We have investigated thermal properties of bulk Si15Te85-xAgx (4 ≤ x ≤ 20) glasses in detail, through alternating differential scanning calorimetry experiments. The composition dependence of thermal parameters reveal the signatures of rigidity percolation and chemical threshold at compositions x = 12 and x = 19, respectively. The stability and glass forming ability of these glasses have also been determined using the data obtained from different thermodynamic quantities and it is found that the Si15Te85-xAgx glasses in the region 12 ≤ x ≤ 17 are more stable when compared to other glasses of the same series. Further, the blueshift observed in Raman spectroscopy investigations, in the composition range 12 ≤ x ≤ 13, support the occurrence of stiffness threshold in this composition range. All Si15Te85-xAgx (4 ≤ x ≤ 20) glasses are found to exhibit memory type switching (for sample thickness 0.25 mm) in the input current range 3–9 mA. The effect of rigidity percolation and chemical thresholds on switching voltages are observed at x = 12 and 19, respectively.

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A new phase-change memory material, in bulk, has been prepared by melt-quenching technique, which has a better glass forming ability. This sample is set and resettable relatively easily for several cycles at 2mA SET and RESET input currents, and is likely to be a suitable material for phase-change memory applications. Raman scattering studies have been undertaken during the SET and RESET operations to elucidate the local structural transformations that occur during these operations

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Te-rich Si15Te85-xGex (1 ≤ x ≤ 11) glasses are found to exhibit an anomalous phase separations with germanium composition. The structural transformation of o-GeTe crystalline phase from o-GeTe with a = 11.76 Å, b = 16.59 Å, c = 17.44 Å, to high pressure o-GeTe with a new reduced lattice parameters a = 10.95 Å, b = 4.03 Å, c = 4.45 Å, is observed at Tc3 in the composition range 6 ≤ x ≤ 11. Raman studies support the possible existence of high pressure o-GeTe phase which is observed in X-ray diffraction experiments