Temperature dependence of Raman scattering and anharmonic properties in LiNbO_3

The temperature dependence of the Raman spectrum in LiNbO \(_3\) 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.