| 129 I and 119 Sn Mo¨ssbauer spectroscopy, reversibility window and nanoscale phase separation in binary Ge xSe 1 x glasses (2008) | |||||||||||||||
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| range, has received much scrutiny over the years. These glasses have been probed by modulated DSC, Raman scattering, 119 Sn absorption and 129 I emission Mo¨ssbauer spectroscopy, and neutron scattering. The 129 I measurements utilize 129m Te parent as a dopant in glasses, and reveal a bimodal (A, B) distribution of sites, with the site intensity ratio, IB/IA (x), tracking changes in glass structure as a function of x. At low x (o0.15) Senchains are stochastically cross-linked by Ge additive, and IB/IA (x) sharply declines with x. But at x40:15, rigid regions nucleate at the expense of floppy ones, and the ratio IB/IA (x) reverses slope to display a global maximum in the 0:20oxo0:25 range. The latter coincides with the reversibility window usually taken as signature of self-organization of these networks. At x40:26, these glasses enter a stressed-rigid elastic phase and in the 0:31oxo1 3 range nanoscale phase separate into Se-rich and Ge-rich regions. The signature of the latter is saturation of IB/IA (x) at a high value of 1.5 at x 1 3. 119 Sn Mossbauer spectroscopy measurements independently support the picture of broken chemical order of the stoichiometric glass inferred from the 129 IMo¨ssbauer experiments. These observations using local probes are well correlated to Raman scattering, modulated differential scanning calorimetric and diffraction measurements. | |||||||||||||||
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