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.