Transmission Electron Microscopy Study of Domains in Ferroelectrics
type: CreativeWork
description: This thesis investigates domain dynamics in one of the most well-known ferroelectric materials – polycrystalline BaTiO3 ceramics, and one of today’s most promising ferroelectric materials for future device applications – mixed-phase BiFeO3 thin films. The investigations use primarily TEM techniques accompanied by relevant theory and AFM techniques. The study on polycrystalline BaTiO3 (FIB lamellae) aims to further understand the link between domains coupling across adjacent grains and to explore the domains’ re-ordering as a function of heating through TC. Two cases were explored: domains coupling across a single grain boundary, and a more complex case of domains within adjacent grains meeting around a junction (or pore). Analysis using martensite crystallography theory demonstrated that domains sharing a single grain boundary do on average arrange themselves in a compatible and stress-free manner. For the example of grains arranged around a junction, a computational example was created, given the complexity of the case. It was demonstrated that the relaxation of the out-of-plane constraint gives rise to an undetermined set of linear equations which can be solved for compatible domain wall orientations and volume fractions of domains, indicating that groups of adjacent grains can form stress-free domain patterns. STEM in-situ heating cycle experiments, heating and cooling through TC, showed that the re-configuration of the domain structure (domain density, favourable domain orientations and presence of domain bundles) was directly influenced by the rate and continuous/dis-continuous nature of the performed heating cycles. Furthermore, this material was explored with focus on the functionality of its positive temperature coefficient of resistivity (PTCR) effect. Aberration-corrected STEM and EELS revealed a grain boundary PbTiO3-like region (~10-15 nm), which was associated with an increased local polarisation in that region. The chemical and electronic heterogeneity…
abstract: This thesis investigates domain dynamics in one of the most well-known ferroelectric materials – polycrystalline BaTiO3 ceramics, and one of today’s most promising ferroelectric materials for future device applications – mixed-phase BiFeO3 thin films. The investigations use primarily TEM techniques accompanied by relevant theory and AFM techniques. The study on polycrystalline BaTiO3 (FIB lamellae) aims to further understand the link between domains coupling across adjacent grains and to explore the domains’ re-ordering as a function of heating through TC. Two cases were explored: domains coupling across a single grain boundary, and a more complex case of domains within adjacent grains meeting around a junction (or pore). Analysis using martensite crystallography theory demonstrated that domains sharing a single grain boundary do on average arrange themselves in a compatible and stress-free manner. For the example of grains arranged around a junction, a computational example was created, given the complexity of the case. It was demonstrated that the relaxation of the out-of-plane constraint gives rise to an undetermined set of linear equations which can be solved for compatible domain wall orientations and volume fractions of domains, indicating that groups of adjacent grains can form stress-free domain patterns. STEM in-situ heating cycle experiments, heating and cooling through TC, showed that the re-configuration of the domain structure (domain density, favourable domain orientations and presence of domain bundles) was directly influenced by the rate and continuous/dis-continuous nature of the performed heating cycles. Furthermore, this material was explored with focus on the functionality of its positive temperature coefficient of resistivity (PTCR) effect. Aberration-corrected STEM and EELS revealed a grain boundary PbTiO3-like region (~10-15 nm), which was associated with an increased local polarisation in that region. The chemical and electronic heterogeneity…
author: Holsgrove, Kristina
language: eng
date published: 2017
date modified: 2026-07-24T03:54:46Z
provider: Queen's University Belfast
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Queen's University Belfast