low-frequency optical mode A1(TO) symmetry type with relaxing intrinsic energy. The model describes stoichiometry defects. Results of model calculations and experiments allows us to conclude that different types of defects play a substantial role in formation of dynamic central peak at a structure phase transition in CLN crystals.