Hypersonic and dielectric properties of (PbZn1/3Nb2/3O3)0.915-(PbTiO3)0.085 single crystal

Both the longitudinal Brillouin backscattering spectra and dielectric permittivities along the [001] direction have been measured as a function of temperature for a relaxor ferroelectric single crystal (PbZn1/3Nb2/3O3)(0.915)-(PbTiO3)(0.085) (PZN-8.5%PT). A sharp ferroelectric phase transition (which is associated with a Landau-Khalatnikov-type phonon damping maximum) was observed near 450 K. As temperature deceases, a diffuse phase transition (which is associated with a broad acoustic phonon damping maximum) was detected near 355 K. This broad damping evolution is attributed to dynamic order-parameter fluctuations. In addition, the nature of the thermal hysteresis for the dielectric permittivity confirms that these transitions (near 355 and 450 K) are diffuse first order and first order, respectively. The frequency-dependent dielectric data epsilon(c)"(f,T) prove the existence of an electric dipolar relaxation process below 360 K. The activation energy, the Vogel-Fulcher temperature, and attempt frequency corresponding to this relaxation process are also calculated. (C) 2000 American Institute of Physics. [S0021-8979(00)05805-9].