Ground State of Relaxor Ferroelectric $Pb(Zn_{1/3}Nb_{2/3})O_3$

TL;DR

This study reveals that the bulk of Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_3$ (PZN) does not exhibit the previously assumed rhombohedral symmetry at room temperature, instead showing a new phase with nearly cubic symmetry and slight tetragonal distortion, while the surface and field-induced states differ.

Contribution

The paper provides the first direct high-energy x-ray diffraction evidence that bulk PZN has a new phase (X) with nearly cubic symmetry, challenging prior assumptions of rhombohedral bulk structure.

Findings

Bulk PZN has a new phase (X) with nearly cubic symmetry.

Surface state of PZN shows rhombohedral phase.

Electric-field poling induces a rhombohedral phase at room temperature.

Abstract

High energy x-ray diffraction measurements on Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_3$ (PZN) single crystals show that the system does not have a rhombohedral symmetry at room temperature as previously believed. The new phase (X) in the bulk of the crystal gives Bragg peaks similar to that of a nearly cubic lattice with a slight tetragonal distortion. The Bragg profile remains sharp with no evidence of size broadening due to the polar micro crystals (MC). However, in our preliminary studies of the skin, we have found the expected rhombohedral (R) phase as a surface state. On the other hand, studies on an electric-field poled PZN single crystal clearly indicate a rhombohedral phase at room temperature.