Dielectric anomalies induced by different mechanisms in Pb(Fe1/2Nb1/2)1-xTixO3 single crystals

TL;DR

This study explores dielectric anomalies in Pb(Fe1/2Nb1/2)1-xTixO3 single crystals, revealing different mechanisms such as hopping conductivity and dipole glass behavior through temperature-dependent measurements and local structural analysis.

Contribution

It identifies and distinguishes two different dielectric mechanisms in the material, supported by local structural and spectroscopic evidence.

Findings

Two dielectric anomalies observed in sample A, only one in sample B

Hopping conductivity between Fe2+ and Fe3+ causes one anomaly

Dipole glass behavior accounts for the weak anomaly in sample A

Abstract

We investigated the dielectric properties of Pb(Fe1/2Nb1/2)1-xTixO3 single crystals below room temperature. Two dielectric anomalies were detected in sample A while only one was detected in sample B in the temperature range 90~300 K. A Debye-like relaxation with strong frequency dispersion was detected in both samples. The pre-edge XAFS suggests that this dielectric anomaly is induced by the hopping conductivity between Fe2+ and Fe3+. The EXAFS results give us a clear picture of the local structure of iron ions. The weak frequency dependent dielectric anomaly only observed in sample A is supposed to be due to the dipole glass behavior.