Dresden 2017 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 56: Topical session: Dynamics, relaxation and deformation in deeply supercooled metallic liquids and glasses - kinetic transitions
MM 56.3: Vortrag
Donnerstag, 23. März 2017, 11:00–11:15, IFW A
Fragile-strong liquid transitions and the underlying structural transitions in chalcogenide glassformer Ge15Te85 and bulk metallic glass-forming liquids — •Shuai Wei1, Moritz Stolpe2, Oliver Gross2, William Hembree2, Simon Hechler2, Jozef Bednarcik3, Ralf Busch2, Pierre Lucas4, and C.Austen Angell1 — 1Arizona State University, Tempe, USA — 2Saarland University, Saarbruecken, Germany — 3DESY, Hamburg, Germany — 4University of Arizona, Tucson, USA
A striking anomaly in the viscosity of chalcogenide glass-forming alloy Ge15Te85 is reminiscent of the equally striking comparison of liquid tellurium and water. Applying the Adam-Gibbs viscosity equation to calorimetric data, we find a fragile-to-strong liquid transition (FS-transition), and then predict the "strong" liquid course of the viscosity down to Tg at 406 K. The extrapolation is in good agreement with a direct measurement of fragility near Tg using differential scanning calorimetry. The in-situ X-ray scattering data reveal that the transition is not only related to short-range-order (SRO) structural change, but also linked to a remarkable development of medium-range-order (MRO). The latter manifests as an emerging pre-peak in total structural factor S(Q) and an atomic pair correlation on the length scale of ~8 Å in the real-space G(r) function. The FS-transitions at high pressures are examined in terms of experimental data and the Ehrenfest relation. Finally, we compare the behavior of Ge15Te85 with the liquid-liquid transition in the bulk metallic glass-forming liquid, Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 (Vit.106a).