The temperature dependence of Vickers hardness between room temperature and around the glass transition temperature Tg in a vacuum for some glasses with different fragile characters was measured. The hardness at T/Tg<0.9 decreases gradually with increasing temperature, but the glasses show unique temperature dependences in the range 0.9<T/Tg<1.1 depending on their fragile character. A sharp decrease in hardness is observed at around T/Tg=0.9-1.0 for fragile Bi2O3- and TeO2-based glasses, but 50CuOx·50P2O5 and soda-lime silicate glasses with strong viscosity characteristics still have relatively large Vickers hardness even at Tg and the hardness drops to almost zero around T/Tg=1.05-1.1. It is suggested that for fragile glasses the β-relaxation has an important effect on the Vickers hardness change near the glass transition region, but for strong glasses it is the α-relaxation that governs the hardness near Tg.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry