Type of Document	Thesis
Author	Dyer, Michael
Author's Email Address	mdyer@eng.fsu.edu
URN	etd-04102006-132136
Title	Interfacial and Defect Structure in Nanoscale Ceria/Zirconia Superlattices
Degree	Master of Science
Department	Mechanical Engineering, Department of
Advisory Committee	Advisor Name Title Anter El-Azab Committee Member Chiang Shih Committee Member Namas Chandra Committee Member Peter N. Kalu Committee Member
Keywords	Computer Simulation Nanostructured Materials Interfaces
Date of Defense	2006-03-31
Availability	unrestricted
Abstract Ceria and zirconia ceramics are well known for their ability to conduct oxygen ions, making them useful in constructing devices such as oxygen sensors and solid-oxide fuel cells. Increasing the ionic conductivity of these materials is a major point of interest, because this increases the efficiency and decreases the operating temperature of such fuel cells. Recent experimental results have shown that superlattices of alternating CeO2 and ZrO2 thin films that are alloyed with Gd2O3 exhibit ionic conductivity that is superior to the individual monolithic materials. The enhanced ionic conductivity in these structures is attributed to the interfacial effects. Analytical modeling has shown that there are two possible mechanisms that lead to changes in the ionic conductivity: (a) an enhanced equilibrium concentration of oxygen vacancies in the layered structure arising as a part of the thermodynamic equilibrium across the interfaces, and (b) change in the defect formation energies and kinetic barriers due to interaction of defects with the epitaxial strain field in the heterogeneous system. The extent of this interaction is determined by the layer thickness and interfacial dislocation structure. Aiming to understand these mechanisms, a molecular dynamics (MD) study is performed to determine the interfacial and defect structures in pure and Gd-doped CeO2/ZrO2 superlattices, and the results are compared with the recent experimental observations.
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