Hypersonic frequency softening and relaxation in relaxor ferroelectric 0.8Pb(Zn1/3Nb2/3)O3–0.2PbTiO3

Brillouin scattering from relaxor ferroelectric 0.8Pb(Zn1/3Nb2/3)O3–0.2PbTiO3 has been measured in the 300–723 K temperature range. A sharp ferroelectric phase transition from cubic to tetragonal symmetry, associated with a phonon frequency dip and a Landau–Khalatnikov-like damping maximum, has been observed near 528 K. Evidence for a relaxation mode in the form of a broad Rayleigh wing, whose frequency is strongly temperature dependent above 528 K, is found. The relaxation time and frequency are evaluated based on the tunneling model and a modified-superparaelectric model, respectively.