Raman spectroscopy study of internal dynamics in Pb(Zn_{1/3}Nb_{2/3})O_{3} and 95.55%Pb(Zn_{1/3}Nb_{2/3})O_{3}-4.5%PbTiO_{3} crystals

摘要

Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_{3}$ is one of the simplest representatives of thelead ferroelectric relaxors. Its solid solution with PbTiO$_{3}$, atconcentrations near the morphotropic phase boundary, is especially important.In this paper, we apply the tested earlier on Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$approach, to analyze the light scattering from both, nominally purePb(Zn$_{1/3}$Nb$_{2/3} $)O$_{3}$ crystal and a crystal containing 4.5% ofPbTiO$_{3}$, measured in a broad temperature range from 1000 to 100 K. Wepropose a comprehensive picture of the temperature evolution of the latticedynamics in these crystals and associated structural transformations. We show,that in PZN, like in PMN, short-lived dynamic lattice distortions exist even atthe highest measured temperatures. With cooling down, these distortions developin Fm$\bar{3}$m clusters and R3m polar nanoregions that are still capable ofreorientational motion. From the Burns temperature T$_{d}$, this motion becomesprogressively restricted. The freezing process starts at the temperatureT$^{*}$ and continues down to T$_{d0}$. The major Raman lines in all thesematerials behave very similarly. However, the temperature behavior of a weakline E in each case is essentially different. Its splitting can serve as ameasure of the order parameter of the system.