Microheterogeneity and field-cooling effects on Pb[(Zn1∕3Nb2∕3)0.955Ti0.045]O3 single crystals probed by micro-Brillouin scattering

Microheterogeneity and field-cooling effects were investigated on Pb[(Zn1/3Nb2/3)0.955Ti0.045]O3 (PZN-4.5%PT) single crystals by using a high-resolution micro-Brillouin scattering. The temperature dependence of Brillouin shift showed a typical relaxor behavior with marked softening on approaching the diffuse phase transition, but also revealed a clear microareal variation in a rhombohedral phase below 150 °C which means a heterogeneity exists over a length scale of at least a few microns in PZN-4.5%PT. These two features seem to correlate with the coexistence of both micronsized domains and irregular nanosized domains, recently confirmed by high-resolution domain studies. This complex domain structure may make each microdomain represent different relaxor behaviors due to its own polar nanoregions and their dynamics. When the crystal was cooled under the electric field along the [001] direction from a cubic phase, two field-induced changes were observed in the Brillouin shift at around 143 °C and 106 °C. This observation is in good agreement with the dielectric measurements, meaning a medium-range ordered phase exists between short-range ordered and long-range order phases