Analysis of infrared reflectivity in the presence of asymmetrical phonon lines.

The temperature dependence of the ir reflection spectrum (A(1)-type modes) of LiTaO(3) is reported from room temperature up to ~1300 K, that is, 400 K above the ferroelectric-paraelectric phase transition. Results for the isomorphic compound LiNbO(3) are also presented. Certain phonon resonance lines are found asymmetric. Several dielectric function models are discussed. Certain advantages of ir reflectivity spectroscopy are emphasized.