Nanoscale compositional segregation and suppression of polar coupling in a relaxor ferroelectric

A number of relaxor ferroelectric ceramics have been demonstrated to possess a near stable value of relative permittivity over very wide temperature ranges. This cannot be explained by conventional theories of relaxors. One such system is based on the perovskite solid solution series: (1-x) (Ba0.8Ca...

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Bibliographic Details
Published inActa materialia Vol. 158; pp. 422 - 429
Main Authors Roncal-Herrero, Teresa, Harrington, John, Zeb, Aurang, Milne, Steven J., Brown, Andy P.
Format Journal Article
LanguageEnglish
Published Elsevier Ltd 01.10.2018
Subjects
Chemical segregation
Electron microscopy
Ferroelectric relaxor
Functional ceramics
Chemical segregation
Electron microscopy
Functional ceramics
Ferroelectric relaxor
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Summary:A number of relaxor ferroelectric ceramics have been demonstrated to possess a near stable value of relative permittivity over very wide temperature ranges. This cannot be explained by conventional theories of relaxors. One such system is based on the perovskite solid solution series: (1-x) (Ba0.8Ca0.2)TiO3-xBi(Mg0.5Ti0.5)O3, giving stable relative permittivity from 150 to 500 °C. We show by scanning transmission electron microscopy and electron energy loss spectroscopic elemental mapping that nanoscale compositional segregation occurs in the temperature stable relaxor composition (x = 0.55), with Ba/Ti clusters some 2–4 nm in extent, separated by Bi-rich regions of comparable size. This nanomosaic structure is consistent with phase separation into a ferroelectrically active BaTiO3 – type phase (Ba/Ti rich) and a weakly polar Bi/(Mg) rich perovskite solid solution. The possibility that nanophase segregation is the cause of weak dipole coupling and suppression of the dielectric relaxation peak is considered. [Display omitted]
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2018.07.053