Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Local structure of perovskite ferroelectric ceramics as revealed by 3D electron diffuse scattering: A walk in between the Bragg peaks
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Local structural disorder in crystalline materials plays a crucial role in understanding their properties. The means to study structural disorder is diffuse scattering (DS). Even though DS was observed since the early days of X-ray diffraction the weak intensity and the sheer number of different kinds of disorder hindered the development of a unique solution strategy. However, the advent of X-ray and neutron synchrotron sources together with recent advances in automated electron diffraction techniques have unraveled a new world in between Bragg peaks where a wealth of information is available.

In this thesis electron diffraction is used to explore the different kinds of DS in three-dimensions, for several perovskite ferroelectric ceramics. Based on the information presented in the reconstructed 3D reciprocal space volumes, disordered atomic structures were proposed and verified by the calculated electron diffraction patterns. A complex structural model for the local disorder in 85Na0.5Bi0.5TiO3-10K0.5Bi0.5TiO3-5BaTiO3 piezoceramic was developed by analyzing the morphology and intensity of electron DS in 3D. Next, the influence of potassium-content on the octahedral-tilt disorder for three different piezoceramics was studied by a combination of dark-field imaging and electron diffraction. Further on, the temperature-dependence of electron DS for 95Na0.5Bi0.5TiO3-5BaTiO3 piezoceramic revealed a local structural phase transition that was correlated with the depolarization mechanism. Lastly, strong electron DS was recorded from a Pb-based relaxor and simulations of disordered atomic structures showed that the local structure resembles a dipolar glass state. These demonstrate that electron diffraction is a powerful tool for the study of local structural disorder in crystalline materials, especially for ceramics. The major advantage is that we are able to record single-crystal electron diffraction data from individual grains. Moreover, since we are analyzing a 3D reciprocal volume several orientations can be studied simultaneously and we are not limited to zero-Laue zones. Finally, the models for local structural disorder provided valuable insight into how macroscopic properties are influenced by local structural disorder, in addition to the average structure.

Place, publisher, year, edition, pages
Stockholm: Department of materials and environmental chemistry, Stockholm University , 2018. , p. 83
Keywords [en]
Electron diffraction, Diffuse scattering, Local structural disorder, Perovskite, Ferroelectric ceramics, Transmission electron microscopy
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-155514ISBN: 978-91-7797-302-7 (print)ISBN: 978-91-7797-303-4 (electronic)OAI: oai:DiVA.org:su-155514DiVA, id: diva2:1200148
Public defence
2018-06-14, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2018-05-22 Created: 2018-04-23 Last updated: 2020-05-08Bibliographically approved
List of papers
1. Local disorder in Na0.5Bi0.5TiO3-piezoceramic determined by 3D electron diffuse scattering
Open this publication in new window or tab >>Local disorder in Na0.5Bi0.5TiO3-piezoceramic determined by 3D electron diffuse scattering
2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 12519Article in journal (Refereed) Published
Abstract [en]

Local structural distortions in Na0.5Bi0.5TiO3-based solid solutions have been proved to play a crucial role in understanding and tuning their enhanced piezoelectric properties near the morphotropic phase boundary. In this work all local structural disorders in a lead-free ternary system, namely 85% Na0.5Bi0.5TiO3-10% Bi0.5K0.5TiO3-5% BaTiO3, were mapped in reciprocal space by 3D electron diffraction. Furthermore, a comprehensive model of the local disorder was developed by analysing the intensity and morphology of the observed weak diffuse scattering. We found that the studied ceramics consists of plate-like in-phase oxygen octahedral nanoscale domains randomly distributed in an antiphase tilted matrix. In addition, A-site chemical short-range order of Na/Bi and polar displacements contribute to different kinds of diffuse scattering. The proposed model explains all the observed diffraction features and offers insight into the ongoing controversy over the nature of local structural distortions in Na0.5Bi0.5TiO3-based solid solutions.

National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-147844 (URN)10.1038/s41598-017-12801-w (DOI)000412050100040 ()28970571 (PubMedID)
Available from: 2017-11-01 Created: 2017-11-01 Last updated: 2018-05-02Bibliographically approved
2. The influence of potassium content on octahedral-tilt disorder in Na0.5Bi0.5TiO3-solid solutions near morphotropic phase boundary
Open this publication in new window or tab >>The influence of potassium content on octahedral-tilt disorder in Na0.5Bi0.5TiO3-solid solutions near morphotropic phase boundary
2018 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 152, p. 49-54Article in journal (Refereed) Published
Abstract [en]

A semi-quantitative comparison of 3D electron diffraction data revealed structural differences at the nanoscale for three (95-x)Na0.5Bi0.5TiO3-xK0.5Bi0.5TiO3-5BaTiO3 solid solutions close to the morphotropic phase boundary, with x = 0, 5, 10. Using a novel rotation electron diffraction technique, diffuse scattering intensity was recorded in 3D as continuous rods along hk0.5 reciprocal-planes. By analyzing the different superstructure reflections and the intensity/morphology of diffuse scattering, a structural model of the local octahedral-tilt disorder for the different ceramics was developed. A good agreement was obtained between the experimental and simulated data with a model comprising of antiphase (aaa) and plate-like in-phase (a0a0c+) nanodomains.

Keywords
Electron scattering, Diffuse scattering, Transmission electron microscopy (TEM), Perovskite, Ferroelectric ceramics
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-155266 (URN)10.1016/j.scriptamat.2018.04.016 (DOI)000435051400012 ()
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-07-23Bibliographically approved
3. Investigation of local structural phase transitions in 95Na0.5Bi0.5TiO3-5BaTiO3 piezoceramics by mean of in-situ transmission electron microscopy
Open this publication in new window or tab >>Investigation of local structural phase transitions in 95Na0.5Bi0.5TiO3-5BaTiO3 piezoceramics by mean of in-situ transmission electron microscopy
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The temperature-dependence of superstructure reflections, diffuse scattering intensity and ferroelectric domains morphology for 95Na0.5Bi0.5TiO3-5BaTiO3 ceramic was investigated by in-situ transmission electron microscopy. A subtle local structural phase transition was observed around 110°C. This local phase transition is characterized by a transformation in the dominant octahedral-tilt system from antiphase to in-phase tilting and was correlated with the depolarization mechanism common in this type of materials. Simulations of octahedral-tilt disorder were developed at different temperatures which enabled us to provide a comprehensive structural model that explains the temperature-dependence of superstructure reflections and electron diffuse scattering intensity. This model revealed that plate-like in-phase nanodomains tilted about three orthogonal axes coexist with an antiphase tilted matrix, even at room temperature. With increasing temperature, the concentration of in-phase nanodomains is increased till a critical volume fraction is reached. We propose that these plate-like in-phase nanodomains are an inherent characteristic of NBT-based compounds and that the local phase transition observed around 110°C leads to a disruption in the long-range ferroelectric order and is responsible for the depolarization mechanism.

National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-155269 (URN)
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-05-02Bibliographically approved
4. Study of local structural disorder in 0.6PbIn½Nb½O3-0.4PbMgNbO3 ceramics as revealed by 3D electron diffuse scattering
Open this publication in new window or tab >>Study of local structural disorder in 0.6PbIn½Nb½O3-0.4PbMgNbO3 ceramics as revealed by 3D electron diffuse scattering
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The local structural disorder in 0.6PbIn½Nb½O3-0.4PbMgNbO3 ceramic was revealed by 3D electron diffraction. Rotation electron diffraction method was applied to reconstruct the 3D reciprocal space volume containing both diffuse scattering and Bragg reflections. The butterfly-shaped diffuse scattering in the vicinity of h00 type reflections and the ellipsoidal-shaped diffuse scattering in the vicinity of hk0 type reflections were detected. Moreover, sharp superstructure reflections and strong diffuse scattering sheets along <110>* directions were observed in thin-volume sections centered along several zone axes cut from the 3D reciprocal space volume. This indicates that the local structure deviates significantly from the average one. By analyzing the intensity and morphology of diffraction features in 3D a model of structural disorder was developed comprising of 1:1 chemical short-range order of B-site cations and local displacements of Pb atoms. The final local structure is more akin to a spin glass state and no polar nanoregions were observed. This model was able to explain all significant diffraction features observed in volume-sections centered along three different zone axes.

National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-155270 (URN)
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-05-02Bibliographically approved

Open Access in DiVA

Local structure of perovskite ferroelectric ceramics as revealed by 3D electron diffuse scattering(1524 kB)94 downloads
File information
File name FULLTEXT01.pdfFile size 1524 kBChecksum SHA-512
79418dd19a8faa5293ae3d2d20582f9215adddebfc3f8355474e4793f87b908533b430ed7ba0abbb50b5aac571af2057a151e46c7ba75a5c42d8bc274dc24232
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Neagu, Alexandra
By organisation
Department of Materials and Environmental Chemistry (MMK)
Inorganic Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 94 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 695 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf