The role of chemical composition and mean coordination number in Ge-As-Se ternary glasses

Abstract

We prepared a series of Ge-As-Se glasses with different chemical compositions and mean coordination numbers (MCN) from 2.2 to 2.94. We further measured their physical properties in order to understand the effect of MCN and chemical compositions on the physical properties of the glasses. It was found that, while glass transition temperatures, Tg, in the glasses with stoichiometric compositions generally increase linearly with increasing MCN, they depart from the linear behaviour in the glasses with high MCN >2.6 and low MCN<2.4. The fluctuation of Tg is less than 5% in the glasses with the same MCN of 2.5 but different chemical compositions. On the other hand, the density and elastic moduli of the glasses show two transition thresholds at MCN=2.45 and 2.65, respectively. The glasses with the same MCN of 2.5 but different chemical compositions show a change of 3% in density and 5% in elastic moduli, respectively. All these results suggest that, in a region from MCN=2.4 to 2.55, MCN could be a primary factor to determine the physical properties of the ternary glasses.