The thermally reversing window in ternary GexPxS1 2xglasses

Ge x P x S 1−2 x glasses in the compositional range have been synthesized and examined in temperature modulated differential scanning calorimetry (MDSC) and Raman scattering experiments. Trends in the non-reversing enthalpy Δ H nr ( x ) near T g show the term to almost vanish in the 0.090(5)< x <0.135(5) range, and to increase by an order of magnitude at x <0.09, and at x >0.135. In analogy to previous results on chalcogenide glasses, we identify compositions at x <0.09 to be elastically floppy , those in the 0.090< x <0.135 range to be in the intermediate phase , and those at x >0.135 to be stressed rigid . MDSC results also show that the Δ H nr term ages in the stressed-rigid and floppy phases but not in the intermediate phase. The intermediate phase is viewed to be a self-organized phase of a disordered network. It consists of at least four isostatically rigid local structures: corner-sharing GeS 4 , edge-sharing GeS 2 , pyramidal P(S 1/2 ) 3 and quasi-tetrahedral S = P(S 1/2 ) 3 units for which evidence comes from Raman scattering. The latter method also shows the existence of P 4 S 7 and P 4 S 10 molecules in the glasses segregated from the backbone. These aspects of structure contribute to an intermediate phase that is significantly narrower in width than in the corresponding selenide glasses.