Connections forged here in Corvallis have led to award-winning research from scientists across three continents. The collaboration, which included two Oregon State University doctoral alumni and a number of faculty, won the best paper award at Journal of the American Ceramic Society Awards Symposium.
The lead author, Nitish Kumar, a research associate at the School of Materials Science and Engineering at the University of New South Wales in Australia, received his doctorate in materials science from Oregon State in 2016.
He worked on the project with a fellow alumnus Eric Patterson, who now works as a materials research engineer at U.S. Naval Research Laboratory, as well as their former advisor, Dave Cann, professor of materials science, in addition to a number of other researchers.
“The research for this award took about 2 1/2 years, and receiving this award was an indication of our research being recognized and appreciated by the wider scientific community,” Kumar said. “I consider this award and the Graduate Research Assistant Award from College of Engineering at OSU as the two biggest awards I have received for my research.”
Their paper focuses on a relatively new class of materials – bismuth perovskites. A perovskite is a type of crystal structure commonly used in the design of electronic materials because of its inherent versatility. In particular, bismuth-based perovskites have been the focus of great interest by researchers as a potential replacement for more toxic materials such as lead. (Bismuth and lead are next to each other on the periodic table and are chemically similar.)
However, it has been a big challenge for materials researchers to develop materials that can compete with lead-based materials. The present work involves the development of new bismuth-based materials targeted for high-temperature capacitor applications.
“The materials we were working on showed some impressive properties,” Kumar said. “We looked at what further information we need to fully understand their behavior and what characterization tool can provide us with that information.”
The paper, titled “Defect mechanisms in BaTiO3-BiMO3 ceramics,” examines the role of point defects in this new class of materials. These “defects” are not flaws or cracks or something macroscopic. Rather, “point defects” refers to irregularities in the lattice on the atomic scale. The particular point defect central to the paper is an oxygen vacancy, an empty site in the crystal lattice where an oxygen ion is supposed to be.
Understanding the role of defects is an important research area in materials science, because defects often affect performance. For example, the failure of a capacitor or an ultrasonic transducer is often not due to a fundamental problem with the material. Rather, failure is caused by how the defects behave. (They may migrate over time, they may enable breakdown, they may initiate corrosion, etc.)
Once the defect chemistry of a material is understood, defects can also have beneficial effects. State-of-the-art ultrasonic transducers — used in biomedical applications, sonar, and non-destructive testing— rely on a piezoelectric material that has intentionally added defects. These defects are used to precisely engineer the properties of the transducer material to be highly sensitive to acoustic signals so a high-resolution image can be obtained.
While there has been progress in improving the materials properties of these new bismuth perovskites, the underlying defect chemistry of these systems is relatively unexplored. This National Science Foundation-funded project helped to develop a framework for understanding the interrelationship between point defects, processing conditions, and properties.
“These materials show great promise, and with improvements in the properties guided by the results of this project,” Cann said. “There are many potential applications that can be considered such as intermediate temperature solid oxide fuel cells, dual phase membranes, and other energy applications.”
Other collaborators on the project included Till Frömling from the Institute of Materials Science, Technische Universität Darmstadt; Edward P. Gorzkowski from the U.S. Naval Research Laboratory; Peter Eschbach from the College of Science at Oregon State University; Michael P. Muller and Roger A. De Souza from the Institute of Physical Chemistry, RWTH Aachen University; and Julie Tucker and Steve Reese from the College of Engineering at Oregon State University.
