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

TL;DR

This study uses Raman spectroscopy to analyze the internal lattice dynamics and structural transformations in Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_{3}$ and its PbTiO$_{3}$-doped variant across a broad temperature range, revealing persistent dynamic distortions and phase evolution.

Contribution

It applies a previously tested Raman scattering approach to new relaxor ferroelectrics, providing a detailed temperature-dependent picture of their lattice dynamics and phase transitions.

Findings

Persistent dynamic lattice distortions at high temperatures.

Development of polar nanoregions with cooling.

Distinct temperature behavior of the weak Raman line E.

Abstract

Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_{3}$ is one of the simplest representatives of the lead ferroelectric relaxors. Its solid solution with PbTiO$_{3}$, at concentrations 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 pure Pb(Zn$_{1/3}$Nb$_{2/3} $)O$_{3}$ crystal and a crystal containing 4.5% of PbTiO$_{3}$, measured in a broad temperature range from 1000 to 100 K. We propose a comprehensive picture of the temperature evolution of the lattice dynamics in these crystals and associated structural transformations. We show, that in PZN, like in PMN, short-lived dynamic lattice distortions exist even at the highest measured temperatures. With cooling down, these distortions develop in Fm$\bar{3}$m clusters and R3m polar nanoregions that are still capable of reorientational motion. From the Burns temperature T$_{d}$, this motion becomes progressively restricted. The freezing process starts at the temperature T$^{*}$ and continues down to T$_{d0}$. The major Raman lines in all these materials behave very similarly. However, the temperature behavior of a weak line E in each case is essentially different. Its splitting can serve as a measure of the order parameter of the system.