Understanding thermal metamorphosis in oxide glass

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Gaining insight into the molecular structure and physical properties of glass

Scientists at Kyoto University Research Reactor Institute (KURRI), National Institute for Materials Science (NIMS), National Institute of Advanced Industrial Science and Technology (AIST), Ritsumeikan University, and Chiba University have gained new insight into the structure of glass, providing crucial information for the design of novel materials.

Glass has many beneficial characteristics: it is transparent and rigid, yet at the same time malleable, easily processed, and chemically as well as thermally stable, properties that make it an indispensable material in our everyday lives.

It is also a well-studied material among scientists. Understanding the arrangement of atoms in glass is a puzzling topic, because the molecules are oriented at random. However, order within disorder seems to be the origin of its various beneficial properties.

Phosphate glass is commonly considered for practical applications because of its durability. Due to its unique physical and structural properties, it has significant potential for application in other areas as well. While it is well known that the network structure in glass affects its physical properties, this has not been well understood on a systematic basis. The same is observed in the PO 4 and ZnO x network of phosphate glass. Therefore, understanding the network structure of a phosphate glass system is one of the most important unresolved issues facing glass science.

In a recent Nature Communications paper, the research group discovered for the first time that the thermal expansion coefficient of ZnO-P 2 O 5 glass is eccentrically different from conventional varieties.

To uncover why, the researchers performed modelling based on experimental data and found that the molecular structure is largely taken on by Zn-O polyhedral units in a ZnO rich composition, while conventional wisdom would imply the interconnection of PO 4 tetrahedra. They were surprised to find that the network structure drastically changes with only a small difference in the composition of the glass.

This finding, based on structure modelling at the atomic scale, clarifies the connection between glass structure and observable physical properties. The researchers are confident that further modelling involving multiple data sets will provide crucial information for novel material design in the future.

The changing network structure of phosphate glass and zinc glass (Kyoto University / Yohei Onodera)

Paper Information

【DOI】 https://doi.org/10.1038/ncomms15449

【KURENAI ACCESS URL】 http://hdl.handle.net/2433/225118

Yohei Onodera, Shinji Kohara, Hirokazu Masai, Akitoshi Koreeda, Shun Okamura & Takahiro Ohkubo (2017). Formation of metallic cation-oxygen network for anomalous thermal expansion coefficients in binary phosphate glass. Nature Communications, 8, 15449.