Glasses with Hyperordered Structures

Glass has been considered a disordered material. However, recent advances in the structural analyses of oxide glasses have shown a degree of “order in disorder” at various scales in their atomic arrangements. This chapter describes oxide glasses with “hyperordered structures,” expanding on “order in disorder” in amorphous materials. Some classical criteria for glass formation are briefly summarized to understand oxide glass. The criteria were constructed through structural insights into the atomic arrangements of oxide glasses from Zachariasen and Sun and have been widely accepted hitherto. Recent findings on characteristic atomic arrangements in various glass systems that have been shown by effective combinations of experiments and calculations are introduced. The structure of silica glass, including the size and distribution of voids in the network structure, can be controlled using temperature and pressure to improve optical transmission by decreasing Rayleigh scattering. The structural information obtained using the newly developed mathematical method, the persistent homology analysis, provides clues to understanding the hyperordered structural origin of the well-known mixed alkali effect observed in alkali-silicate glasses. Oxide glasses with few or no network formers, prepared using a levitation technique, are also among examples of hyperordered structures due to their characteristic glass structures with high packing density. Furthermore, the reduced atomic arrangement (RAA) method was introduced to visualize the hyperordered structures of amorphous In2O3–ZnO films. Finally, the slight displacement from the ordered atomic arrangement, deduced from the RAA method, is shown to be one of the possible viewpoints that induce a unified understanding of the hyperordered atomic arrangement of densely packed oxide glasses.