High Elastic Moduli of a 54Al2O3-46Ta2O5 Glass Fabricated via Containerless Processing

Abstract

Glasses with high elastic moduli have been in demand for many years because the thickness of such glasses can be reduced while maintaining its strength. Moreover, thinner and lighter glasses are desired for the fabrication of windows in buildings and cars, cover glasses for smart-phones and substrates in Thin-Film Transistor (TFT) displays. In this work, we report a 54Al2O3-46Ta2O5 glass fabricated by aerodynamic levitation which possesses one of the highest elastic moduli and hardness for oxide glasses also displaying excellent optical properties. The glass was colorless and transparent in the visible region, and its refractive index nd was as high as 1.94. The measured Young’s modulus and Vickers hardness were 158.3 GPa and 9.1 GPa, respectively, which are comparable to the previously reported highest values for oxide glasses. Analysis made using 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy revealed the presence of a significantly large fraction of high-coordinated Al in addition to four-coordinated Al in the glass. The high elastic modulus and hardness are attributed to both the large cationic field strength of Ta5+ ions and the large dissociation energies per unit volume of Al2O3 and Ta2O5.

Crack-resistant Al2O3–SiO2 glasses

“…As a result, the glass with the highest Al 2 O 3 content ( x  = 60) with mullite composition shows the highest elastic moduli and Vickers hardness. These values are comparable to hard glasses, such as R 2 O 3 –SiO 2 –Al 2 O 3 or CaO–SiO 2 –Al 2 O 3 glasses, and are much larger than those of crack-resistant silicate or borosilicate glasses789101112131819202122232425.…”

“…In case of alkali–alkaline earth silicate glasses, it was found that glasses with more packed structures had higher values of hardness and the elastic modulus6. Al 2 O 3 – R 2 O 3 and Al 2 O 3 –SiO 2 – R 2 O 3 glasses ( R : Y, Sc, or Ta) are among the hardest oxide glasses ( H V up to 9.5 GPa) with high elastic moduli ( E up to 169 GPa)78910111213. This is attributed to their high atomic packing density and high dissociation energy unit volume of components.…”

Low phonon energies and wideband optical windows of La2O3-Ga2O3 glasses prepared using an aerodynamic levitation technique

“…This enables the suppression of heterogeneous nucleation from the container wall and promotes deep undercooling and vitrification of the melt. In recent years, Al 2 O 3 -1112131415, TiO 2 -1617181920, Nb 2 O 5 -212223, and WO 3 -based24 glasses without any network formers have been discovered using this method. These “unconventional” glasses showed outstanding dielectric, optical, and mechanical properties as a result of the specific glass compositions and structures.…”

Additive Effects of Rare-Earth Ions in Sodium Aluminoborate Glasses Using <sup>23</sup>Na and <sup>27</sup>Al Magic Angle Spinning Nuclear Magnetic Resonance

“…In such oxide glasses, three kinds of Al coordination exist: 4-coordinated [4] Al, 5-coordinated [5] Al, and 6-coordinated [6] Al, which can all be quantitatively measured by magic angle spinning nuclear magnetic resonance (MAS NMR) [3] [4]. Using structural analysis of aluminate glasses using MAS NMR, it has been clarified that their physical properties, such as fictive temperature, microhardness, elastic modulus, and refractive index, are closely related to their Al coordination [5] [6] [7] [8]. Therefore, it is important to control Al coordination in oxide glasses for adjustments of those physical properties.…”