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
Investigation of local structural phase transitions in 95Na0.5Bi0.5TiO3-5BaTiO3 piezoceramics by mean of in-situ transmission electron microscopy
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
(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: urn:nbn:se:su:diva-155269OAI: oai:DiVA.org:su-155269DiVA, id: diva2:1198301
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-05-02Bibliographically approved
In thesis
1. Local structure of perovskite ferroelectric ceramics as revealed by 3D electron diffuse scattering: A walk in between the Bragg peaks
Open this publication in new window or tab >>Local structure of perovskite ferroelectric ceramics as revealed by 3D electron diffuse scattering: A walk in between the Bragg peaks
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
Keyword
Electron diffraction, Diffuse scattering, Local structural disorder, Perovskite, Ferroelectric ceramics, Transmission electron microscopy
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-155514 (URN)978-91-7797-302-7 (ISBN)978-91-7797-303-4 (ISBN)
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: 2018-05-23Bibliographically approved

Open Access in DiVA

No full text in DiVA

Search in DiVA

By author/editor
Neagu, AlexandraTai, Cheuk-Wai
By organisation
Department of Materials and Environmental Chemistry (MMK)
Chemical Sciences

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 17 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