Tellurite And Fluorotellurite Glasses For Active And Passive

2. Literature review; MDO 57
A number of the compositions series in table (2.5) were melted in ceramic crucibles
(silica, alumina or zirconia) which will inadvertently improve glass stability as some
unwanted oxide will be taken into solution in the glass melt, but will affect optical
properties (the IR-edge will be blue-shifted).
2.5.2.2. Thermal properties
The properties of fluorotellurite glasses in the early work by Stanworth [14] were
reported in section 2.3.1.
Table (2.6) summarises the characteristic temperatures and Hruby’s thermal stability
parameter (KH) [63] of the glasses reported by Durga et al. [62].
Table (2.6): Thermal properties of the Cr 3+ doped ZnF2-MO-TeO2 (MO = P2O5, Bi2O3 or
As2O3 ) glasses [62].
Glass (mol. %) Tg/°C Tc/°C Tm/°C Tc-Tg/°C KH
50TeO2-9.6As2O3-40ZnF2-0.4Cr2O3 617 721 1081 104 0.289
50TeO2-9.6Bi2O3-40ZnF2-0.4Cr2O3 595 679 1126 84 0.188
50TeO2-9.6P2O5-40ZnF2-0.4Cr2O3 625 695 1145 70 0.155
The glass containing As2O3 was the most thermally stable of the three.
Nazabal et al. [30] showed that thermal stability increased initially with ZnF2 addition
to TeO2-ZnO glasses, however, further increases in stability with ZnF2 were not
significant and within the errors of the DTA experiments. Table (2.7) summarises these
characteristic temperatures, with glass density (ρ), and electronic absorption edge (λc).