Crucial effect of melt homogenization on the fragility of non-stoichiometric chalcogenides.
The kinetics of homogenization of binary AsxSe100 - x melts in the As concentration range 0% < x < 50% are followed in Fourier Transform (FT)-Raman profiling experiments, and show that 2 g sized melts in the middle concentration range 20% < x < 30% take nearly two weeks to homogenize when starting materials are reacted at 700 °C. In glasses of proven homogeneity, we find molar volumes to vary non-monotonically with composition, and the fragility index M displays a broad global minimum in the 20% < x < 30% range of x wherein M < 20. We show that properly homogenized samples have a lower measured fragility when compared to larger under-reacted melts. The enthalpy of relaxation at Tg, ΔHnr(x) shows a minimum in the 27% < x < 37% range. The super-strong nature of melt compositions in the 20% < x < 30% range suppresses melt diffusion at high temperatures leading to the slow kinetics of melt homogenization.
School of Electronics and Computing Systems, College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio 45221-0030, USA.
Sriram
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Ravindren
School of Electronics and Computing Systems, College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio 45221-0030, USA.
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K
Gunasekera
School of Electronics and Computing Systems, College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio 45221-0030, USA.
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Z
Tucker
Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221-0011, USA.
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A
Diebold
School of Electronics and Computing Systems, College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio 45221-0030, USA.
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P
Boolchand
Laboratoire de Physique Théorique de la Matière Condensée, Université Pierre et Marie Curie, 4 Place Jussieu, F-75252 Paris Cedex 05, France.
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M
Micoulaut