Raman and DSC studies of fragility in tellurium-zinc oxide glass formers
Résumé
Raman scattering and differential scanning calorimetry (DSC) measurements have been carried out in four mixed (TeO2)1-x(ZnO)x (x = 0.1, 0.2, 0.3, 0.4) glasses at high temperatures (Raman and DSC through the glass transition) and high pressures (Raman) with the aim of determining the fragility of these glass forming oxides. Four different criteria, corresponding to four parameters, were applied to assess the fragility of the glasses. From the DSC studies, we have obtained the fragility parameter m which corresponds to the slopes of Arrhenius (lnQ vs. 1/Tg, were Q is the heating rate) plots, and the glass transition width ΔTg. Also, from the low-frequency Raman scattering, and in particular the boson peak intensity of the glasses at Tg, we have estimated the fragility ratio rR (Tg) = Imin/Imax whose value serves as another (empirical) fragility criterion. Finally, from high pressure Raman measurements on the glasses, we have estimated the Grüneisen parameter γT for each glass, which constitutes the fourth fragility parameter adopted in this work. Considering the four parameters ΔTg, m, r(Tg) and γT and the generally accepted (empirical) fragility criteria, we conclude that the mixed tellurium-zinc oxides constitute strong-to-intermediate glass formers.