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Title: Coupling of emergent octahedral rotations to polarization in (K,Na)NbO 3 ferroelectrics

Abstract

Perovskite potassium sodium niobates, K 1-xNa xNbO 3, are promising lead-free piezoelectrics. Their dielectric and piezoelectric characteristics peak near x = 0.5, but the reasons for such property enhancement remain unclear. We addressed this uncertainty by analyzing changes in the local and average structures across the x = 0.5 composition, which have been determined using simultaneous Reverse Monte Carlo fitting of neutron and X-ray total-scattering data, potassium EXAFS, and diffuse-scattering patterns in electron diffraction. Within the A-sites, Na cations are found to be strongly off-centered along the polar axis as a result of oversized cube-octahedral cages determined by the larger K ions. These Na displacements promote off-centering of the neighboring Nb ions, so that the Curie temperature and spontaneous polarization remain largely unchanged with increasing x, despite the shrinking octahedral volumes. The enhancement of the properties near x = 0.5 is attributed to an abrupt increase in the magnitude and probability of the short-range ordered octahedral rotations, which resembles the pre-transition behavior. Lastly, these rotations reduce the bond tension around Na and effectively soften the short Na-O bond along the polar axis - an effect that is proposed to facilitate reorientation of the polarization as external electric field is applied.

Authors:
 [1];  [1]; ORCiD logo [2];  [3];  [1]; ORCiD logo [4];  [1]
  1. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  2. Diamond Light Source, Didcot (United Kingdom)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Argonne National Lab. (ANL), Lemont, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
OSTI Identifier:
1460084
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS

Citation Formats

Levin, I., Krayzman, V., Cibin, G., Tucker, M. G., Eremenko, M., Chapman, K., and Paul, R. L. Coupling of emergent octahedral rotations to polarization in (K,Na)NbO3 ferroelectrics. United States: N. p., 2017. Web. doi:10.1038/s41598-017-15937-x.
Levin, I., Krayzman, V., Cibin, G., Tucker, M. G., Eremenko, M., Chapman, K., & Paul, R. L. Coupling of emergent octahedral rotations to polarization in (K,Na)NbO3 ferroelectrics. United States. doi:10.1038/s41598-017-15937-x.
Levin, I., Krayzman, V., Cibin, G., Tucker, M. G., Eremenko, M., Chapman, K., and Paul, R. L. Wed . "Coupling of emergent octahedral rotations to polarization in (K,Na)NbO3 ferroelectrics". United States. doi:10.1038/s41598-017-15937-x. https://www.osti.gov/servlets/purl/1460084.
@article{osti_1460084,
title = {Coupling of emergent octahedral rotations to polarization in (K,Na)NbO3 ferroelectrics},
author = {Levin, I. and Krayzman, V. and Cibin, G. and Tucker, M. G. and Eremenko, M. and Chapman, K. and Paul, R. L.},
abstractNote = {Perovskite potassium sodium niobates, K1-xNaxNbO3, are promising lead-free piezoelectrics. Their dielectric and piezoelectric characteristics peak near x = 0.5, but the reasons for such property enhancement remain unclear. We addressed this uncertainty by analyzing changes in the local and average structures across the x = 0.5 composition, which have been determined using simultaneous Reverse Monte Carlo fitting of neutron and X-ray total-scattering data, potassium EXAFS, and diffuse-scattering patterns in electron diffraction. Within the A-sites, Na cations are found to be strongly off-centered along the polar axis as a result of oversized cube-octahedral cages determined by the larger K ions. These Na displacements promote off-centering of the neighboring Nb ions, so that the Curie temperature and spontaneous polarization remain largely unchanged with increasing x, despite the shrinking octahedral volumes. The enhancement of the properties near x = 0.5 is attributed to an abrupt increase in the magnitude and probability of the short-range ordered octahedral rotations, which resembles the pre-transition behavior. Lastly, these rotations reduce the bond tension around Na and effectively soften the short Na-O bond along the polar axis - an effect that is proposed to facilitate reorientation of the polarization as external electric field is applied.},
doi = {10.1038/s41598-017-15937-x},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {2017},
month = {11}
}

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Works referenced in this record:

Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides
journal, September 1976