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Structural relaxation and viscosity of Al2O3 doped magnesium phosphate glasses
Authors: Chromcikova Maria | Hruska Branislav | Nowicka Aleksandra | Svoboda Roman | Liska Marek
Year: 2020
Type of publication: článek v odborném periodiku
Name of source: Journal of Non-Crystalline Solids
Publisher name: Elsevier Science BV
Place: Amsterdam
Page from-to: "120323-1"-"120323-8"
Titles:
Language Name Abstract Keywords
cze Strukturní relaxace a viskozita MgO-P2O5 skel dopovaných Al2O3 Relaxační chování Mg-fosfátových skel dotovaných Al2O3 bylo studováno pomocí termomechnické analýzy a diferenční skenovací kalorimetrie. Viskozity těchto skel byly studovány v rozsahu 10^7 až 10^11 Pa.s. viskozita; strukturní relaxace; fragilita; TMA; Al2O3-MgO-P2O5 skla
eng Structural relaxation and viscosity of Al2O3 doped magnesium phosphate glasses Thermomechanical analysis and differential scanning calorimetry were used to study the viscosity and relaxation behavior of the Al2O3-doped magnesium phosphate glasses. Viscosity in the range (10(7) - 10(11)) Pa center dot s was described by the nowadays top performing multiparametric models. A fixed extrapolation of high-temperature viscosity according to the Eyring theory was applied with the exception of the Arrhenius equation. The activation energies of viscous flow were very close to the activation energy of enthalpy relaxation determined in terms of the Tool-Narayanaswamy-Moynihan model. On the contrary, the activation energy of volume relaxation was found to be much lower in comparison with the viscous flow activation energy. In general, the increase of the Al2O3 content leads to the increases of the viscosity, of the activation energies of viscous flow and structural relaxation (as well as of the kinetic fragilities calculated from these quantities), and of the temperatures characterizing the glass transition during the viscosity, volume, and enthalpy measurements. The phosphate chains interconnecting effect of the Al3+ ions was found to be much stronger than the influence of the MgO modifying oxide. However, the enthalpy changes during the relaxation processes seem to be primarily influenced by the MgO/P2O5 ratio. Consistence of the compositional interpretation of the obtained results indicates the benefits of the utilization of the correlation coefficients for attributing the structural units responsible for the changes of physico-chemical quantities. Viscosity; Structural relaxation; Fragility; TMA; Al2O3-MgO-P2O5 glasses

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