Transition threshold in Ge_xSb₁₀Se_90-x glasses

Ge_xSb₁₀Se_90-x glasses with Ge content from 7.5 to 32.5at.% have been prepared by melt-quench technique, and the physical parameters including glass transition temperature (T_g), density (ρ), compactness (C), shear elastic moduli (C_s), compression elastic moduli (C_c), refractive index (n), and optical bandgap (E_g) have been investigated. While all these physical parameters show threshold behavior in the glass with a chemically stoichiometric composition. Raman spectra analysis also indicates that, with increasing Ge content, Se-chains or rings gradually disappear until all Se-atoms are consumed in the glass with a chemically stoichiometric composition. With further increasing Ge content, homopolar Ge-Ge and Sb-Sb bonds are formed and the chemical order in the glasses is violated. The threshold behavior of the physical properties in the Ge_xSb₁₀Se_90-x glasses can be traced to demixing of networks above the chemically stoichiometric composition.