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Local structural mechanism for phase transition and ferroelectric polarization in the mixed oxide K0.5Na0.5NbO3

Kong, J. ; Liu, J. ; Marlton, F. ; Jørgensen, M. R.V. LU orcid and Pramanick, A. (2021) In Physical Review B 103(18).
Abstract

(KxNa1-x)NbO3 (KNN) and its solid solutions are considered as potential alternatives to traditional Pb-based piezoelectric materials. Recent investigations indicated that the local structure in KNN is much more complex than its long-range average structure. Here, we have undertaken a systematic investigation of the temperature-dependent evolution of local and average structures of KNN5 [(KxNa1-x)NbO3,x=0.5] using time of flight neutron scattering. Rietveld analysis of neutron diffraction patterns indicated that the average structure of KNN5 changes from monoclinic to tetragonal to cubic upon heating from 100 to 773 K. In contrast, analysis of neutron pair distribution function (PDF) indicated that the local structure stays monoclinic... (More)

(KxNa1-x)NbO3 (KNN) and its solid solutions are considered as potential alternatives to traditional Pb-based piezoelectric materials. Recent investigations indicated that the local structure in KNN is much more complex than its long-range average structure. Here, we have undertaken a systematic investigation of the temperature-dependent evolution of local and average structures of KNN5 [(KxNa1-x)NbO3,x=0.5] using time of flight neutron scattering. Rietveld analysis of neutron diffraction patterns indicated that the average structure of KNN5 changes from monoclinic to tetragonal to cubic upon heating from 100 to 773 K. In contrast, analysis of neutron pair distribution function (PDF) indicated that the local structure stays monoclinic within the above temperature range. Based on comparative analysis of local and average structures, it is proposed that the average structural phase transitions in KNN5 are partly derived from a local ordering of the polar units, which are correlated over a length of 10 15 Å. A clear indication of order-disorder type transition at 473 K is evident from the temperature-dependent PDF patterns. Additionally, based on local structural analysis, it is shown that large electrical polarization in KNN5 can be attributed to displacements of both A-site and B-site atoms. These structural insights may help in further optimization of electrical properties of Pb-free KNN piezoceramics.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review B
volume
103
issue
18
article number
184104
publisher
American Physical Society
external identifiers
  • scopus:85105997246
ISSN
2469-9950
DOI
10.1103/PhysRevB.103.184104
language
English
LU publication?
yes
id
a3eba2f9-4c13-4f30-b6e2-206159bef622
date added to LUP
2021-06-02 16:29:25
date last changed
2022-04-27 02:14:29
@article{a3eba2f9-4c13-4f30-b6e2-206159bef622,
  abstract     = {{<p>(KxNa1-x)NbO3 (KNN) and its solid solutions are considered as potential alternatives to traditional Pb-based piezoelectric materials. Recent investigations indicated that the local structure in KNN is much more complex than its long-range average structure. Here, we have undertaken a systematic investigation of the temperature-dependent evolution of local and average structures of KNN5 [(KxNa1-x)NbO3,x=0.5] using time of flight neutron scattering. Rietveld analysis of neutron diffraction patterns indicated that the average structure of KNN5 changes from monoclinic to tetragonal to cubic upon heating from 100 to 773 K. In contrast, analysis of neutron pair distribution function (PDF) indicated that the local structure stays monoclinic within the above temperature range. Based on comparative analysis of local and average structures, it is proposed that the average structural phase transitions in KNN5 are partly derived from a local ordering of the polar units, which are correlated over a length of 10 15 Å. A clear indication of order-disorder type transition at 473 K is evident from the temperature-dependent PDF patterns. Additionally, based on local structural analysis, it is shown that large electrical polarization in KNN5 can be attributed to displacements of both A-site and B-site atoms. These structural insights may help in further optimization of electrical properties of Pb-free KNN piezoceramics.</p>}},
  author       = {{Kong, J. and Liu, J. and Marlton, F. and Jørgensen, M. R.V. and Pramanick, A.}},
  issn         = {{2469-9950}},
  language     = {{eng}},
  month        = {{05}},
  number       = {{18}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review B}},
  title        = {{Local structural mechanism for phase transition and ferroelectric polarization in the mixed oxide K0.5Na0.5NbO3}},
  url          = {{http://dx.doi.org/10.1103/PhysRevB.103.184104}},
  doi          = {{10.1103/PhysRevB.103.184104}},
  volume       = {{103}},
  year         = {{2021}},
}