Oxide Ion Conduction Mechanisms in Bismuth Perovskites

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NON-TECHNICAL DESCRIPTION: Emerging applications in the broad area of energy systems require new materials that have high ionic conductivities, chemical and thermal stability, and are composed of environmentally benign and inexpensive materials. This project is focused on developing an understanding of the relationship between the oxygen conductivity of bismuth-containing ceramics and the local atomic structure that controls the mobility of oxygen. This research will involve the synthesis of a number of ceramic compounds, measurement of their ionic conductivity, and characterization of their local structure using neutrons and X-ray scattering. With improvements in the properties guided by these findings, there are many energy-related applications that can be considered such as intermediate temperature solid oxide fuel cells, which have great potential as a cost-effective, clean power source. The research in this four-year project adds valuable expertise in the development of new energy materials and forms the basis of two doctoral theses, one in chemistry and the other in materials science. In addition, the project incorporates a high-impact K-12 outreach activity by hosting two high school students into the laboratory as part of an existing program, the Summer Experience in Science and Engineering for Youth (SESEY) at Oregon State University (OSU). This project also explores commercialization activities through a professional development program called Lens of the Market (LoM) which is supported at OSU through an National Science Foundation Research Traineeship (NRT) award in Innovations in Graduate Education (IGE).TECHNICAL DETAILS: This project builds upon recent developments on the defect chemistry and structural analysis of bismuth perovskite materials with an aim to develop a fundamental understanding of the dominant ionic conduction mechanisms in two bismuth perovskite systems, sodium bismuth titanate (NBT) and barium titanate-bismuth zinc titanate (BT-BZT). Both of these material systems have recently been shown to exhibit ionic conductivity values comparable to yttria-stabilized zirconia at temperatures below 600 degrees C. The overarching objective of this project is to identify the unique local structural distortions in bismuth perovskites that enable high oxygen conductivities in these materials. The specific research activities include the following objectives: (i) to systematically synthesize and process NBT and BT-BZT-based ceramics to control the level of oxygen stoichiometry, (ii) to characterize the electronic properties of NBT and BT-BZT-based materials, with a focus on the ionic conductivity, and (iii) to characterize the local structure, average structure, and oxygen non-stoichiometry of NBT and BT-BZT-based materials, with the focus on how doping and processing conditions influence this behavior. A greater understanding of the oxide ion conduction mechanisms will help guide the development of new materials for emerging energy applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.