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Study of local structural disorder in 0.6PbIn½Nb½O3-0.4PbMgNbO3 ceramics as revealed by 3D electron diffuse scattering
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
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.

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oorganisk kemi
Identifikatorer
URN: urn:nbn:se:su:diva-155270OAI: oai:DiVA.org:su-155270DiVA, id: diva2:1198308
Tillgänglig från: 2018-04-17 Skapad: 2018-04-17 Senast uppdaterad: 2018-05-02Bibliografiskt granskad
Ingår i avhandling
1. Local structure of perovskite ferroelectric ceramics as revealed by 3D electron diffuse scattering: A walk in between the Bragg peaks
Öppna denna publikation i ny flik eller fönster >>Local structure of perovskite ferroelectric ceramics as revealed by 3D electron diffuse scattering: A walk in between the Bragg peaks
2018 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: Department of materials and environmental chemistry, Stockholm University, 2018. s. 83
Nyckelord
Electron diffraction, Diffuse scattering, Local structural disorder, Perovskite, Ferroelectric ceramics, Transmission electron microscopy
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Oorganisk kemi
Forskningsämne
oorganisk kemi
Identifikatorer
urn:nbn:se:su:diva-155514 (URN)978-91-7797-302-7 (ISBN)978-91-7797-303-4 (ISBN)
Disputation
2018-06-14, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (Engelska)
Opponent
Handledare
Anmärkning

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript.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

Tillgänglig från: 2018-05-22 Skapad: 2018-04-23 Senast uppdaterad: 2020-05-08Bibliografiskt granskad

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