Raman scattering by polaritons in tetragonal BaTiO 3

Abstract

Raman scattering spectra by polaritons of A 1 symmetry in tetragonal BaTiO 3 at room temperature are used to establish the q ≈ 0 TO phonon frequencies and to estimate the dielectric constant along the ferroelectric axis ϵ cs. Values of ϵ cs = 37 ± 5 and ϵ cs = 38 ± 6 are found from the LST relation and the polariton dispersion curves respectively. It is also found that the two broad bands centered at 270 cm -1 and 520 cm -1 correspond to TO phonons. Their widths are explained by large anharmonic couplings and a frequency dependent damping constant.