The temperature dependence of the ir reflection spectrum (A1-type modes) of LiTaO3 is reported from room temperature up to ~1300 K, that is, 400 K above the ferroelectric-paraelectric phase transition. Results for the isomorphic compound LiNbO3 are also presented. Certain phonon resonance lines are found asymmetric. Several dielectric function models are discussed. Certain advantages of ir reflectivity spectroscopy are emphasized.
J. L. Servoin and F. Gervais, "Analysis of infrared reflectivity in the presence of asymmetrical phonon lines," Appl. Opt. 16, 2952-2956 (1977)