Breaking of macroscopic centric symmetry in paraelectric phases of ferroelectric materials and implications for flexoelectricity

A centrosymmetric stress cannot induce a polar response in centric materials; piezoelectricity is, for example, possible only in non-centrosymmetric structures. An exception is metamaterials with shape asymmetry, which may be polarized by stress even when the material is centric. In this case the me...

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Published inNature materials Vol. 14; no. 2; pp. 224 - 229
Main Authors Biancoli, Alberto, Fancher, Chris M., Jones, Jacob L., Damjanovic, Dragan
Format Journal Article
LanguageEnglish
Published London Nature Publishing Group UK 01.02.2015
Nature Publishing Group
Subjects
639/301/119/996
Asymmetry
Biomaterials
Breaking
Condensed Matter Physics
Electricity
Ferroelectric materials
Ferroelectrics
High temperature
Inhomogeneity
Materials Science
Nanotechnology
Optical and Electronic Materials
Phases
Piezoelectricity
Strain
Stresses
Symmetry
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Summary:A centrosymmetric stress cannot induce a polar response in centric materials; piezoelectricity is, for example, possible only in non-centrosymmetric structures. An exception is metamaterials with shape asymmetry, which may be polarized by stress even when the material is centric. In this case the mechanism is flexoelectricity, which relates polarization to a strain gradient. The flexoelectric response scales inversely with size, thus a large effect is expected in nanoscale materials. Recent experiments in polycrystalline, centrosymmetric perovskites (for example, (Ba, Sr)TiO 3 ) have indicated values of flexoelectric coefficients that are orders of magnitude higher than theoretically predicted, promising practical applications based on bulk materials. We show that materials with unexpectedly large flexoelectric response exhibit breaking of the macroscopic centric symmetry through inhomogeneity induced by the high-temperature processing. The emerging electro-mechanical coupling is significant and may help to resolve the controversy surrounding the large apparent flexoelectric coefficients in this class of materials. The unexpectedly large flexoelectric response in ferroelectric perovskite materials is now shown to be induced by macroscopic symmetry breaking in paraelectric phases.
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ISSN:1476-1122
1476-4660
DOI:10.1038/nmat4139