Acoustic phonon mode anomalies in lanthanum doped lead zirconate-titanate relaxor ferroelectric ceramics

Abstract

Lanthanum-doped lead zirconate titanate, PLZT-x/65/35 (x=8.0, 9.0, and 9.4), relaxor ferroelectric ceramics were investigated by the high resolution Brillouin light scattering spectroscopy in the temperature range from ∼870 down to ∼170 K. Broad anomalies were observed in the acoustic phonon mode velocity and related elastic stiffness coefficient showing minimum between ∼320-∼240 K. The deviation in the acoustic mode velocity from the high temperature linearity at the Burns temperature (TB ∼720 K) and presence of a broad central peak in the temperature range 200≤T≤540 K were attributed to the dynamics of polar nanoregions with randomly oriented local polarization appearing due to site and/or charge disorder at both A - and B -sites of the ABO3 perovskite lattice. The presence of a new temperature point Td (∼575 K) was conclusively established in PLZT-x/65/35 relaxor ceramics. © 2009 American Institute of Physics.