Tellurite And Fluorotellurite Glasses For Active And Passive

4. Thermal properties and glass stability; MDO 89
has no fundamental meaning. The solidus and liquidus temperatures (Ts and Tl
respectively) were obtained by the same interpolation method as Tg described above. Fig.
(4.5) illustrates this.
←← Endothermic ∆∆T / °C Exothermic →→
T s
450 460 470 480 490
Temperature / °C
Fig. (4.5): DTA trace of glass MOF005 (70TeO2-10Na2O-20ZnF2 (mol. %)), showing
interpolation of the solidus temperature, Ts, and liquidus temperature, Tl.
Transformations of this kind (melting) are reversible and obey Le Chatelier’s principle
[4] which implies, for example, that ice-water will stay at 0°C until it fully transforms to
ice or water. Any heat added to the system contributes to the phase change rather than a
change in temperature, as long as both phases exist. For this reason melting
transformations have a distinct shape in DTA traces.
In a DTA scan at constant heating rate, where a solid sample fuses, the reference
sample increases in temperature at the preprogrammed heating rate, while the sample
temperature remains at the melting temperature until the transformation is complete.
Therefore, when ∆T vs. reference temperature is plotted, a linear deviation from the
T l