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Press Releases

DATE2025.01.31 #Press Releases

Fast interconversion between two phases at crystal surfaces

-Discovery of a bidirectional phase transition phenomenon-

Summary

A research group led by Project Professor Eiichi Nakamura of the School of Science at The University of Tokyo, in collaboration with Professor Minoru Hanaya of the Graduate School of Science and Technology at Gunma University, has used an atomic-resolution transmission electron microscope (AR-TEM) to observe the growth process of nano-sized aluminum oxide crystals in the range of milliseconds to 60 seconds. As a result, they discovered a phenomenon in which an irregular crystal with a two-dimensional projected area of a few nm² grows into a crystal with an area of about 10 nm², moving back and forth between two crystal polymorphs, η-type and θ-type, at a high speed. It is noteworthy that macroscopically, the θ-type is the stable phase, and it was thought to change unidirectionally toward this phase. At the nanosize, the energy difference between the two phases shrinks under the influence of surface energy, and it is clear that such an equilibrium state occurs. This achievement is expected to contribute to the rationalization of crystal polymorphism control in the design and manufacture of materials, pharmaceuticals, and agrochemicals.


Figure:Verification of crystal melting process using nanoparticles as a model

Project Professor Eiichi Nakamura and Project Associate Professor Takayuki Nakamuro of the Department of Chemistry contributed in this research achievement.

links: Gunma University

Journal

Journal name
Science
Title of paper