The influence of Mg substitution for Al on the properties of SiMeRE oxynitride glasses

The thermal mechanical properties of 60Si20Mg20RE (RE: rare earth) oxynitride glasses can be tailored by the substitution of rare earths of decreasing ionic size. The Young's modulus, hardness, glass transition temperature and viscosity all increase with the substitution La by Gd and Gd by Lu while the thermal expansion coefficients decrease. Compared to the 55Si25Al20RE oxynitride glasses, replacement of At by Mg lowers the glass transition temperatures and viscosities and raises the thermal expansion coefficients substantially. On the other hand, the Young's moduli are higher in the Mg-bearing glasses. These behaviors are seen to be a result in changes in the nature of the bonding in the glass structure. (C) 2003 Elsevier B.V. All rights reserved.