Tellurite And Fluorotellurite Glasses For Active And Passive

5. Crystallisation studies; MDO 149
Table (5.7): Ten most intense peaks with corresponding 2θ (observed and theoretical) and
Miller indices for deposit left on the silica liner and lid after melting glass MOF005
(70TeO2-10Na2O-20ZnF2, mol. %) for 12 hours at 800°C in glovebox.
Observed
2θθθθ / °
Observed
intensity / %
Theoretical
2θθθθ / °
Theoretical
intensity / %
hkl
JCPDS
Card
22.00947 23.0 21.86131 8 101 42-1365
25.90481 17.8 - - - -
26.38511 98.1 26.20208 95 110 42-1365
26.67667 22.3 - - - -
28.93278 20.1 28.75441 14 111 42-1365
30.11162 100.0 29.94866 100 102 "
37.54363 22.2 37.36155 15 200 "
48.69993 64.3 48.52443 47 212 "
55.29621 23.7 55.12931 19 114 / 221 "
62.03630 15.1 61.85459 10 204 / 311 "
5.2.1.3. XRD of glasses which crystallised during processing or characterisation
During melting
A batch of glass MOF001 (65TeO2-10Na2O-25ZnF2, mol. %) was melted in the fume
cupboard, with fluorinating agent (see section 3.4) added to dry the batch further (1 g of
(NH4)HF2 to 1 g of batch). However, after melting a 10g batch for 5 hours in a platinum
crucible at 800°C, and dropping to 700°C to cast, most of the melt had volatilised,
leaving behind around 5g of a white solid deposit in the crucible. Fig. (5.10) shows the
XRD trace of this deposit. It can be seen from this trace, that a glass-ceramic has resulted
from this treatment. An amorphous ‘halo’ can be seen at around 30° 2θ, and the presence
of crystalline material. The closest match to the crystalline peaks was JCPDS card
number: 20-1182: sodium zinc fluoride NaZnF3, orthorhombic, space group Pbnm. Table