The Science & Technology
of Glass
Cambridge - Monday 4th to
Wednesday 6th September 2017



Rikiya Kado
<kado.r.aa@m.titech.ac.jp>

article posted 15 June 2017

Rikiya Kado

I am a PhD candidate at Tokyo Institute of Technology. I received BS and MS from Tokyo Institute of Technology. My current research focuses on structure of glass involving molten state and vitrification process.


Structural Feature Induced by MgO substitution for Na2O in Aluminosilicate Glasses and Melts Investigated by High-Temperature Raman Spectroscopy
Rikiya Kado*(1), Tetsuo Kishi(1), Tetsuji Yano(1), Koichi Shiraki(2), Yukihito Nagashima(2), Koichi Sakaguchi(2)

Structures of glasses and melts have been investigated by many researchers because those are deeply correlated with the properties of glass. Especially, aluminosilicate system is one of the interest materials not only in earth science but also in glass science and technology. However, those are not fully understood yet, especially from points of view of structural alternations with composition and temperature. This study gives a focus on the MgO substitution for Na2O in aluminosilicate glass system. Magnesia has been known as one of the key constituents to induce unique properties of glass and glass-ceramics as the materials with small thermal expansivity for structural, thermal or optical uses. The purpose of this study is to clarify the structural role of magnesium component in aluminosilicate glass system and the correlation with its unique properties.

Glass samples with the compositions of 6.6xNa2O–(33-6.6x) MgO-12Al2O3-55SiO2 in mol%, where x = 0~5, were prepared by melt quenching method. The prepared glass sample was re-melted in a Pt crucible at 1600 °C using a compact electric resistance furnace for Raman spectroscopy, and nanosecond Q-swithced SHG Nd:YAG laser ( λ = 532 nm) pulses were irradiated onto the melt in the crucible. Collection of Raman signals was carried out at the temperatures from 1600 °C to room temperature at intervals of 100–200 K.

The main Raman bands appear in high wavenumber region which are attributed to the silicate units with different connectivities to other structural units. MgO substitution is found to induce a characteristic band at around 1200 cm-1. This band intensity increases with MgO substitution (Fig. 2). From the comparison with the previous data on cordierite (2MgO·2Al2O3·5SiO2) crystal[1], in which quantum-mechanical calculations of crystal model has been made to identify the experimental Raman bands, the observed high-frequency band is ascribed to the vibration of the dimer of SiO4 tetrahedra connected with three AlO4 tetrahedra. This reveals that Mg2+ ions strongly interact with AlO4 tetrahedra to form unique Al-rich cluster similar to that found in cordierite crystal. Since this structural feature is observed in Raman spectra of glass melts at high temperature, MgO plays an important role to affect glass network in wide temperature range from melting temperature to room temperature.

Reference:

[1] R. Kaindl, D. M. Tobbens, U. Haefeker, Quantum-mechanical calculations of the Raman spectra of Mg- and Fe-cordierite, Am. Mineral., 96 (2011) 1568

Institutions:

(1) Tokyo Insutitute of Technology, Meguro-ku, Tokyo 152-8550 Japan
(2) Nippon Sheet Glass Co., Ltd. Itami, Hyogo 664-8520 Japan