High-pressure Brillouin scattering of the single-crystal PbSc1/2Ta1/2O3 relaxor ferroelectric

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2013
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  • The effect of pressure on the acoustic modes and adiabatic elastic constants of the perovskite-type (ABO3) relaxor compound PbSc 1/2Ta1/2O3 have been studied by Brillouin spectroscopy at room temperature up to 9.2 GPa. It is shown that the elastic constants are very sensitive to the pressure-induced structural transformations that were established by diffraction and Raman scattering analysis. Changes in the evolution of the pseudocubic elastic constants c11 and c 44 occur at the two phase-transition pressures pc1 = 1.9 GPa and pc2 ∼ 5.5 GPa. Changes in evolution of c12 occur at the two characteristic pressures p1* = 1.2 GPa and p2* ∼ 3.0 GPa, which mark changes in the local structure that precede the corresponding phase transitions. The elastic anisotropy and the width of the transverse acoustic mode increase in the pressure range between pc1 and p c2 with a maximum near p2*. A strong decrease in the Cauchy parameter is observed at pressures above p 2*, which indicates an enhancement of the covalent character of chemical bonding. Increasing pressure gradually suppresses the central peak typical of the relaxor ergodic state, and the quasielastic scattering vanishes at a pressure slightly above p2*. © 2013 American Physical Society.
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