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Tellurite And Fluorotellurite Glasses For Active And Passive

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4. Thermal properties and glass stability; MDO 112<br />

Fig. (4.21) shows variation of Tg and Tx-Tg with melting time for glass preforms<br />

MOF005vi, vii and viii. These glasses were melted in a gold crucible, calculated to give a<br />

30g batch, for half the melting time at 800°C, the remainder at 670°C, then cast into a<br />

cylindrical brass mould (ID = 1 cm) and annealed for 1 hour at 230°C (see chapter 3).<br />

T x -T g / o C<br />

T g / o C<br />

245<br />

244<br />

243<br />

242<br />

241<br />

240<br />

239<br />

238<br />

237<br />

236<br />

235<br />

234<br />

233<br />

4 5 6 7 8 9 10 11 12 13<br />

167<br />

166<br />

165<br />

164<br />

163<br />

162<br />

161<br />

160<br />

159<br />

158<br />

157<br />

156<br />

155<br />

Melting time / hours<br />

4 5 6 7 8 9 10 11 12 13<br />

Melting time / hours<br />

Fig. (4.21): Variation in (a) Tg and (b) Tx-Tg with melting time for glass preforms<br />

MOF005vi, vii and viii (70TeO2-10Na2O-20ZnF2 mol. %).<br />

(a)<br />

(b)

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