Temperature dependence of Raman scattering and anharmonic properties in LiNbO3

The temperature dependence of the Raman spectrum in LiNbO3 is investigated from 100 to 700 K. The various sources of asymmetry of Raman bands and artefacts are discussed before analyzing the temperature dependence of A(1) and E first-order phonon lines. The phonon frequency downshift and damping increase on heating are interpreted in terms of normal volume expansion and third- and fourth-order anharmonic potentials. Anharmonic contributions are highly anisotropic and mainly explain the temperature dependences of both frequency and damping of A(1) optical vibrational modes along the ferroelectric axis. Results are consistent with Caciuc et al. (Phys Rev B 61:8806, 2000) predictions.