The role of random electric fields in relaxors

TL;DR

This paper investigates how static random electric fields influence the relaxor behavior in lead-oxide perovskites, revealing their role in phase stability and piezoelectric enhancement through comparative analysis of PZT and PMN-xPT.

Contribution

It demonstrates that quenched random electric fields are crucial for the relaxor phase and identifies the order parameter, highlighting structural differences linked to relaxor properties.

Findings

Random electric fields are essential for relaxor behavior.

Structural nanoscale differences correlate with piezoelectric enhancement.

Quenched fields establish the relaxor phase and define the order parameter.

Abstract

PbZr_{1-x}Ti_xO_3 (PZT) and Pb(Mg_{1/3}Nb_{2/3})_{1-x}Ti_xO_3 (PMN-$x$PT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter.