Tellurite And Fluorotellurite Glasses For Active And Passive

2. Literature review; MDO 48
Braglia et al. [48] performed a detailed thermal stability and viscosity-temperature
study of a series of glasses which are shown in table (2.3) with their characteristic
temperatures measured by DSC.
Table (2.3): Characteristic temperatures of TeO2-ZnO-Na2O glasses [48].
TeO2
/mol. %
ZnO
/mol.%
Na2O
/mol. %
Er2O3
/ppmw
Tg/°C Tx/°C (Tx-Tg)/°C
76.58 20.42 3 1,000 313 452 139
75.00 20.00 5 1,000 302 440 138
74.00 20.00 6 1,000 302 456 154
72.63 19.37 8 - 297 472 175
71.05 18.95 10 1,000 298 474 176
From table (2.3), addition of Na2O decreases Tg as expected and opens up the Tx-Tg gap
(i.e. increases glass stability). The glass (mol. %) 74TeO2-20ZnO-6Na2O (with 1,000
ppmw Er2O3) was subsequently heat treated at Tx (456°C, time not stated) to crystallise
the sample, and analysed by X-ray diffraction (XRD). Fig. (2.9) shows the XRD trace of
this sample.
Fig. (2.9): XRD trace of glass 74TeO2-20ZnO-6Na2O (with 1,000 ppmw Er2O3), before
and after heat treatment at 456°C (time not stated) [48].