Tellurite And Fluorotellurite Glasses For Active And Passive

8. Fibre drawing; MDO 341
Table (8.4): Parameters of viscosity models for glasses MOF001 (65TeO2-10Na2O-
25ZnF2 mol. %) and MOF005 ((70TeO2-10Na2O-20ZnF2 mol. %), and predicted fibre
drawing temperatures (Tη4.5).
Glass Model A B C T 0 / °K Tηηηη4.5 / °C
Arrhenius -27.98 1.94×10 4 - -
MOF001 clad
(25 mol. % ZnF2)
MOF005 core
(20 mol. % ZnF2)
VFT -7.39
3.06×10 3
- 341.28
CG -4.32 737.22 18.68 647.41
ML -7.98 902.96 2.75×10 3 347.64
Arrhenius -28.61 2.00×10 4 - -
VFT -29.94 2.16×10 4 - -22.04
CG -6.73 753.71 25.05 764.87
ML -36.73 3.52×10 3 2.72×10 4 -162.67
The VFT and ML models were not used to predict fibre drawing viscosities, as they
generated nonsensical parameters for the core glass, such as negative Kelvin values for
T0.
8.2.3. Crystals in drawn fibre
The ESEM (environmental scanning electron microscopy) and EDX (energy dispersive
X-ray) analysis techniques are described in section 7.1.3.1. Fibre of composition
MOF005ii (70TeO2-10Na2O-20ZnF2 mol. %), which crystallised on drawing is reported
here (i.e. all ESEM micrographs shown were taken from one drum of fibre), and EDX
results of fibre MOF005ii (70TeO2-10Na2O-20ZnF2 mol. %) are also tabulated.
Fig. (8.7) shows an ESEM micrograph of triangular shaped crystals near the surface in
unstructured glass fibre of composition MOF005ii (70TeO2-10Na2O-20ZnF2 mol. %),
diameter around 200 µm. The fibre was mounted length-ways in epoxy resin, and cross-
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