Direct observation of fast atomic diffusion along ceramics grain boundary: Revealing sintering mechanism and guidelines for grain boundary engineering

A research group from the University of Tokyo, in collaboration with Tohoku University and Nagoya University, revealed a fast dopant diffusion mechanism along grain boundaries (GBs) using atomic-resolution electron microscopy combined with theoretical calculations. Impurity doping significantly improves the properties of polycrystalline ceramics. So far, GBs have been considered as the fast diffusion pathways of dopants, but the atomistic mechanism of the fast GB diffusion remains unclear. In this study, the group successfully observed the atomistic diffusion process of each Hf atom along the α-Al₂O₃ GB, using time-resolved scanning transmission electron microscopy. In addition, the group performed large-scale molecular dynamics simulations using a machine-learning interatomic potential. Through the synergetic collaboration of experimental observations and theoretical calculations, the group revealed the novel GB diffusion mechanism via GB interstitial sites. These findings provide valuable guidelines for designing materials with advanced functionality such as fast ionic conduction along GBs.

Time-resolved STEM images of Hf diffusion within α-Al₂O₃ GB

(a)-(c) Hf jumps between Al sites. (d)-(f) Hf jumps via interstitial sites.

Papers

Journal: Nature Communications

Title: Direct observation of substitutional and interstitial dopant diffusion in oxide grain boundary

Authors: Toshihiro Futazuka, Ryo Ishikawa*, Tatsuya Yokoi, Katsuyuki Matsunaga, Naoya Shibata, Yuichi Ikuhara*

DOI: 10.1038/s41467-025-64798-w