Persistence of ferroelectricity above the Curie temperature at the surface ofPb(Zn1/3Nb2/3)O3−12%PbTiO3

N Domingo,J Santiso,G Catalan,N Bagués

doi:10.1103/physrevb.91.094111

Abstract

Relaxor-based ferroelectrics have been known for decades to possess a relatively thick surface layer (``skin'') that is distinct from its interior. Yet while there is consensus about its existence, there are controversies about its symmetry, phase stability, and origin. In an attempt to clarify these issues, we have examined the surface layer of PZN-12%PT. While the bulk transitions from a ferroelastically twinned tetragonal ferroelectric state with in-plane polarization to a cubic paraphase at ${T}_{\mathrm{c}}=200{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, the skin layer shows a robust labyrinthine nanodomain structure with out-of-plane polarization that persists hundreds of degrees above the bulk Curie temperature. Cross-sectional transmission electron microscopy analysis shows that the resilience of the skin's polarization is correlated with a compositional imbalance: lead vacancies at the surface are charge-compensated by niobium enrichment; the excess of $\mathrm{N}{\mathrm{b}}^{5+}$---a small ion with ${d}^{0}$ orbital occupancy---stabilizes the ferroelectricity of the skin layer.

Highlights

Morphotropic phase boundary relaxors have been intensely studied since the discovery in 1997 of their giant electromechanical performance [1]
Relaxor-based ferroelectrics have been known for decades to possess a relatively thick surface layer (“skin”) that is distinct from its interior
Cross-sectional transmission electron microscopy analysis shows that the resilience of the skin’s polarization is correlated with a compositional imbalance: lead vacancies at the surface are charge-compensated by niobium enrichment; the excess of Nb5+—a small ion with d0 orbital occupancy—stabilizes the ferroelectricity of the skin layer

Summary

Introduction

Morphotropic phase boundary relaxors have been intensely studied since the discovery in 1997 of their giant electromechanical performance [1]. While the bulk transitions from a ferroelastically twinned tetragonal ferroelectric state with in-plane polarization to a cubic paraphase at Tc = 200 ◦C, the skin layer shows a robust labyrinthine nanodomain structure with out-of-plane polarization that persists hundreds of degrees above the bulk Curie temperature.

Results

Conclusion