Navigating Complexity: Harnessing Ionic Defects for Tailored Oxide Properties

Speaker

Qiyang Lu

Department of Materials Science and Engineering, School of Engineering, Westlake University 

About This Talk

Ionic defects are critical to the properties of functional oxides, governing mixed ionic and electronic conductivity, surface kinetics and reactivity, as well as lattice expansion and dynamics. These properties underpin applications in energy (e.g., fuel cells, electrocatalysts) and information technologies (e.g., memristors, neuromorphic computing). 

In this talk, Westlake University’s Qiyang Lu covers three fronts of harnessing ionic defects for tailored oxide thin film properties. First, to accurately predict the electrochemical driving force needed to manipulate ionic defects for designed properties, constructing phase diagrams that correlate physical properties (conductivity, chemical diffusivity, lattice constant, etc.) with ionic defect concentration is essential. However, such tasks often require a large number of samples and can be susceptible to artifacts introduced by sample-to-sample variations. To address this challenge, the group developed a new electrochemical device that can introduce spatially graded ionic defect concentrations in a single oxide thin film sample. Combined with high-spatial-resolution characterization tools, this approach enables high-throughput construction of phase diagrams controlled by ionic defect concentration. 

Second, they explore the kinetics of ionic defect incorporation into transition metal oxides at solid–liquid interfaces, combining operando optical and electrochemical characterizations. Their findings reveal the coexistence of surface and bulk processes during ion intercalation. 

Finally, they develop a comprehensive theoretical framework to elucidate the role of ionic defects in oxide electrocatalysts for the oxygen evolution reaction (OER). Drawing on insights from high-temperature solid–gas interfaces, they demonstrate that the “chemical overpotential,” driven by varying ionic defect concentrations, is equally critical for OER at room-temperature solid–liquid interfaces. 

Collectively, this work provides a holistic understanding of both the “static” and “dynamic” effects of ionic defects in determining the properties and functionality of oxide thin films. 

About the Speaker

Qiyang Lu is an assistant professor in the Department of Materials Science and Engineering at Westlake University in Hangzhou, China. He received his bachelor’s degree from Tsinghua University and his PhD in materials science and engineering from MIT, where his dissertation received the department’s Best PhD Thesis Award. He conducted postdoctoral research at Stanford University with a joint fellowship at the Advanced Light Source, Lawrence Berkeley National Laboratory. 

Lu is the recipient of the Ross Coffin Purdy Award from the American Ceramic Society and was a finalist for the Young Scientist Award of the International Society for Solid State Ionics in 2024. His current research focuses on designing ionic defects in mixed electronic and ionic conducting oxide thin films for reversible solid-state electrochemical cells, electrocatalysts, and ionotronic devices. 

About the MSE Seminar Series

The Materials Science and Engineering (MSE) Seminar Series features distinguished speakers from leading institutions, offering a platform for sharing groundbreaking research, innovative ideas, and entrepreneurial experiences. Held multiple times each semester, these seminars bring global perspectives world to MIT’s materials research community, exposing students, faculty, and postdocs to cutting-edge concepts and valuable networking opportunities.