The Intermediate Phase in Ternary Ge_xAs_xSe_(1-2x) Glasses

摘要

Melt-quenched As_xGe_xSe_(1-2x) glasses over the composition range, 0 < x < 0.26, are examined in Raman scattering, T-modulated Differential Scanning Calorimetry (MDSC), and ~(119)Sn Mossbauer spectroscopy measurements. The non-reversing enthalpy near T_g, ΔH_(nr)(x), accessed from MDSC shows a global minimum (～ 0) in the x_c(1) = 0.09 < x < X_c(2) = 0.16 range, and increases by an order of magnitude both at x < x_c(1) and at x > X_c(2). Raman mode frequency of corner-sharing Ge(Se_(1/2))_4 tetrahedra studied as a function of x, also shows three distinct regimes (or power-laws, p) that coincide with AHm(x) trends. These regimes are identified with mechanically floppy (x < X_c(1)), intermediate (x_c(1) < x < x_c(2)), and stressed-rigid (x > x_c(2)) phases. The Raman elasticity power-law in the intermediate phase, p_1 = 1.04(3), and in the stressed rigid phase, p_2= 1.52(5), suggest effective dimensionalities of d = 2 and 3 respectively.