HARDNESS AND THERMAL CONDUCTIVITY OF As-Se-Te CHALCOGENIDE GLASSES

Abstract
The results of the Vickers Hardness (VH) and the thermal conductivity (K) of the As-Se-Te glasses containing : 28.5 - 50 at % As, 5 - 41.4 at % Se, and 0.0 - 57 at % Te are given. A trend in the variation of VH (room temperature) with composition has been observed. The difference in nature and concentration of the chemical bonds between the stoichiometric system, As₂Se₃-As₂Te₃, and the other two alloy systems, AsSe-AsTe and As₂Se₅-As₂Te₅, are used to explain the contrasting results. Below T_g (the glass transition temperature) the thermal conductivity of the glasses increase with temperature. Such increase is pronounced at some compositions. The compositional variation of K for the chalcogenide systems all exhibit a dip in the conductivity at equal proportions of Se and Te. The value of K (20C) of the AsSe_xTe_x glasses varies between 0.18 - 0.95/10^-2/cal/cm.sec.deg. The electronic contribution of the thermal conduction in each system is stimulated with Te, whereas the main mechanism of heat transport is by phonons. So, the increase in K toward the composition ends is controlled by the number of scattering centres in the glass matrix.