OS3-9
ELF を利用した機能性高充填密度ガラスの融液物性計測と機能発現メカニズムの解明
Physical property measurements of functional densely
packed oxide glass melts by using ELF for understanding
the atomistic origin of the functionality
増野敦信
Atsunobu MASUNO
京都大学大学院工学研究科，Graduate School of Engineering, Kyoto University

1. Introduction
Oxide glasses are generally considered to be substances in which network former oxides such as SiO2, B2O3,and P2O5 are the main components. The three-dimensional network is formed by random corner-sharing
connections between MO4 tetrahedra consisting of the cation Mn+ and oxide ion O2−. On the other hand, we
have recently succeeded in synthesizing a large number of unconventional glasses without any network
formation of the network former oxides by using a levitation technique (Figure 1)1,2). It was found that theseglasses exhibited outstanding physical properties such as a high refractive index, strong luminescence, highelastic modulus, large crack resistance, high dielectric constant, and large magneto-optic effect. These features
are derived from the high packing density caused by no network formation, however, the correlation between
the functionality and the atomic arrangement of the glasses is still unexplored. Furthermore, the elucidationof the structural origin for glass formation without network formation is one of the greatest challenges in glassscience because breaking the random corner-sharing networks should inevitably decrease glass forming
ability. Understanding glass formation process during cooling from a melt at an atomic or electronic level will
provide critical information to investigate the origin of the functionality and glass formation.

Figure 1. Structural models of conventional network glass and densely packed glass.
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2. Purpose of the project
The purpose of the project is to elucidate the structural and electronical mechanism for the functionality andglass formation of unconventional densely packed oxide glasses. Two approaches are planned to achieve thepurpose. One is to obtain thermophysical properties of a melt and supercooled liquid. The temperaturedependence of density and viscosity is required to evaluate glass formation and glass forming ability. The useof the electrostatic levitation furnace (ELF) on the ISS Kibo is essential to accurately measure the density andviscosity from above the melting point to lower temperatures with large supercooling3,4). This is because anelectrostatic levitation furnace on the ground, which requires a high vacuum to prevent electrical discharges,
cannot provide accurate data due to the loss of oxygen from the oxide melt. The ELF, which can levitate themelt in air, are the most suitable for the purpose of this project. The target compositions of the melts arealuminosilicate, rare-earth borate, rare-earth molybdate, aluminatantalate, and rare-earth silicate. These wereselected among many candidates of unconventional glasses prepared by a levitation technique because theglasses exhibit large crack-resistance, IR transparency, low thermal expansion, high elastic modulus, and highhardness. The data obtained will be compared with those of the melts that will become glass and those thatwill not, in order to quantify the glass-forming ability of the melts. Second approach is to perform structural
analysis of the melt. Raman scattering spectroscopy and X-ray and neutron diffraction experiments will bedone on the ground. Structural model that reproduces the experimental data will be prepared by moleculardynamics simulation. The reliability of the structural model can be greatly improved by using the densities
obtained from space experiments. The structural model is analyzed using various geometrical methods toextract characteristic atomic arrangements that are responsible for the functionality5,6). Combination ofthermophysical data and structural information of the unconventional oxide glass melts will provide
important clues on the issues of the atomistic origin of the functionality and glass formation. The results ofthis project will not only advance glass science, but also lead to the synthesis of new highly functional glasses
by optimizing the composition design and synthesis conditions in the future.

References
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A. Masuno: Structure of Densely Packed Oxide Glasses Prepared Using a Levitation Technique. J. Phys. Soc. Jpn, 91,(2022) 091003, DOI: 10.7566/JPSJ.91.091003.
A. Masuno: Functionalities in unconventional oxide glasses prepared using a levitation technique. J. Ceram. Soc. Jpn.,
130, (2022) 563, DOI: 10.2109/jcersj2.22073.
H. Tamaru et al.: Status of the Electrostatic Levitation Furnace (ELF) in the ISS-KIBO. Microgravity Sci. Technol., 30,(2018) 643, DOI: 10.1007/s12217-018-9631-8.
C. Koyama et al.: Very sharp diffraction peak in nonglass-forming liquid with the formation of distorted tetraclusters.
NPG Asia Mater., 12, (2020) 43, DOI: 10.1038/s41427-020-0220-0.
Y. Onodera et al.: Structure and properties of densified silica glass: characterizing the order within disorder. NPG
Asia Mater., 12, (2020) 85, DOI: 10.1038/s41427-020-00262-z.
S. Kohara: Probing order within disorder in oxide glasses and liquids by quantum beam diffraction. J. Ceram. Soc.
Jpn., 130, (2022) 531, DOI: 10.2109/jcersj2.22030.

© 2023 by the authors. Submitted for possible open access publication under theterms and conditions of the Creative Commons Attribution (CC BY) license(http://creativecommons.org/li censes/by/4.0/).
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