Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 306
The first point was left out of the exponential decay fit, as this lower at. % silver value at
0 µm was most likely due to the presence of the surface attack from the molten salt,
resulting in many voids, and heavy pitting (ridges spaced around 0.5 mm) at the glass
surface, producing a spurious value.
7.3. Discussion
7.3.1. X-ray photoelectron spectroscopy (XPS)
7.3.1.1. XPS of ZnF2 powder
Fig. (7.5) and (7.6) show the low resolution XPS spectra of ZnF2 powder used in this
study before and after fluorination. As expected, the oxygen levels were significantly
reduced by this treatment [7]. This can be seen from table (7.3), which summarises the
quantitative analysis from the high resolution scans. If it is assumed that all of the oxygen
in the powders was within the Zn(OH)F phase identified by XRD in chapter 5, it is
possible to calculate the proportion of Zn(OH)F and ZnF2 in the powders before and after
fluorination. Zn(OH)F is composed of 33.33 at. % zinc, 33.33 at. % OH (i.e. oxygen),
and 33.33 at. % fluorine. ZnF2 is composed of 33.33 at. % zinc, and 66.67 at. % fluorine.
Therefore, 13.22 at % O1s XPS peak from table (7.3), results from 39.67 mol. %
Zn(OH)F and 60.33 mol. % ZnF2. For the fluorinated sample, the 3.12 at. % O1s XPS
peak from table (7.3), results from 9.35 mol. % Zn(OH)F and 90.65 mol. % ZnF2. This is