Advancements in the understanding and synthesis of transition metal compounds have allowed materials engineers to design functional materials with a range of properties, such as ferroelectricity, non-linear optical activity, colossal magnetoresistance, and superconductivity. Conventional routes to tune and design functional materials includes chemical cation substitution and heterostructuring of oxide thin films. Anion engineering has recently been identified as another route to design mate- rials with targeted properties by coordinating anions of different size, charge, and electronegativity to the same transition metal cation. Because of the similar sizes of fluorine and nitrogen to oxygen, anion substitutions also adds additional design variables, such as anion order, that are absent in homoanionic (i.e. oxide) compounds. Heteroanionic materials design provides an opportunity to expand the chemical design space for functional materials and to realize enhanced or unanticipated electronic, optical, and magnetic phenomena though its complex structural space. However, an understanding of the crystal-chemistry principles that govern the structure and properties of heteroanionic materials are still in their infancy. In this dissertation, I utilize first principles calculations to explore the materials physics associated with anion engineering in oxyfluorides. Oxyfluorides are an intriguing class of heteroanionic materials due to their similarity to transition metal oxides and potential structural complexity from anion ordering. This work 1) adapts crystal-chemistry principles from homoanionic materials to heteroanionic materials and uses them to predict novel oxyfluorides, 2) investigates known mechanisms for ferroelectricity in bulk and thin film oxyfluorides and formulates new ones and, 3) evaluates the effect of anion (dis)order on the electronic states of oxyfluorides. My research advances our understanding of oxide-fluoride structures and their properties, motivating future experimental and materials design efforts on heteroanionic materials.

Creator

• Harada, Jaye Kimiko

DOI

• https://doi.org/10.21985/n2-dfmk-jg12

Subject

• Materials Science

Language

• en

Alternate Identifier

• etdadmin_upload_819002
• http://dissertations.umi.com/northwestern:15569

Keyword

• Oxyfluoride
• Materials Design
• Functional Properties
• Density Functional Theory

Date created

• 2021-01-01

Resource type

• Dissertation

Rights statement

• In Copyright