Acoustic phonon dynamics of Pb(Sc_1/2Ta_1/2)O₃ceramics studied by Brillouin scattering spectroscopy

Abstract

Brillouin spectra of highly-ordered Pb(Sc1/2Ta1/2)O3 (PST-O) and highly-disordered PST (PST-D) were measured over a wide temperature range. The frequency of the longitudinal acoustic (LA) phonon mode of PST-O showed a sharp anomaly corresponding to the sharp maxima of the dielectric permittivity, whereas that of PST-D exhibits a broad anomaly. The remarkable softening of LA phonon was observed below T* = 500 K, which indicates the occurrence of a piezoelectric coupling and/or electrostrictive coupling due to the appearance of non-centrosymmetric polar nanoregions below T*. The relaxation time of the LA phonon of PST-O shows a critical slowing down for order-disorder phase transition, while that of PST-D exhibits a stretched slowing down due to random electric fields related to B-site randomness.

Introduction to rheometry for researchers of ultrasonics

“…Figure 3 shows a schematic image of the light scattering configuration and the experimental setup of the ripplon light scattering spectroscopy system. The principle is almost the same as that of the Brillouin scattering, 19) however, the conservation of momentum holds only with respect to the horizontal direction because the system of the liquid surface does not have translational symmetry along the vertical direction. One of the most important problems in the field of the chemical physics of liquid surfaces in the 1990s was the observation of the formation process of the surface layer of surfactant molecules.…”