Yuichi Ikuhara

Yuichi Ikuhara, University of Tokyo

Grain Boundary Atomic Structures and Their Dynamics in Ceramics

Abstract
Grain boundary (GB) properties in ceramics are known to be strongly influenced by factors such as misorientation angle and the orientation of the GB plane, but the exact effects of these factors have yet to be fully understood. Additionally, dopant segregation at GBs plays a crucial role in modifying these properties. In this study, we systematically fabricated various types of bicrystals from ceramics like such as Al2O3, ZrO2, SrTiO3, with and without dopants, in order to investigate their GB atomic structures. Using aberration-corrected scanning transmission electron microscopy (STEM), the atomic structures and chemical compositions of these GBs were thoroughly characterized. Beyond structural analysis, the dynamics of GBs, such as fracture and migration, were also studied using in-situ TEM straining experiments combined with nano-indentation and MEMS techniques. The results showed that GB fractures tend to occur along specific crystal planes, and dislocations were observed to emit from the crack front. Furthermore, we recently demonstrated that high-energy electron beam irradiation can precisely control GB migration in ceramics. This migration occurs via the cooperative shuffling of atoms in the GB ledges along defined routes, offering new insights into how GB migration proceeds. These findings provide valuable contributions to understanding various GB phenomena in ceramics.

Biography
Yuichi Ikuhara is Distinguished Research Professor of Institute of Engineering Innovation, School of Engineering at University of Tokyo. He graduated from Kyushu University with BS in 1983, and received Dr.Eng. from Department of Materials Sciences, Kyushu University in 1988. He then joined Japan Fine Ceramics Center (JFCC) as a researcher, and was the Division Manager at JFCC from 1993. In 1996, he joined University of Tokyo as an associate professor of Materials Sciences, and became a full professor in 2003. He was a visiting assistant professor at Case Western Reserve University from 1991 to 1993. His current research interest is interface and grain boundary science, advanced transmission electron microscopy, high-temperature ceramics, dislocation technology and so on. Dr.Ikuhara is author and coauthor of about 960 scientific original papers in this field, and has more than 410 invited talks at international and domestic conferences. He received “Japan Academy Prize” (2023), Medal with Purple Ribbon” from the Emperor of Japan (2016), “Humboldt Research Award” from Alexander von Humboldt Foundation (2010), “Honda Frontier Prize” from Honda Foundation (2010), “Sosman Lecture Award” (2015) and “Ross Coffin Purdy Award” (2008) from the American Ceramics Society and so on. He is a fellow of the American Ceramics Society (2011), member of World Ceramic Academy (2014) and a fellow of the Microscopy Society of America (2024). He holds a group leader position at JFCC and PI Professor of WPI-Advanced Institute for Materials Research (AIMR), Tohoku University concurrently.