Influence of connectivity on the rigidity of the covalently bonded (GeTe4)100−x(As2Se3)x glasses

Bulk (GeTe4)100−x(As2Se3)x(0≤x≤60) glasses in the tie-line GeTe4-As2Se3prepared by melt quenching method are characterized by differential scanning calorimetry (DSC), X-ray diffraction and Raman spectroscopy. In covalent network glasses, the structural network transform from a floppy to a rigid structure at an average coordination number (Zav) 2.40. (GeTe4)100−x(As2Se3)x glasses in the range 5≤x≤15 exhibit two stage crystallization whereas glasses with x>15 exhibit single stage crystallization. Annealing of the glasses results into hexagonal GeTe and Te structures for 0≤x≤10 whereas glasses in the range 15≤x≤40 show only Te crystallites. For higher As2Se3 mol. % (x≥50) As2Te3 phase along with Te has been observed. Raman studies indicate the presence of GeSe2, GeTe2, As2Te3, and -Te-Te-structural units. The average coordination number of the glasses prepared in this tie-line is 2.4. Though the overall bond energy of the system increases with the increase of As2Se3, the density (ρ), glass transition (Tg) and specific heat capacity (∆Cp) show a decreasing trend. The rate of decrease of ρ, Tg and ∆Cp is slow for 0≤x