A research group of Professor Takumi Fujiwara and Assistant Professor Yoshihiro Takahashi at Department of Applied Physics, Graduate School of Engineering, Tohoku University in collaboration with Minoru Osada, Senior Researcher, at National Institute for Materials Science has succeeded in elucidation of a precirsive stage of crystallization in oxide glass.

Since a disordered material―oxide glass without periodicity/regularity― possesses a high transparency and is able to form into any shapes, it has been a popular material in ordinary lives, and an advanced material for such as optical fiber. Optical fiber-type devices have recently been developed by means of local crystallization in order to provide special properties, which are essentially absent from glass materials, to the fiber-type device as the research group has succeeded previously, and thus glass crystallization has gathered attention as a method for high functionalization in the glass material. However, medium-range structure (a few nanometers) that is an origin of crystallization has been difficult to determine because of its random structure, and its relation to crystallization has not been clarified.

In this study, the research group has succeeded in revealing the precursive stage of crystallization by examining a unique spectroscopic feature so-called “boson peak”. It was found that an inhomogeneous region at nanometric scale in glasses produces crystal nucleus (embryo) in the early crystallization process, that is precursive stage. In addition, the results means that type of crystallization and number of nuclei has already decided at the stage of glass formation. These results also predict that a method providing structural modulation during glass formation, and/or laser-induced crystallization technique which would cause a mutation in the glass/crystal transition process are effective to control crystallization of oxide glass. Although exploitation of new composition/combination of elements has been a main way to develop the functional glass up to now, this study helps creation of innovative guidance for artificial nanostructure control in oxide glass.

The research results have been published on “Physical Review B” on June 23, 2009, and the research paper has been selected as Virtual Journal of Nanoscale Science & Technology by American Physical Society (APS) on July 6, 2009 issue.

[Contact]
Professor Takumi Fujiwara
Department of Applied Physics, Tohoku University
E-mail: fujiwara@laser.apph.tohoku.ac.jp