Tellurite And Fluorotellurite Glasses For Active And Passive

2. Literature review; MDO 52
and suppresses the movement of Na + and Zn 2+ ions resulting in a high resistance to
crystallisation [52].
Feng et al. [53] studied hydroxyl absorption of glasses in the system TeO2-Na2O-ZnO-
GeO2-Y2O3-Er2O3. Two absorption bands due to OH were prominent in these glasses,
one at 3500 cm -1 (2.86 µm) attributed to free OH and one at 2300 cm -1 (4.35 µm)
attributed to hydrogen bonded OH (the stronger the association the longer the wavelength
of absorption). Bubbling CCl4 through the molten glass reduced the intensity of both
absorption bands as OH was removed from the glass as HCl. Fig. (2.12) illustrates this
showing the infrared spectra of an untreated (A: melted at 950°C in air for 2 hours), and
treated melt (E: melted at 950°C in air for 1.5 hours, and bubbled with dry air and CCl4
for 30 min.).
Fig. (2.12): Infrared spectra of TeO2-Na2O-ZnO-GeO2-Y2O3-Er2O3 glass untreated (A:
melted at 950°C in air for 2 hours), and treated melt (E: melted at 950°C in air for 1.5
hours, and bubbled with dry air and CCl4 for 30 min.) [53].