Compositional dependence of the boson peak and fractal dimensionality in Calcium Aluminate glasses prepared by aerodynamic levitation and CO2-laser melting

Deconvoluting interrelationships between low‐energy vibrational modes and elastic properties in CaO–Al2O3 glasses

“…The BP dominates over low-lying vibrational bending modes in the low-frequency regime of the Raman spectra and its characteristic frequency is strongly depended on altering CaO content. 25 If one considers the harmonic approximation for the Stokes-side Raman spectra that is collected by amorphous materials, it was shown by Shuker and Gammon 41 that the Raman intensity can be written as follows:…”

“…This technique has proven to be the "technique of choice" when it comes to vitrify glassy compositions exhibiting either high melting temperatures 34,35 or to expand the glass formation region achieved so far with conventional melt quenching techniques. 25,32 The ADL technique is executed in two distinct steps for the "homemade" levitator setup. 36,37 First, small amounts, usually a few milligrams (<10 mg) of the glass compositions intended for vitrification, still in fine grain powder form, are placed on a water-cooled copper hearth for initial melting.…”

“…Similar efforts proposed a model aiming to unify the experimental data produced by spectroscopic and diffraction experiments of amorphous solids 23,24 However, despite systematical efforts to investigate the origin of the BP, it remains debatable and especially for CA has just started to be systematically investigated. 25 Most studies, so far, that have dealt with the elucidation of structure-property relations for oxide glasses have looked systematically into the compositional dependence of the above-mentioned linkage. Even less attention has been given to the linkage between the compositional dependence of the BP and the elastic properties of the corresponding glasses.…”

“…The ADL technique combined with CO 2 laser melting has been proven a very versatile and quite reliable technique that can provide homogeneous glasses, while at the same time expanding the established glass formation region due to the extremely high cooling rates achieved during synthesis. 25,31,32 ADL is the use of gas pressure to levitate materials so that they are no longer in physical contact with any container. In scientific experiments, this removes contamination and nucleation issues associated with physical contact with a container.…”

“…As crystal nucleation is suppressed by levitation and it is not limited by any other requirement (e.g., sample conductivity in the case of electromagnetic levitation), ADL can be used to prepare glassy materials, from high-temperature melts that cannot be made by standard methods. 25,31,32 The above-mentioned expansion in the established glass forming region, is extremely important as the explosion in the interest shown in glasses and amorphous materials due to their extensive use in technology-related devices and applications, calls for an ever-evolving effort for novel glasses with novel compositions and properties. 33,34 Here, we report evidence that shed light on the intriguing linkages between the low-frequency vibrational modes in CA glasses, namely, the BP behavior and how this behavior is connected to the elastic properties of CA glasses.…”