Functional Defects in Electroceramic Materials: Defect Engineering in Functional Ceramics
Sponsored by: ACerS Basic Science Division, ACerS Electronics Division
Program Organizers: Hui Xiong, Boise State University; Hua Zhou, Argonne National Laboratory; Yanhao Dong, Tsinghua University
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 9
Location: MS&T Virtual
Session Chair: Hua Zhou, Argonne National Laboratory; Yanhao Dong, MIT
8:00 AM Invited
Designing Optimal Defect Environments for High Ionic Conductivity and Surface Catalytic Reactions: Lane Martin1; 1University of California, Berkeley
Solid-oxide fuel/electrolyzer cells have stringent materials requirements related to defects – from electrolyte materials with low ohmic losses for oxygen vacancy migration to electrode materials with high oxygen-exchange rates. There is incomplete understanding, however, of the structure-property relationships that would enable the rational design of better materials. Here, using epitaxial thin-film growth, synchrotron radiation, impedance spectroscopy, and density-functional theory, the impact of manipulating the structure of model electrolyte (e.g., La0.9Sr0.1Ga0.95Mg0.05O3–δ) and electrode (e.g., La1-xSrxCo1-yFeyO3) materials on the evolution of defect-mediate ionic conductivity and surface oxygen-exchange reactions are studied. We will leverage thin-film strain and orientation to show how unit-cell volume and octahedral rotations can be tuned independently to produce high ionic conductivity and how in half-cell systems different orientations of electrodes [e.g., (100), (110), and (111)] provide completely different potentials for catalytic response, thus answering existing questions in the field.
8:30 AM Invited
Functional Defects by Design in Energy and Quantum Materials: Panchapakesan Ganesh1; 1Oak Ridge National Lab.
Defects determine and control properties of solid-state materials and to a large degree impart specific functionalities. E.g. kinetics of ionic transport fundamentally limits the performance, efficiency and operating conditions of almost all known renewable energy technologies; Creation and motion of defects can trigger concomitant ‘switchable’ metal-insulator, structural and magnetic phase-transitions showing coupled hysterics for Neuromorphic computing; Defects and interfaces can be used to modify topology of a solid leading to emergent new quantum-phases (say) for dissipationless, low-power quantum-transport, in topological quantum materials or can play the ugly role of quenching emergent topological properties. The challenge lies both in identifying relevant defects, accurately capturing their fundamental nature and influence on material functionality and using this knowledge to design improved materials, using state-of-the-art computational materials approaches, integrated with complimentary data-analytics as well as experimental capabilities. In this talk, I will attempt to highlight some of our recent activities in addressing this challenge.
9:00 AM Invited
Defects Engineering in Epitaxial Complex Oxides for Designed Functionality: Yingge Du1; 1Pacific Northwest National Laboratory
In this talk, I will present our recent effort in tuning the defect formation, migration, and segregation processes during materials synthesis and processing to achieve designed functional properties. For example, the existence of oxygen vacancies and vacancy ordering in as-grown SrCrO3−δ and SrFeO3−δ films are found to significantly change the structure and physical properties of the resultant films from those of their stoichiometric counterparts. Being able to visualize and control the structural evolution as a result of oxygen (vacancy) migration is critically important in designing fast ion conductors and memristor devices. Another example is Mg diffusion in Fe3O4(001), where we show that atomic scale defects (antiphase boundaries and vacancy ordering) in Fe3O4 directly impact the Mg diffusion kinetics and pathways.
9:30 AM Invited
Co-doping Strategies for Controlling Electrical Conductivity of BaTiO3 Ceramics: Elizabeth Dickey1; Gyung Hyun Ryu1; Preston Bowes1; Jonathon Baker1; Douglas Irving1; 1North Carolina State University
The degradation kinetics of important dielectric materials, such as BaTiO3, are highly influenced by the time-dependent electromigration of intrinsic lattice defects. The spatial redistribution of point defects also deteriorates ferroelectric properties by forming an internal bias field, leading to asymmetric polarization and strain hysteresis loops. Therefore, controlling point defect concentrations and mobilities is necessary to improve not only the initial material conductivity, but also the device lifetime and breakdown strength. This presentation will discuss co-doping design strategies to control defect concentrations and hence conductivity in BaTiO3. Experimental conductivity measurements are interpreted in the context of density functional theory (DFT)-based grand canonical point defect simulations. These studies provide fundamental insight into the ability of certain co-dopants to pin the Fermi level over broad oxygen activity ranges and improve the semi-insulating properties and degradation properties of BaTiO3. This research is sponsored by AFOSR under grant no. FA9550-19-1-0222.