Page 61 - Chalcogenide Glasses for Infrared Optics

Chalcogenide Glasses 39

making the measurements. With a criterion, at this early stage, of an
absorption coefficient of less than 1 cm , the Si-Ge-As-Te glass was
–1
judged good from 2.5 to 12.5 µm. The Si-As-Te glasses were judged
good to only 9 µm, and the Ge-As-Te glasses good from 2.5 to 20 µm.
Blending of two ternary systems was carried out for six combina-
tions. The one that produced the most useful results was the Si-As-Te
with the Ge-As-Te system. Table 2.4 lists the compositions prepared

Sample Softening Point Hardness
No. Composition (°C) (Knoop)
239 Si As Te 196 108.4
6 8 26
242 Si GeAs Te 190 126.5
5 8 26
245 Si Ge As Te 124 126.5
4 2 8 26
248 Si Ge As Te 200 136.8
3 3 8 26
251 Si Ge As Te 190 127.0
2 4 8 26
253 SiGe As Te 180 126.5
5 8 26
255 Ge As Te Crystalline —
6 8 26
258 Si As Te 160 108.4
6 9 45
260 Si GeAs Te 136 105.8
5 9 45
261 Si Ge As Te 148 110.9
4 2 9 45
262 Si Ge As Te 146 108.7
3 3 9 45
263 Si Ge As Te 148 109.0
2 4 9 45
264 SiGe As Te 150 113.4
5 9 45
265 Ge As Te 162 113.7
6 9 45
240 Si As Te 310 166.9
5 5 10
266 Si GeAs Te 290 156.5
4 5 10
267 Si Ge As Te 293 179.0
3 2 5 10
268 Si Ge As Te 256 151.2
2 3 5 10
269 SiGe As Te Crystalline —
4 5 10
241 Si As Te 434 207.8
7 5 8
244 Si GeAs Te 380 195.6
6 5 8
247 Si Ge As Te 394 198.6
5 2 5 8
250 Si Ge As Te 379 195.0
4 3 5 8
251 Si Ge As Te Crystalline —
3 4 5 8
TABLE 2.4 Blended Glasses Formed from the Ternary Systems Si-As-Te and Ge-As-Te