Dynamical Properties of (1-x)(Na_0.5Bi_0.5)TiO₃-xBaTiO₃ Single Crystals Studied by Broadband Inelastic Light Scattering

Abstract

Dynamical properties of (1-x)(Na_0.5Bi_0.5)TiO₃-xBaTiO₃ (x= 0.05, 0.08) are investigated by the broadband inelastic light scattering and the dielectric measurements. The dielectric constant shows a maximum at T_m (the maximum temperature of a dielectric constant) where rhombohedral and tetragonal phases coexist. A central peak (CP) is clearly observed around T_m by the inelastic light scattering measurements, and it indicates that the polarization relaxation plays a key role for the maximum of the dielectric constant. We consider that the broad one is attributed to the overdamped soft phonon, while the narrow one is related to the relaxation of the local polarizatio. We suggest two possible origins of the local polarization relaxation.