Multistep coupling of preexisting local ferroic distortions in PbTiO₃ above the Curie temperature

Temperature-dependent Raman spectroscopic analyses were performed for the prominent ferroelectric PbTiO₃ in the temperature range 130–1040 K, focusing particularly on its paraelectric state above the Curie temperature K. The temperature evolution of the anomalous Raman scattering reveals that not only local ferroic distortions persist at temperatures well above , but also there is a sequence of different coupling processes preceding the appearance of long-range ferroelectric order at . Our results indicate that, similar to relaxor ferroelectrics, the paraelectric phase of PbTiO₃ can be considered as an ergodic system of local ferroic distortions, which only on average appears to have cubic symmetry. (paper)