Sophisticated electron spectroscopy and computer simulations have been used by a team of researchers from the Institute of Industrial Science at The University of Tokyo to gain better insights into the internal atomic structure of aluminosilicate glass.
The research team discovered intricate coordination networks between aluminum atoms inside phase-segregated regions. This study could pave the way for achieving optimized glasses that can be used in smart device touchscreens.
With the increase in demand for smartphones, solar panels, and tablets, the demand for tougher, higher-quality, transparent glass will also increase. Aluminosilicate glass—which is made of aluminum, silicon, and oxygen—is one of the candidate materials for such applications.
Similar to all amorphous materials, glass does not form a simple lattice. By contrast, it occurs more like a disordered “frozen liquid.” Yet, complex structures can still form in between, which have not yet been investigated by researchers.
At The University of Tokyo, a research team has now used electron energy loss fine structure spectroscopy in combination with a scanning transmission electron microscope to unravel the local arrangement of atoms inside a glass that is made of 50% silicon dioxide (SiO2) and 50% aluminum oxide (Al2O3).
We chose to study this system because it is known to phase separate into aluminum-rich and silicon-rich regions.
Kun-Yen Liao, Study First Author, Institute of Industrial Science, The University of Tokyo
While using an electron microscope for imaging, a few of the emitted electrons experience inelastic scattering, which makes them lose some of their original kinetic energy.
The amount of dissipated energy differs with respect to the type and location of atom or cluster of atoms within the glass sample on which it impacts. The electron loss spectroscopy technique exhibits sufficient sensitivity to differentiate between the aluminum coordinated in tetrahedral as against octahedral clusters.
The researchers performed pixel-by-pixel fitting of the profile of the fine structure spectra of the electron energy loss to determine the abundance of different aluminum structures with nanometer precision. In addition, they used computer simulations for data interpretation.
Aluminosilicate glasses can be manufactured to resist high temperatures and compressive stresses. This makes them useful for a wide range of industrial and consumer applications, such as touch displays, safety glass, and photovoltaics.
Teruyasu Mizoguchi, Study Senior Author, Institute of Industrial Science, The University of Tokyo
Since aluminosilicate occurs naturally, this method can also be employed for geological studies.
Liao, K., et al. (2020) Revealing Spatial Distribution of Al-Coordinated Species in a Phase-Separated Aluminosilicate Glass by STEM-EELS. The Journal of Physical Chemistry Letters. doi.org/10.1021/acs.jpclett.0c02687.