Discovery of a New Diffusion Mechanism in Ceramics grain boundary: Unveiling the Sintering Mechanism and Establishing a New Guideline for Grain Boundary Engineering

A research team from the University of Tokyo, in collaboration with Tohoku University, has uncovered a new mechanism governing the diffusion of atoms along crystal grain boundaries by combining atomic-resolution electron microscopy with theoretical calculations.

In ceramic sintering processes, various dopants are added to promote densification and to control the resulting microstructure. Although it has been known that these additive elements diffuse along grain boundaries during sintering, it has remained unclear which atomic sites within the grain boundary they traverse during the diffusion process.

Here, the team focused on the grain boundaries of Ti-doped α-Al₂O₃ and successfully elucidated the atomic pathways taken by Ti atoms during diffusion, as well as the associated structural changes occurring at the diffusion front. This was achieved through a combination of atomic-resolution scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy, enabling structural and compositional analysis at the atomic level.

The α-Al₂O₃ grain boundary initially exhibited an asymmetric atomic configuration; however, as Ti diffused and its concentration increased, the grain boundary structure was observed to transform into a symmetric configuration. This finding indicates that a grain boundary phase transformation occurs in association with Ti diffusion, and this interpretation was further validated by first-principles calculations.

These results provide new insight into the establishment of optimal sintering conditions and the prediction of microstructural evolution in ceramics, thereby offering important guidelines for future ceramic materials design.

Fig 1. New model of grain boundary diffusion accompanied by structural transformation found in this study.

Papers

Journal: Nature Communications

Title: Two-step grain boundary diffusion mechanism of a dopant accompanied by structural transformation

Authors: Chuchu Yang, Bin Feng*, Toshihiro Futazuka, Naoya Shibata, Yuichi Ikuhara*

DOI: 10.1038/s41467-025-65745-5