Investigating structure and chemistry in functional ferroelectric ceramics via transmission electron microscopy

Abstract

This thesis is concerned with studying the structure and chemistry of ferroelectric materials on the microand nanoscale, to determine how such attributes contribute to the functional properties of the materials for use in device applications. The main technique used throughout is transmission electron microscopy, although the results are interspersed with data from other complementary techniques, which have been used to corroborate the findings by collaborators. There are two systems which are studied herein, each of which has a different motivation underpinning the research presented. The first system is a mixed oxide electroceramic, of composition 0.75Bi(Fe0.97Ti0.03)O3-0.25BaTiO3. This system is studied for its potential use in piezoelectric sensor and actuators as a replacement for lead-based materials, currently used in these devices. The search for such a replacement has been driven by the threat of EU regulations regarding the use of lead-based materials in devices, owing to its environmental toxicity. The second system is the improper ferroelectric, CsNbW2O9, which has been studied for its potential application in the field of domain wall nanoelectronics. This field has developed as a result of the discovery of conducting domain walls in certain ferroelectric systems. The flexibility of domain walls under externally applied fields, in tandem with their minute size, opens the door for a whole new design of miniaturised, reconfigurable electronics, in which electrical interconnects, or even devices themselves, are constructed from conducting domain walls. Although in the early stages of research, this may provide a viable route to continue device miniaturisation in accordance with Moore’s law; a problem which has received much attention as current technology approaches fundamental limits, which may only be surpassed with a new paradigm of electronics design.

Date of Award	Dec 2021
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Engineering & Physical Sciences Research Council
Supervisor	Ian MacLaren (Supervisor) & Marty Gregg (Supervisor)