Tellurite And Fluorotellurite Glasses For Active And Passive

9. Conclusions; MDO 388
• The Ag + concentration profiles were modelled by erfc equations using Mathcad
software, and diffusion parameters obtained (surface concentrations, N0, and
diffusion coefficients, D) if not already known.
9.5. Fibre drawing (Chapter 8)
Stress in fluorotellurite fibre
• Stresses in a proposed core / clad fluorotellurite pair (20 and 25 mol. % ZnF2) due
to thermal expansion mismatch were calculated to be around 72 MPa, relatively
low compared to the tensile strength of the fibre [7].
Viscosity-temperature behaviour
• The viscosity-temperature behaviour of this fluorotellurite core / clad pair was
obtained using thermal mechanical analysis (TMA), and modelled using various
equations [7].
• For a given temperature, the viscosity of the glass increased with decreasing ZnF2,
due to depolymerisation of the TeO2 network with ZnF2 addition [7].
• The Cohen-Grest model showed the best fit and parameters for the viscosity-
temperature behaviour of these glasses, due to their fragile nature [7].
• The fragility of these glasses falls somewhere between fluorozirconate (more
fragile) and oxide tellurite (stronger) glasses [7, 14].