Tellurite And Fluorotellurite Glasses For Active And Passive

7. Surface properties; MDO 304
All four etchants from fig. (7.35) produced reasonable etches (i.e. no visible opaque
layer, except nitric acid) compared to 1 and 3M NaOH, HCl and H2SO4. On inspection,
the phosphoric and acetic acids produced an etch of similar quality to HF (no opaque
layer or pitting), and should be investigated further. Weight loss was not measured due to
lack of availability of an electronic balance.
7.2.3. Ion exchange
Fig. (7.36) shows the EDX analysis of glass T08 (80TeO2-9ZnO-10Na2O-1Er2O3 mol.
%), which had a silver layer evaporated on both polished sides (100 and 300 µm),
followed by heat treatment at 285°C for 12 hours under inert atmosphere (argon). The
concentration profile of the 100 µm side was best fitted with an exponential decay curve,
and the 300 µm side by a third order polynomial. The depth of silver was recorded until
the peak was indistinguishable from the EDX spectrum background.
Fig. (7.37) shows the EDX analysis of glass ST08 (79TeO2-5ZnO-10Na2O-5PbO-
1Yb2O3 mol. %), for which one flat side was dipped into a molten salt solution (2AgNO3-
49NaNO3-49KNO3 mol. %) at 270°C for 5 hours.