The structural properties of Ge<inf>x</inf> Sb<inf>40-x</inf> Se<inf>60</inf> system

Abstract

High purity glasses with an average coordination number Nc in the GexSb40-xSe60 ternary system between 2.4 and 2.7, were prepared under vacuum with x = 0, 10, 20 and 30. X-ray diffraction (XRD) as, well as the Differential Scanning Calorimetry (DSC) studies were carried out to identify the amorphous and polycrystalline structure for the Ge-Sb-Se system. The dependence of properties such as the mean atomic volume Va, the glass transition temperature Tg and the number of topological constraints Ncon were studied as a function of Nc, in the light of recent model proposed for covalent random network. The occurrence of this dependence in addition to those due to topological effects leads to the conclusion that the effects of chemical ordering and the effect, which have topological origin, coexist in this system. To understand the effect of Nc on the glass-forming capability, the number of lone-pair electrons, (Ncs - Nc/2, and the efficiency of the structural modification ΔΦ were calculated and discussed in relation to topological consideration. This then renders support to Phillips' theoretical model. © 2005 Springer Science + Business Media, Inc.