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Ordering Is Required for Glass-Forming Liquids -Complete clarification of atomic and electronic structures of extremely ‘fragile’ liquid at 2800 ℃- (Press Release)

Release Date
18 Dec, 2014
  • BL04B2 (High Energy X-ray Diffraction)
  • BL08W (High Energy Inelastic Scattering)

Japan Synchrotron Radiation Research Institute (JASRI)
Japan Advanced Institute of Science and Technology (JAIST)
Japan Aerospace Exploration Agency (JAXA)
Gakushuin University
The University of Tokyo
Yamagata University

An international joint research team examined the atomic and electronic structures of a non-glass-forming liquid and clarified, for the first time in the world, that the liquid is extremely ‘fragile’ because of its highly disordered atomic and electronic structures and hence cannot form a glass. The team consisted of researchers from JASRI, JAIST, Tampere University of Technology in Finland, JAXA, Gakushuin University, the University of Tokyo, and Yamagata University. These achievements were obtained through experiments using high-brilliance high-energy synchrotron radiation X-rays at SPring-8*1 and large-scale simulation using supercomputers at the IT Center for Science Ltd., in Finland, Forschungszentrum Jülich in Germany, and at JAIST.

In general, glass is fabricated by melting a raw material at a high temperature and rapidly cooling the melt*2(liquid); however, not all materials can form a glass. The existence of a difference between the atomic structure of glass-forming liquids and that of non-glass-forming liquids has long been pointed out but has been difficult to clarify at the atomistic and electronic levels. Thus, the difference has remained a major mystery in the structural science of glass even in the 21st century.

To solve the mystery, the international joint research team focused on zirconium dioxide (ZrO2), a non-glass-forming material, and analyzed the structure of its liquid. ZrO2 has a particularly high melting point (2715 °C) among oxides and is difficult to melt; hence, conventional structure analysis methods cannot be used for ZrO2. In this study, the research team developed an instrument by combining the containerless gas levitation method*3 with the SPring-8 high-energy X-ray diffraction*4beamline and succeeded in the structural analysis of a ZrO2 liquid at an ultrahigh temperature of 2800 °C. By conducting large-scale theoretical calculations using supercomputers, the research team found that a specific peak commonly observed for glass-forming liquids does not appear in the diffraction pattern of the ZrO2 liquid. It was also found that the atomic configuration of structural units comprising zirconium and oxygen atoms becomes disordered in the liquid, causing electrons to move easily and that the lifetime of Zr-O bonds is only ~200 fs (1 fs = 10−15 s). The research team concluded that non-glass-forming liquids are disordered and so-called extremely ‘fragile’ liquids*5; namely, ordering is required for glass-forming liquids.

The discovery in this study relates the atomic and electronic structures of liquids with their glass-forming ability and solves one of the major mysteries in the structural science of glass. In addition, the atomistic- and electronic-level understanding of the liquid obtained in this study will become a key finding leading to the development of innovative materials such as ultrahigh-refractive-index glass and novel ceramics.

The research team was led by Shinji Kohara, a senior scientist at JASRI, and the achievements of this study were published online in the British scientific journal Nature Communications on 18 December 2014.

Article title:"Atomic and electronic structures of an extremely fragile liquid"
Authors:  S. Kohara, J. Akola, L. Patrikeev, M. Ropo, K. Ohara, M. Itou, A. Fujiwara, J. Yahiro, J. T. Okada, T. Ishikawa, A. Mizuno, A. Masuno, Y. Watanabe, T. Usuki
Journal title:Nature Communications
Publication date: 18 December 2014 (JST)
doi: 10.1038/ncomms6892


Fig.1 Schematic of containerless gas levitation system installed at SPring-8

A sample is heated and melted by a CO2 gas laser, levitated by a gas ejected from a conical nozzle, and irradiated with high-energy synchrotron radiation X-rays in the diffraction experiment. The upper left figure shows a photograph of the levitated high-temperature oxide melt.

Fig.2 Diffraction data of ZrO2 and silica (SiO2) liquids obtained by high-energy synchrotron radiation X-ray diffraction experiment at 2800°C at SPring-8 and large-scale first-principles molecular dynamics calculations


Fig.3 Atomic structures and schematic illustrations of (a) SiO2 crystal, (b) SiO2 liquid, and (c) ZrO2 liquid derived from large-scale density functional - molecular dynamics simulations (1 Å = 0.1 nm)

※1 SPring-8

SPring-8 (Harima Science Park, Hyogo, Japan) is a synchrotron radiation facility that provides the world's highest brilliance radiation. It’s owned by Riken and run by JASRI. The name "SPring-8" is from "Super Photon ring-8 GeV". Synchrotron radiation is a electromagnetic wave radiated when charged particles are forced to bend in magnetic fields. Synchrotron radiation from SPring-8 is widely used for the studies of nano-technology, bio-technology and industrial purposes.

※2 Melt
A melt is a synonym for a liquid. In particular, metallic and oxide liquids with high melting points are referred to as melts.

※3 Containerless gas levitation method (see Fig. 1)
An inert gas (e.g., Ar, N2) is blown from a conical nozzle to a sample upward in the vertical direction to levitate the sample without using a container. The sample is irradiated with a CO2 laser that can easily achieve a high temperature exceeding 2000°C. In this method, there is no risk of the melt being contaminated with the dissolved materials of the container and the liquid state is maintained (supercooled liquid state) at temperatures even below the melting point because of the absence of a heterogeneous interface between the melt and the container (crystal). The absence of the interface also prevents the formation of nuclei for the crystallization of the liquid, enabling the glass formation of materials with a low glass-forming ability.

※4 High-energy X-ray diffraction
When a material with an ordered atomic configuration is irradiated with X-rays as electromagnetic waves, the waves scattered at each atom interfere with each other, causing a strong diffraction wave (diffracted X-ray) to propagate in a specific direction. This phenomenon is called X-ray diffraction and can be used to analyze the atomic arrangement in materials. SPring-8 can generate high-energy X-rays with a high transmittance, which enables high-energy X-ray diffraction.

※5 Fragile liquid
A “fragile liquid” is a liquid that is difficult to form a glass and its opposite is a “strong liquid”. These terms were introduced in Science in 1995 by Austen Angell, who examined the temperature dependence of the viscosity of liquids from high temperature to the glass transition temperature. He defined liquids whose viscosity rapidly changes with decreasing temperature during solidification as fragile liquids and liquids whose viscosity moderately changes (or is originally high) as strong liquids. Since then, these concepts have been widely used as indices of the glass forming ability of liquids.

For more information, please contact:
Senior scientist Shinji Kohara 
(Research and Utilization Division, JASRI)
(Visiting professor at School of Materials Science, JAIST)

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