Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 326
Therefore, the glass would probably not reach thermal equilibrium during the duration of
the experiment, to the extent of the samples heat treated in a furnace. This could result in
the sharper diffusion profile seen in fig. (7.41).
Table (7.9) summarises the parameters from equation (7.14) for all three ion-exchange
models.
Table (7.9): Parameters for ion-exchange models, where N0 = fraction of silver at glass
surface (from EDX data), t = time of experiment, and D = diffusion coefficient.
Parameter
T08 300 µm
Glass
T08 100 µm ST08 molten salt
N0 0.0242 0.0228 0.1250
t / ×10 4 sec. 4.32 4.32 1.80
D / ×10 -6 m 2 .s -1 25.21 10.58 14.38
7.4. Summary
XPS of as-recived and fluorinated ZnF2 powders showed ‘oxygen’ levels were reduced
from around 13 to 3 at. %, and the level of Zn(OH)F from around 40 to 9 mol. % on
fluorination [7]. The level of Zn(OH)F may be lower if molecular water and organic
contaminants were present.
XPS of tungsten-tellurite, and fluorotellurite glasses showed a multi-peak structure to
the O1s peak, thought to be due to the following with increasing binding energy: BOs /
NBOs, OH, C-O, and M=O species. The OH component was relatively small on spectra
from cleaved glass surfaces, however this grew significantly on optically polished
surfaces, due to degradation on exposure to atmospheric moisture. This degradation also