MEMS Seminar: Ruijuan Xu, Manipulating Phase Transitions in Lead-Free Ferroelectric Heterostructures and Membranes"

Thomas Lord Department of Mechanical Engineering & Materials Science (MEMS), Fall 2025 Speaker Series welcomes Dr. Ruijuan Xu, from North Carolina State University, to deliver a talk entitled, "Manipulating phase transitions in lead-free ferroelectric heterostructures and membranes." Abstract: Complex oxides are fascinating materials that exhibit a rich spectrum of electrical, magnetic, optical, and thermal properties. Recent advances in atomic-scale epitaxy have enabled the creation of high-quality oxide heterostructures and freestanding membranes, opening new pathways to explore and manipulate emergent phase transitions and functionalities. In this presentation, I will use sodium niobates as a model system to demonstrate how external stimuli such as strain, electric fields, and size effects can be harnessed to induce novel ferroic orders with enhanced ferroelectric and dielectric responses. I will discuss a strain-induced emergent phase boundary in sodium niobate heterostructures, where competing structural phases yield multi-state switching and enhanced dielectric susceptibility and tunability. I will also highlight an intrinsic, size-driven antiferroelectric-to-ferroelectric transition in freestanding sodium niobate membranes. Biography: Dr. Ruijuan Xu is an Assistant Professor of Materials Science and Engineering at North Carolina State University. Ruijuan received her B.E. from Zhejiang University, her M.S. from the University of Illinois at Urbana-Champaign, and her Ph.D. from the University of California, Berkeley, all in Materials Science and Engineering. Before joining NC State, she was a GLAM Postdoctoral Fellow in the Department of Applied Physics at Stanford University and SLAC National Laboratory. Ruijuan's current research focuses on the atomic-scale design and manipulation of novel functional properties and exotic phenomena in ferroic oxide thin films, heterostructures, and membranes. She has been recognized by several recent awards including 2025 NSF CAREER Award, 2025 Scialog Fellow in Quantum Matter and Information, and 2024 iWOE Prize in Oxide Electronics for Excellence in Research.